Flexible manufacturing system pdf

 

    ١. Introduction. A flexible manufacturing system (FMS) is a manufacturing system in which there is some amount of flexibility to react in the case of changes. PDF | Flexible manufacturing system is a system that is able to respond to changed conditions. In general, this flexibility is divided into two key categories and. PDF | On Jan 1, , J. Browne and others published Classification of Flexible Manufacturing Systems.

    Author:MERLE HIRAOKA
    Language:English, Spanish, Dutch
    Country:Morocco
    Genre:Science & Research
    Pages:634
    Published (Last):04.03.2016
    ISBN:336-3-52458-156-8
    Distribution:Free* [*Sign up for free]
    Uploaded by: LACY

    52693 downloads 158749 Views 39.63MB PDF Size Report


    Flexible Manufacturing System Pdf

    Abstract: Flexibility in manufacturing system is one of the most important issues of present scenario, to fulfill the desired customer's requirement & getting low. Formerly Flexible Manufacturing System used to form a small part of Computer Integrated Manufacturing, but at present it is taught as an elective for UG students . switch over to flexible manufacturing systems (FMSs) as a viable means to term flexible manufacturing system, or FMS, refers to a highly automated GT.

    Taking the MDH50 precision machining center as a example, this paper established the flexible body of five key components, bed, column, spindle boxes, slipway and worktable, and built the rigid-flexible coupling systems of whole machine, based on the basic theory of multi-body system dynamics. Then the cutting force reference to the actual constraints was applied to the system and the dynamics simulation was carried out. The effect of every component on machining precision was effectively identified. Dynamic stiffness testing of the machine is based of principles of testing the transmission components dynamic stiffness, and further analysis of the each component dynamic stiffness is conducted, which can verify the accuracy of flexible body analysis. According to the engineering drawings and the given diameter of holes, the position of holes can be determined automatically. Based on the type of tools, the depth of counterbore holes, the depth of pre-manufactured holes and cutting parameters, the program of boring was generated automatically. Following the program, the process system can complete the rough boring, the finish boring, dwelling or without dwelling at downhole. It briefly analyzes the characteristic and applicability of Expert System, Neural Network, Fault Tree Analysis, Fuzzy Set Theory and Multi-Agent System, and points out the key technical problems which is needed to be solved in this field. Then it views the future development, and points that the fault diagnosis of integrated intelligence and remote network is the research and development trend of diagnosis system for CNC Machine. Chang, William R. Peterson Abstract: Increasing global competition, shrinking product life cycles, and increasing product mix are defining a new manufacturing environment in world markets. Various design and performance parameters are evaluated and compared for the original and the improved FMS. The results obtained by this method may be useful to other researchers for similar types of applications.

    However, over the last several years, various high-tech methods have emerged or have been perfected to deal with the problem of automating and reducing the manual effort required for burr removal. The 4 most common types of automated deburring are: Mechanical 2. Vibratory 3. Thermal energy 4.

    In many cases, conventional robots are not ideally suited for burr removal. Also many work pieces require different parts of the work piece. Parts systematically enter a large bowl container filled with ceramic pebbles commonly referred to as media. The size of the ceramic pebbles commonly referred to as media. The size of the ceramic media can vary depending upon the type, size and material of the parts to be deburred. As the parts enter the bowl via conveyor , the bowl is rapidly vibrated back and forth, this motion agitates the parts in the ceramic media, removing burrs, and gently polishing the parts.

    Here eccentric weights are mounted on each end of the bowl support shaft to vibrate the bowl in a controlled and adjustable manner. The parts to be deburred are sealed in a chamber, which is pressurized with a mixture of combustible gas and oxygen. This mixture completely envelops the parts and surrounds the burrs, regardless of external internal or blind hole location. This gaseous mixture is then ignited by a spark plug, which creates an instant burst of intense heat, and burrs, because of their high ratio of surface to area mass, burst into flames.

    Burrs and flash are instantly oxidized and converted to powder in approximately 25 to 30 seconds. Parts are then cleaned with a solvent. This process removes undesired material from all surfaces and eliminates follow-up inspection necessitated by inconsistent hand deburring operations. This process is effective for wide range of dissimilar parts of both ferrous and nonferrous materials. In this process an electrode is positioned close to area of workpiece made of conducting material to be deburred.

    The electrode is connected to the negative, and the work piece to the positive terminal of a D. An electrolyte is made to flow between electrode and workpiece. Thus electrochemical reaction takes place and burrs are removed. In this the current passed is directly proportional to burr removal rate. This process has several advantages like tool never touches the part, so no tool wear occurs. No heat is created during the process; therefore, thermal or mechanical stress cannot distort the part.

    Deburring and Wash Stations 49 6. Wash stations are automated high-tech washing machine that uses high-pressure coolant to remove the dirt, grease and chips from the part, fixture and pallet. Wash stations can accommodate a variety of different parts as long as the parts can fit within the required size limitations.

    They are n Batch type wash stations n In-line type wash stations 6. Batch wash stations are generally used in low-to mid-volume applications to provide a clean work piece for downstream inspection, assembly or further processing. In an in-line washer, workpieces are loaded at one end of a system, the work pieces are cleaned as they pass through the machine, and removed at the opposite end.

    Separate roller conveyors can be added at the load-unload sections for interfacing. Multiple stages can be added for rinsing, rust prevention, or part blow-dry. Selection of either a batch or In-line wash stations is a function of: For this Batch or In-line wash stations requires spray nozzle, which is to be properly sized, located and directed to clean exterior and interior areas of workpiece. In batch or in-line wash stations an adequate volume and pressure are required for complete flushing of chips from the workpiece fixture and pallet.

    These high-pressure wash stations operate at a 28bar or even more. This high pressure is capable of sharing of encrusted dirt and grease, resulting in a well-cleaned workpiece. Some heavy-duty batch wash stations are capable of automatically locking the pallet assembly to an internal machine circular rail carriage and rotating the entire assembly around the rail during the cleaning and blow-dry cycle.

    This allows better access to recessed areas, improved drainage and increased blow-dry coverage. This reduces drying time of the washed workpiece by blowing off the excess coolant or wash solution, prevents spillover to other machines and other areas of the cell, and helps keep the area clean and neat. Some machines use convector heated air blow-off generated by gas, steam, or electricity in order to speed up the blow- off and part drying cycle and to remove moisture.

    In-line wash stations generally have their own individual and cleaning solution storage tanks equipped for chip recovery and coolant or cleaning solution recirculation, where as in batch wash station the chip and coolant flow directly into the flume system trough to be circulated back to the central coolant storage tank. A sludge conveyor can be used on any type of wash station to handle any volume of dirt, chips. A sludge conveyor basically carries the waste material up to a slope to be deposited in a sludge container for disposal, while the liquid drains back into the central storage tank.

    Wash stations, like the other equipment in a FMS, receive instructions for the host computer or cell controller to their individual programmable controller. These instructions consists of signals primarily to: A typical batch wash stations operational scenario in an FMS would be: Among these key factors is the method for removal of burrs, chips, dirt, grease, tapping compound, and coolant from parts, fixtures and pallets.

    It is important to consider deburring and wash stations processes in an automated cell or system because they can: Deburring and Wash Stations 51 n Provide a cleaner and safer work environment. Of the two processes, cleaning and deburring, cleaning is more flexible and generally easier to add to a cell or system than deburring. Depending on part characteristics and other factors, it may not always be cheaper.

    Deburring has limited flexibility of operation, as we have already seen. Different types of deburring may be required for different parts of similar work-pieces. If work piece requirements change, the method and type of deburring may have to change. Wash stations, on the other hand, can accommodate a variety of different parts, as long as the parts can fit within the required size limitations. And batch wash stations must be able to accommodate the height and weight of tombstone fixtures.

    Consequently, how large a part and tombstone fixture can be accommodated by a particular wash station is an important factor to be considered in downloading. The problem with traditional measurement techniques is that each measured feature may require individual inspection instruments and individual setups, as well as allowing for increased human error.

    A coordinate measuring machine CMM can fill a valuable role in precision measuring because a surface plate, height gage and indicator inspection procedure are combined to provide a fast, accurate and more convenient alternative to the conventional methods for measuring complex parts. It seems that CMMs offer the answer to all our dimensional measurement problems, but is that really true? Will we get precisely the same results as the traditional methods?

    Measurement with a CMM is a complex process that requires the right training and interruption of data collected. Coordinate measuring machine is an electromechanical system designed to perform coordinate metrology. Coordinate metrology is concerned with the measurement of the actual shape and dimensions of an object and comparing these with the desired shape and dimensions, as specified by the part drawing.

    CMM evaluates the location, orientation, dimensions, and geometry of the part or object. A CMM consists of a contact probe that can be positioned in 3-D space relative to the surfaces of a work part.

    The x, y and z coordinates of the probe can be accurately and precisely recorded to obtain dimensional data concerning the part geometry See the Fig. Probe 2. Mechanical structure 7. The tip of probe is usually a ruby ball, which is used to make contact with the part surface during measurement. Ruby ball is usually made of corundum aluminum oxide , whose properties are high hardness for wear resistance and low density for minimum inertia.

    Probes can have either a single tip or multiple tips. Most probes today are touch-trigger probes, which actuate when the probe makes contact with the part surface. When contact is made between the probe and part surface, the coordinate positions of the probe are accurately measured by displacement transducers associated with each of the three linear axes and recorded by the CMM controller.

    Nearly all CMMs have a mechanical configuration that fits into one of the following six types: The quill can also be moved along the length of the arm to achieve y-axis motion, and the arm can be moved relative to the worktable to achieve x-axis motion. The advantages of this construction are: This provides a more rigid structure than cantilever design.

    One of the problems encountered with the moving bridge is yawing walking in which two legs of the bridge move at slightly different speeds resulting in twisting of bridge. This can be reduced by installing dual drives and position feedback controls for both legs. This bridge eliminates the yawing effect, hence increasing rigidity and accuracy. The arm moves vertically and in and out to achieve y-axis and z-axis motions. Large horizontal machines are suitable for measurement of automobile bodies.

    The probe quill moves relative to the horizontal arm extending between the two rails of the gantry.

    The x-axis and y-axis motions are achieved by moving the worktable, while the probe quill is moved vertically to achieve z-axis motion.

    Both types have various manufacturers and range in size from small tabletop models to the very large and expensive floor-mounted kind. CMMs are available with various computer peripherals and offer a variety of improved software packages, making systems integration of this equipment more practical.

    The measuring table and all the guide ways for example are constructed of high quality granite. Increased use of ceramics is also gaining wide acceptance.

    Floor preparation of coordinate measuring machines is also very important. Solid reinforced concrete foundations are required for vibration dampening. Sometimes CMMs require environmental control. Measured dimensions can only be as accurate and reliable as the stability of their surrounding environment. Axes movements in x, y and z are similar to other vertical and horizontal CNC equipment.

    During the automated inspection process, part dimensions are recorded with the help of probe. The CMM compares the result measurement with the previously input manufacturing tolerances allowed for each dimension and conveys this information to either the host or CMM computer. The CMM computer plays an important role in operation of coordinate measuring machine. In general its primary functions include: The docking procedure at the inspection station is controlled and monitored by a PLC Programmable logic controller.

    The parts to be inspected require preprogrammed inspection programs for each different wok piece. These reside at the host computer level in an FMS. Inspection programs are downloaded in demand to the CMM computer.

    Pallet and part identification are verified and the proper CMM inspection programs are automatically downloaded to the CMM computer. Inspection data from the CMM are automatically compared with pre-established tolerance bands in the CMM part programs. Inspection includes diameter, hole depth, flatness and depths of machined area. If a single work piece is rejected by a CMM, that pallet is automatically routed to material review station.

    If the part is rejected second time, the rejection is recorded in the associated work piece history file on the host computer and the pallet continues its predetermined routing. Deviations can be plotted to provide both graphical SPC and analytical inspection results with the appropriate quality and statistical process control software.

    Many inspectors performing repetitive manual inspection operations. If the inspection function represents a significant labor cost to the plant, then automating the inspection procedures will reduce labor cost. Post-process inspection. CMMs are applicable only to inspection operations performed after the manufacturing process. Measurement of geometric features requiring multiple contact points.

    Geometric features like angle between planes, flatness, etc. Multiple inspection setups are required if parts are manually inspected. Manual inspections are generally performed on surface plates using gage blocks, height gages, and similar devices and a different setup is often required for each measurement. The same group of measurements on the part can usually be accomplished in one setup on a CMM. Complex part geometry. If many measurements are to be made on a complex part, and many contact locations are required, then the cycle time of a DCC Direct Computer Control CMM will be significantly less than the corresponding time for a manual procedure.

    High variety of parts to be inspected. Repeat orders. Using a Direct Computer Control CMM, once the part program has been prepared for the first part, subsequent parts from repeat orders can be inspected.

    Reduced inspection cycle time: Because of the automated techniques included in the operation of a CMM, Inspection procedures are speeded and labor productivity improved. A CMM is a general—purpose machine that can be used to inspect a variety of part configurations with minimum changeover times.

    Reduced operator errors: Automating the inspecting process has an obvious effect of reducing human errors in measurements and setups. Greater inherent accuracy and precision: A CMM is inherently more accurate and precise than the manual surface plate methods that are traditionally used for inspection. Avoidance of multiple setups: Traditional inspection techniques often require multiple setups to measure multiple part features and dimensions.

    In general, all measurements can be made in a single setup on a CMM, thereby increasing throughput and measurement accuracy.

    Unlike traditional robots, AGVs are not manipulators, they are driverless vehicles that are programmed to follow a guide path. In offices they may be used to deliver and pick up the mail. They are even used to transport patrons around in airports. One of the first AGVs was a towing vehicle that pulled a series of trailers between two points. AGV systems did not catch on at that time; however, they were not well received by unions and were never allowed to perform to their full potential.

    The market has now grown to include the United States. The main benefit to AGVs is that they reduce labor costs.

    But in material handling facilities there is another benefit. Material handling has always been dangerous. Obstacle detection is therefore a key to allowing AGVs to interact with personnel safely while optimizing vehicle speeds. AGV technology has been moving forward. There have been advances in navigation systems. Until about10 years ago most AGVs followed electromagnetic wires buried in the floor. Then laser- guided systems came into the market.

    These navigation systems allowed the AGV to determine its position in the plant based on the location of reflectors within the area. The future may be the in- plant equivalent of a global positioning system. Obstacle detection systems, has largely consisted of mechanical bumpers, giant E-stops that stop the AGV if it contacts a person or obstacle.

    Without computer software systems and communications networks, only the simplest AGV functions can be performed. An on-board camera focuses and guides the AGV while performing. These can be manually driven as well as used automatically, and have the ability to lift loads to many levels. Magnets mounted beneath the floor are detected by the on-board magnetic sensing device and combine with the first two readings to give an accurate positional location.

    Distance is measured by use of wheel odometers, which establish stop locations for the AGV along the course. These can follow a basic loop or a more complicated path. The stronger the field between the buried wire and antennae, the higher the voltage induced to the coils. Roller or chain conveyor, fixed load table, lifting load table or arms, telescopic fork, etc. Again, a modular approach can be taken in all communication and reporting systems to aid in diagnostics and reduce the overall downtime.

    And the Layout Development Kit speeds up the work of developing a new system, especially in Laser Guidance scenarios. Two-step detection of non contact collision prevention sensor Fig. Load Including the conveyor weight Capacity If a conveyor is added, the permissible load capacity is decreased by its weight. Marking tape counting up system No. PLC function Input: Ladder diagram language, Programming with the GCP option , max. The acceleration, deceleration and other effects that influence the speed are ignored.

    The delivery cycle time can be used to determine the rate of deliveries per vehicle and number of vehicles required. The hourly rate of deliveries per vehicle is 60 minutes divided by the delivery cycle time Tv, with adjusting for any time losses during the hour. The possible time losses include availability, traffic congestion and efficiency of manual drivers. Also determine the handling system efficiency. The system must be capable of making 40 deliveries per hour. The following are the data of performance characteristics of the system: Also determine the handling system efficiency?

    The system must make a total of 75 deliveries per hour.

    The load and unload times are both 0. Determine the average total time per delivery, the handling system efficiency and the resulting average number of deliveries per hour for a vehicle. How many vehicles are needed to satisfy the indicated deliveries per hour?

    The system must be capable of making 60 deliveries per hour. Mini loads may be used in traditional stockroom applications but are also well suited as buffers to support manufacturing processes and shipping systems. This technology finds itself at the heart of systems varying widely in application from the food industry to the manufacturing floor. In addition to a complete line of conveyors, transfers and ergonomic devices, Industrial Kinetics, Inc.

    Our innovative equipment can interface with carousels, live or static rack installations, and custom configured work cells. Industrial Kinetics, Inc. The transaction cycle involves retrieval of load out of storage or delivery of a load in to the storage or both of the activities in a single cycle. The two types of transaction cycles are: Single command cycle: It involves either retrieving a load from the storage or entering a load into the storage but not both in a single cycle.

    Dual command cycle: It involves both entering a load into storage and retrieval of the load from storage in the same cycle. The individual bins are hung on carriers that revolve around the carousel track. Let us consider a retrieval cycle and the storage transaction is performed under the same assumption of random storage would be equivalent to a retrieval transaction.

    The average distance that the carousel has to travel to move randomly located bin to the unload station at the end of the carousel depends on whether the carousel revolves in only one or both directions. The length of storage aisle is m and its height is 50 m. Determine the single and dual command cycle times. Therefore single command transaction cycle time is given by: Example 8.

    There are carriers around the carousel and each carrier has 5 bins suspended from it. For a single direction carousel and a bidirectional carousel, compare how long it take it takes to retrieve 20 parts from the carrier if each part is in different storage bin and random storage is used in the carousel. Also determine the spacing between carriers and carousel. The handling time associated with retrieval is 20 seconds. Problems 8. The P and D time is 0.

    Determine the average single command and dual command transaction times for the storage system. Compute the average time to retrieve a part from the system: Each carousel has a track that is 60 m long and 3. The P and D handling time is 0. Determine the throughput rate of the storage system if the storage transaction and retrieval transactions are 4 equally divided during the shift.

    Assume bidirectional travel of the carousel. Computer integrated manufacturing utilizes CAD, CAM, CNC and robots to create work cells that perform a series of operations from the design of the part to its complete creation without the use of human labor.

    Robots are also well suited for doing heavy, dangerous and repetitive tasks. The first industrial robot, created by a company called Unimat, was downloadd by Ford Motor Company in An inventor by the name of George C. Devol conceived the idea and with the help of Joe Engelberger, a manufacturing executive, the robot became a reality. Since the robot replaced human workers, organized labor resisted the move by major companies to incorporate these devices on the assembly lines.

    In addition, the cost of early produced robots was in the hundreds of thousand of dollars so only the largest manufacturing concerns could justify their use. Decreasing productivity and increasing labor costs eventually forced companies to use robots. With the demand for robots increasing, more companies began to build newer and better robots and the cost of robots dropped rapidly.

    The number one user of robots in the U. Welding, loading, unloading, machining, moving and painting are the principal tasks of existing robots with gluing, cleaning, checking, inspecting, and packaging as the newer jobs facing robots. In the near future, the fast food industry is hoping to use robots to prepare, cook and serve food items as well as dispense beverages automatically in response to customer selections.

    Robots are useful in industry for a variety of reasons. Installing robots is often a way business owners can be more competitive, because robots can do some things more efficiently than people. Robots never get sick or need to rest, so they can work 24 hours a day, 7 days a week. When the task required would be dangerous for a person, they can be do the work instead. The mechanical structure links, base, etc. This requires a great deal of mass to provide enough structural rigidity to ensure minimum accuracy under varied payloads.

    The motors, cylinders, etc. This might also include mechanisms for a transmission, locking, etc. Control Computer: This computer interfaces with the user, and in turn controls the robot joints. Automated Material Movement and Storage System 79 4. The tooling is provided be the user, and is designed for specific tasks. Teach pendant: One popular method for programming the robot.

    This is a small hand held device that can direct motion of the robot, record points in motion sequences, and begin replay of sequences. More advance pendants include more functionality. The major classes of robots include, n Arms fixed in place, but can reach and manipulate parts and tools n Mobile these robots are free to move 8. Prismatic slider joints in which the link is supported on a linear slider bearing, and linearly actuated by ball screws and motors or cylinders.

    Positioning is done in the workspace with prismatic joints. This configuration is well used when a large workspace must be covered or when consistent accuracy is expected from the robot. The robot has a revolute motion about a base, a prismatic joint for height and a prismatic joint for radius. This robot is well suited to round workspaces. Two revolute joints and one prismatic joint allow the robot to point in many directions, and then reach out some radial distance.

    The robot uses 3 revolute joints to position the robot. Generally the work volume is spherical. This robot most resembles the human arm, with a waist, shoulder, elbow, and wrist. This robot conforms to cylindrical coordinates, but the radius and rotation is obtained by a two planar links with revolute joints. The earliest applications were in materials handling, spot welding, and spray painting. Robots were initially applied to jobs that were hot, heavy, and hazardous such as die-casting, forging, and spot welding.

    The repeatability, uniformity quality, and speed of robotic welding are unmatched. The two basic types of welding are spot welding and arc welding, although laser welding is done. Some environmental requirements should be considered for a successful operation. The automotive industry is a major user of robotic spot welders.

    The other major welding task performed by robots is arc or seam welding. In this application two adjacent parts are joined together by fusing them, thereby creating a seam. Automated Material Movement and Storage System 83 The spray painting applications seems to epitomize the proper applications of robotics, relieving the human operator from a hazardous, albeit skillful job, while at the same time increasing work quality, uniformity, and cutting costs.

    In addition, their high level of repeatability has allowed the development of some new technologies in electronic assembly. The newspaper industry has been particularly hard hit by increased labor costs.

    Part of the solution to this problem was to use robots like Cincinnati Milacron Robot being used to palletize advertising inserts for a newspaper. Many companies in the United States and Canada have been forced to close in such areas as die casting Fig.

    The introduction of robotics into this process has allowed the same companies to remain viable. This requires that personnel as well as robots not introduce dirt, dust, or oil into the area. Since robots do not breath, sneeze, or have dandruff, they are especially suited to the clean room environment demanded by the semiconductor industry.

    This includes not only having and maintaining the required number of cutting tools to process the required parts through the FMS but also managing and coordinating other elements such as n Replacement of tools. Getting Control of cutting tools: Controlling the cutting tools involves good tooling policies, cost-effective part programming strategies on the machine, and sound tool-related practices in tool rooms, manufacturing and other off-line operations.

    The following items should be considered as cost-effective, optimizing tactics to begin to augment and enhance the full impact of FMS productivity effectiveness. Such out of control activities can resort to unnecessary and costly extra perishable tool downloads. The main problems caused by tool capacity constraints and a lack of tool management are: Insufficient redundant tool backup at the machine during tool breakage and tool wear conditions.

    Insufficient use of present tools and excess tool inventory. Conflicting priorities with other areas outside the FMS over tool availability and reconditioning. A limited number of workpieces being available to process due to insufficient tool, matrix capacity. Under-utilized machines and low production rates caused by too many tools and extensive tool changing. Generally, tool management is getting the right tool to the right place at the right time.

    5 What is a flexible manufacturing system and under what set of circumstances

    Having an acceptable tool management system to fulfill the tooling requirements of an FMS means adequately addressing the following four areas: Tool room service is a necessary support function dealing principally with preparing, servicing, organizing and controlling the vast array of perishable tools, inserts, tool holders and tool components. The principal elements of tool room service are: Cutting Tools and Tool Management 87 9. This includes transporting the tools to and from the machine tool requiring those tools, and loading and unloading the tool magazines once the tool arrive at the machines.

    If the demand for tools based on the variety of part mix is high enough, complete automation of the tool delivery and distribution function may be necessary. Tool allocation is essentially assigning and controlling the total number of tools required for each machine to process the previously defined FMS part spectrum. It is based on specific part process plans, machine programs and machining methodology along with the varying part mix and volumes that could be running through the system at any given time.

    Controlling the tool data flow relative to the allocated tools requires that the MCU Machine control unit would assume tool data transfer from the present area as tools are automatically gauged, identified and entered into the FMS tool system data base.

    This involves electromechanical and optical sensing and detection of worn and broken tools along with absence of tools or misplacements. Each tool is offset to a contact and non-contact sensor. Each time it is used in order to validate tool presence, correctness and condition. Replacements should be available for the broken tools. Each has its advantages and disadvantages as well as particular application for an FMS. The tool strategies employed in FMS are: The mass exchange strategy is logical and attractive for FMS applications only where high volume and low part variety workpiece exists.

    Common tooling among the fixed production requirements is recognized, identified and shared among the various parts to be manufactured in the fixed production period. After fulfilling part requirements within the fixed production period, a new set of tools for the next production is loaded and common tooling is again identified.

    The tool strategy requires computer software to implement due to merging of tool lists and matching requirements to identify the common tooling. Both consider the workpiece to be manufactured within the fixed production period and tool matrix capacity available to support it. As parts are completed, many tools used to manufacture those parts become available for removal from the tool matrix.

    Removing the tools frees tool points in the tool matrix and permits other tools needed for new arriving parts to be loaded. Tool migration exchanges must be done in an effort to minimize spindle interruption is of primary importance.

    Consequently, tools completing their manufacture service are removed from the matrix at the tool matrix, while needed new tools are inserted in available tool pockets. Tool delivery is accomplished through various means such as AGV.

    The Strategy requires sophisticated computer software and decision logic in order to determine the removal of tools, adding of this tool.

    The reality of manufacturing operation forces consideration of production schedule changes, machine breakdowns, tooling and material unavailability, flexibility among processing equipment becomes high priority. Thus, the assigned tool strategy can address the need for increased flexibility among a set or group machine tools.

    This strategy identifies the most used tools for the production requirements and part mix and assigns permanent residence to those tools in each machine tool matrix for the full production run. However, time consuming and most importantly open to human error as touch sensitivity is highly subjective. Therefore, many presetting machines are based on touch-readout tool gauges and optical projection systems that magnify the tool point.

    Sophisticated identification systems are available and are being used in FMS and other factory automation applications but have much broader and long-range potential. Automated identification systems are important because they are reliable, save time and reduce human error. The most common of these identification systems are: The control unit remembers the pocket where each unique coded tool was placed. Bar codes are made up of binary digits arranged so that the bars and spaces in different configurations represent numbers, letters and other symbols.

    Scanners that read bar codes contain a source of intense light produced by a laser or light emitting diode and aimed at the pattern of black bars and spaces of varying widths.

    The black bars absorb the light and the spaces reflect it back into the scanner. The scanner then transforms the patterns of light and dark into electrical impulses that are measured by a decoder and translated into binary digits for transmission to the computer. Bar codes are made up of binary digits arranged so that the bar and spaces in different configurations represent number. Although the imaging process itself is more complex than that of bar code scanning, the technology has potential for a large number of applications, many of which are FMS related.

    Application would include character reading, sorting by shape of markings and locating defective parts or pallets. Radio frequency identification offers solution to application problems in industrial automation and matter handling where there is no line of direct sight between the scanner and the identification plate or tag.

    When the scanner recognizes a particular pattern, the data are converted to electronic impulses for transmission to the computer. This system uses a non-contact read-only head that can be attached to tool changers, presetting fixtures or tool grippers. Reading can occur at a distance of up to 0. With an allowable 0.

    The microchip can also be programmed offline with the tool identification and other dimensional data. Cutting Tools and Tool Management 91 9. The tool-preset operator assigns an identification number to the entire physical collection of tools.

    This identification associates the physical collection of cutting tools with the data that are collected on each of the tools. If an electronic tool gauge is being used, the gauged values of tool length and diameter are automatically read from the gauge and transferred and stored in a tool collection file on the FMS computer. Tool life refers to the time during which a cutting tool produces acceptable parts in a machining operation.

    A cutting tool is considered to have reached the extent of its useful life when any of the following occur. Tool monitoring therefore becomes a comparison of how much useful life should exist on a given tool measured against the actual cutting time of the tool.

    When the actual cutting tool time as tracked by the host computer in FMS application expires, the FMS can be set up to perform one of the following actions: The delivery cycle time can be used to determine the rate of deliveries per vehicle and number of vehicles required. The hourly rate of deliveries per vehicle is 60 minutes divided by the delivery cycle time Tv, with adjusting for any time losses during the hour.

    The possible time losses include availability, traffic congestion and efficiency of manual drivers. Also determine the handling system efficiency. The system must be capable of making 40 deliveries per hour. The following are the data of performance characteristics of the system: Also determine the handling system efficiency? The system must make a total of 75 deliveries per hour. The load and unload times are both 0. Determine the average total time per delivery, the handling system efficiency and the resulting average number of deliveries per hour for a vehicle.

    How many vehicles are needed to satisfy the indicated deliveries per hour? The system must be capable of making 60 deliveries per hour. Mini loads may be used in traditional stockroom applications but are also well suited as buffers to support manufacturing processes and shipping systems.

    This technology finds itself at the heart of systems varying widely in application from the food industry to the manufacturing floor.

    In addition to a complete line of conveyors, transfers and ergonomic devices, Industrial Kinetics, Inc. Our innovative equipment can interface with carousels, live or static rack installations, and custom configured work cells.

    Industrial Kinetics, Inc. The transaction cycle involves retrieval of load out of storage or delivery of a load in to the storage or both of the activities in a single cycle.

    The two types of transaction cycles are: Single command cycle: It involves either retrieving a load from the storage or entering a load into the storage but not both in a single cycle. Dual command cycle: It involves both entering a load into storage and retrieval of the load from storage in the same cycle. The individual bins are hung on carriers that revolve around the carousel track.

    Let us consider a retrieval cycle and the storage transaction is performed under the same assumption of random storage would be equivalent to a retrieval transaction. The average distance that the carousel has to travel to move randomly located bin to the unload station at the end of the carousel depends on whether the carousel revolves in only one or both directions.

    The length of storage aisle is m and its height is 50 m. Determine the single and dual command cycle times. Therefore single command transaction cycle time is given by: Example 8.

    There are carriers around the carousel and each carrier has 5 bins suspended from it. For a single direction carousel and a bidirectional carousel, compare how long it take it takes to retrieve 20 parts from the carrier if each part is in different storage bin and random storage is used in the carousel. Also determine the spacing between carriers and carousel. The handling time associated with retrieval is 20 seconds.

    Problems 8. The P and D time is 0. Determine the average single command and dual command transaction times for the storage system. Compute the average time to retrieve a part from the system: Each carousel has a track that is 60 m long and 3. The P and D handling time is 0. Determine the throughput rate of the storage system if the storage transaction and retrieval transactions are 4 equally divided during the shift.

    Assume bidirectional travel of the carousel. Computer integrated manufacturing utilizes CAD, CAM, CNC and robots to create work cells that perform a series of operations from the design of the part to its complete creation without the use of human labor.

    Robots are also well suited for doing heavy, dangerous and repetitive tasks. The first industrial robot, created by a company called Unimat, was downloadd by Ford Motor Company in An inventor by the name of George C. Devol conceived the idea and with the help of Joe Engelberger, a manufacturing executive, the robot became a reality. Since the robot replaced human workers, organized labor resisted the move by major companies to incorporate these devices on the assembly lines.

    In addition, the cost of early produced robots was in the hundreds of thousand of dollars so only the largest manufacturing concerns could justify their use. Decreasing productivity and increasing labor costs eventually forced companies to use robots.

    With the demand for robots increasing, more companies began to build newer and better robots and the cost of robots dropped rapidly. The number one user of robots in the U. Welding, loading, unloading, machining, moving and painting are the principal tasks of existing robots with gluing, cleaning, checking, inspecting, and packaging as the newer jobs facing robots. In the near future, the fast food industry is hoping to use robots to prepare, cook and serve food items as well as dispense beverages automatically in response to customer selections.

    Robots are useful in industry for a variety of reasons. Installing robots is often a way business owners can be more competitive, because robots can do some things more efficiently than people. Robots never get sick or need to rest, so they can work 24 hours a day, 7 days a week. When the task required would be dangerous for a person, they can be do the work instead.

    The mechanical structure links, base, etc. This requires a great deal of mass to provide enough structural rigidity to ensure minimum accuracy under varied payloads. The motors, cylinders, etc. This might also include mechanisms for a transmission, locking, etc. Control Computer: This computer interfaces with the user, and in turn controls the robot joints. Automated Material Movement and Storage System 79 4. The tooling is provided be the user, and is designed for specific tasks.

    Teach pendant: One popular method for programming the robot. This is a small hand held device that can direct motion of the robot, record points in motion sequences, and begin replay of sequences. More advance pendants include more functionality. The major classes of robots include, n Arms fixed in place, but can reach and manipulate parts and tools n Mobile these robots are free to move 8. Prismatic slider joints in which the link is supported on a linear slider bearing, and linearly actuated by ball screws and motors or cylinders.

    Positioning is done in the workspace with prismatic joints. This configuration is well used when a large workspace must be covered or when consistent accuracy is expected from the robot. The robot has a revolute motion about a base, a prismatic joint for height and a prismatic joint for radius. This robot is well suited to round workspaces. Two revolute joints and one prismatic joint allow the robot to point in many directions, and then reach out some radial distance.

    The robot uses 3 revolute joints to position the robot. Generally the work volume is spherical. This robot most resembles the human arm, with a waist, shoulder, elbow, and wrist. This robot conforms to cylindrical coordinates, but the radius and rotation is obtained by a two planar links with revolute joints. The earliest applications were in materials handling, spot welding, and spray painting.

    Robots were initially applied to jobs that were hot, heavy, and hazardous such as die-casting, forging, and spot welding. The repeatability, uniformity quality, and speed of robotic welding are unmatched.

    The two basic types of welding are spot welding and arc welding, although laser welding is done. Some environmental requirements should be considered for a successful operation. The automotive industry is a major user of robotic spot welders. The other major welding task performed by robots is arc or seam welding. In this application two adjacent parts are joined together by fusing them, thereby creating a seam.

    Automated Material Movement and Storage System 83 The spray painting applications seems to epitomize the proper applications of robotics, relieving the human operator from a hazardous, albeit skillful job, while at the same time increasing work quality, uniformity, and cutting costs. In addition, their high level of repeatability has allowed the development of some new technologies in electronic assembly.

    The newspaper industry has been particularly hard hit by increased labor costs. Part of the solution to this problem was to use robots like Cincinnati Milacron Robot being used to palletize advertising inserts for a newspaper. Many companies in the United States and Canada have been forced to close in such areas as die casting Fig. The introduction of robotics into this process has allowed the same companies to remain viable.

    This requires that personnel as well as robots not introduce dirt, dust, or oil into the area. Since robots do not breath, sneeze, or have dandruff, they are especially suited to the clean room environment demanded by the semiconductor industry.

    This includes not only having and maintaining the required number of cutting tools to process the required parts through the FMS but also managing and coordinating other elements such as n Replacement of tools.

    Getting Control of cutting tools: Controlling the cutting tools involves good tooling policies, cost-effective part programming strategies on the machine, and sound tool-related practices in tool rooms, manufacturing and other off-line operations. The following items should be considered as cost-effective, optimizing tactics to begin to augment and enhance the full impact of FMS productivity effectiveness.

    Such out of control activities can resort to unnecessary and costly extra perishable tool downloads. The main problems caused by tool capacity constraints and a lack of tool management are: Insufficient redundant tool backup at the machine during tool breakage and tool wear conditions. Insufficient use of present tools and excess tool inventory.

    Conflicting priorities with other areas outside the FMS over tool availability and reconditioning. A limited number of workpieces being available to process due to insufficient tool, matrix capacity. Under-utilized machines and low production rates caused by too many tools and extensive tool changing. Generally, tool management is getting the right tool to the right place at the right time. Having an acceptable tool management system to fulfill the tooling requirements of an FMS means adequately addressing the following four areas: Tool room service is a necessary support function dealing principally with preparing, servicing, organizing and controlling the vast array of perishable tools, inserts, tool holders and tool components.

    The principal elements of tool room service are: Cutting Tools and Tool Management 87 9. This includes transporting the tools to and from the machine tool requiring those tools, and loading and unloading the tool magazines once the tool arrive at the machines. If the demand for tools based on the variety of part mix is high enough, complete automation of the tool delivery and distribution function may be necessary.

    Tool allocation is essentially assigning and controlling the total number of tools required for each machine to process the previously defined FMS part spectrum. It is based on specific part process plans, machine programs and machining methodology along with the varying part mix and volumes that could be running through the system at any given time. Controlling the tool data flow relative to the allocated tools requires that the MCU Machine control unit would assume tool data transfer from the present area as tools are automatically gauged, identified and entered into the FMS tool system data base.

    This involves electromechanical and optical sensing and detection of worn and broken tools along with absence of tools or misplacements. Each tool is offset to a contact and non-contact sensor.

    Each time it is used in order to validate tool presence, correctness and condition. Replacements should be available for the broken tools. Each has its advantages and disadvantages as well as particular application for an FMS. The tool strategies employed in FMS are: The mass exchange strategy is logical and attractive for FMS applications only where high volume and low part variety workpiece exists.

    Common tooling among the fixed production requirements is recognized, identified and shared among the various parts to be manufactured in the fixed production period. After fulfilling part requirements within the fixed production period, a new set of tools for the next production is loaded and common tooling is again identified. The tool strategy requires computer software to implement due to merging of tool lists and matching requirements to identify the common tooling. Both consider the workpiece to be manufactured within the fixed production period and tool matrix capacity available to support it.

    As parts are completed, many tools used to manufacture those parts become available for removal from the tool matrix. Removing the tools frees tool points in the tool matrix and permits other tools needed for new arriving parts to be loaded. Tool migration exchanges must be done in an effort to minimize spindle interruption is of primary importance. Consequently, tools completing their manufacture service are removed from the matrix at the tool matrix, while needed new tools are inserted in available tool pockets.

    Tool delivery is accomplished through various means such as AGV.

    Tool addition strategies for flexible manufacturing systems

    The Strategy requires sophisticated computer software and decision logic in order to determine the removal of tools, adding of this tool. The reality of manufacturing operation forces consideration of production schedule changes, machine breakdowns, tooling and material unavailability, flexibility among processing equipment becomes high priority. Thus, the assigned tool strategy can address the need for increased flexibility among a set or group machine tools.

    This strategy identifies the most used tools for the production requirements and part mix and assigns permanent residence to those tools in each machine tool matrix for the full production run. However, time consuming and most importantly open to human error as touch sensitivity is highly subjective. Therefore, many presetting machines are based on touch-readout tool gauges and optical projection systems that magnify the tool point.

    Sophisticated identification systems are available and are being used in FMS and other factory automation applications but have much broader and long-range potential. Automated identification systems are important because they are reliable, save time and reduce human error. The most common of these identification systems are: The control unit remembers the pocket where each unique coded tool was placed. Bar codes are made up of binary digits arranged so that the bars and spaces in different configurations represent numbers, letters and other symbols.

    Scanners that read bar codes contain a source of intense light produced by a laser or light emitting diode and aimed at the pattern of black bars and spaces of varying widths. The black bars absorb the light and the spaces reflect it back into the scanner. The scanner then transforms the patterns of light and dark into electrical impulses that are measured by a decoder and translated into binary digits for transmission to the computer.

    Bar codes are made up of binary digits arranged so that the bar and spaces in different configurations represent number. Although the imaging process itself is more complex than that of bar code scanning, the technology has potential for a large number of applications, many of which are FMS related. Application would include character reading, sorting by shape of markings and locating defective parts or pallets.

    Radio frequency identification offers solution to application problems in industrial automation and matter handling where there is no line of direct sight between the scanner and the identification plate or tag. When the scanner recognizes a particular pattern, the data are converted to electronic impulses for transmission to the computer.

    This system uses a non-contact read-only head that can be attached to tool changers, presetting fixtures or tool grippers. Reading can occur at a distance of up to 0. With an allowable 0. The microchip can also be programmed offline with the tool identification and other dimensional data. Cutting Tools and Tool Management 91 9. The tool-preset operator assigns an identification number to the entire physical collection of tools. This identification associates the physical collection of cutting tools with the data that are collected on each of the tools.

    If an electronic tool gauge is being used, the gauged values of tool length and diameter are automatically read from the gauge and transferred and stored in a tool collection file on the FMS computer. Tool life refers to the time during which a cutting tool produces acceptable parts in a machining operation. A cutting tool is considered to have reached the extent of its useful life when any of the following occur.

    Tool monitoring therefore becomes a comparison of how much useful life should exist on a given tool measured against the actual cutting time of the tool. When the actual cutting tool time as tracked by the host computer in FMS application expires, the FMS can be set up to perform one of the following actions: Tool monitoring measures normal tool wear against a predetermined standard stored on the FMS host computer and excludes recognition and detection of major tool failures or breakage.

    The gathering and compiling of machinability information for a tool life data-box should be the responsibility of each user. In a random user FMS, it is possible to run parts consisting of different material types.

    Care should be exercised when setting up the tool life data-box to categorize tools by part material type. Tool life monitoring places heavy emphasis on copies of redundant tools, related components and holders must be available to provide for a constantly changing mix of parts to machine. An accelerometer was mounted on the cutting tool holder attached to the turret, as shown in Fig. The vibration signals were first amplified using a charge amplifier and low-pass filter with cut-off frequency of 6 kHz, and then sampled at kHz using a bit data acquisition card.

    Every data set was 0. When the cutting edge develops an average flank wear height of at least 0. There are many reasons for this. By monitoring tools, you can get more parts per tool. Tool costs are lowered because you are using the tool properly and sharpening it only when needed. This will also reduce machine downtime, labor to change out the tools and grinding costs.

    In addition, tool inventory can be reduced. Instead of having many duplicate tools, because you never know when the tool needs changing or will fail, you can develop your inventory around set parameters that a monitoring system offers.

    You can also get faster new part process development. With tool monitoring, labor can be reduced, because fewer tool inspections and changes will be needed. Also, because the tools are being monitored second by second, highly skilled operators can be better used for machine setup and planning jobs.

    Scrap can be significantly reduced because dull tools that produce scrap have been taken out of service before they can cause problems. Catastrophic failures will be reduced or eliminated with appropriate tool changes. If a vendor wants you to try out new tooling, you can monitor that tool and compare it to the old one.

    Also, when a shift change occurs, the second shift would not have to communicate with the first shift to find out what tools need to be changed. A tool monitoring system would provide the information. With control over tooling costs and labor usage, a company can have higher overall efficiency along with improved part quality. Accurate cost estimating both for the part and tooling can also be achieved by using historical reports.

    This all boils down to increased profit for a company and greater overall cost control. A system boundary chosen for modeling the spindle drive involves part of the DC motor and the spindle as shown in Fig. There are several reasons for this choice: The armature current and motor speed can be easily measured.

    That leaves only one unknown, the cutting force that can be estimated from the model and the measurements. Measurement of the high frequency voltage signal from an SCR amplifier can be avoided.

    The motor current is easier to measure than the armature voltage because the inductance and resistance of the armature windings filter much of the high frequency noise. The parameters of the armature windings are excluded from the system.

    This means that the motor resistance, which changes with temperature, does not have to be considered. An Eigen value analysis of the linear model in Fig.

    Thus a first order model is obtained, which includes the dynamic effects induced by the system inertia and the effects of the energy losses in the system due to the bearing friction. Tts is not just the cutting torque applied to workpiece. To calculate the normal cutting force from the estimated total external torque applied to the spindle motor, detailed information about the components of Tts is necessary.

    This can be done through off-line tests. The parameters that do not change during cutting operations can be determined by off-line tests. Coulomb friction without cutting T fs ; total equivalent inertia of the spindle system as seen by the spindle motor J s ; and parameters for the nonlinear friction model.

    This parameter is dependent on temperature and operating conditions. The quantities that can be monitored include power consumption, torque, force, vibration, acoustic emission, tool wear, tool temperature, etc. The eTCM employs multiple sensors to monitor the machining process condition. The monitoring sensors include accelerometer, dynamometer, microphone, and acoustic emission AE sensor. Integration or fusion of data from multiple sensors improves the detection accuracy and provides several advantages over data from a single sensor in tool condition monitoring.

    A Kistler quartz 3-component platform dynamometer was mounted between the workpiece and machining table to measure the cutting forces.

    Two Kistler piezo-accelerometers were used to measure the machine tool vibrations in cutting, one accelerometer was mounted to the spindle quill and the other one was applied to the work-piece fixture. An AE sensor was mounted on the fixture. The outputs of these sensors were conditioned through corresponding signal conditioning accessories such as charge amplifiers or couplers, and then were passed to the data acquisition module.

    The computer can do nothing, however, without the required application software, people, and the necessary communication links to the various workstations. The computer requires proven application software, competent and trained personnel, and backup resources in order for the entire system to perform at acceptable levels. The FMS computer is a tool and functional component like any other element in a flexible manufacturing system. Although it is simply a means by which the FMS application software and initiates system activity, it is, in essence, the heart of an FMS.

    General functions and manufacturing usage: These data groups, although listed as independent pieces of information and designed for convenience of the user, must be able to interface through one from or another and exchange files and records. System Hardware and General Functionality 97 The information resides in one central computer and in one database.

    This is the centralized- decentralized argument of computers and computer control. Each has its advantages and disadvantages. As installation size and complexity increases, reliability and responsiveness decreases.

    In the case of major computer failure, if the entire system breaks down, all plant communication would be lost. However, having large central computers provides more consolidated control of computer charges and expenses, while reducing duplication of new application programming effort within the overall organization. Decentralized computers those handling pockets of applications within an organization gives users more control of their own destiny for improved responsiveness and may be connected to other computers or to a central mainframe for data distribution.

    Centralized control of expenses and computation charges is difficult to obtain due to local or departmental control of the decentralized computers. Table High hardware cost 1. Lower hardware cost 2. High software cost 2. Lower software cost 3. High in-plant wiring and connection costs 3. Lower in-plant wiring and connection costs 4.

    Software complex, time consuming and 4. Software application specific designed for local difficult to change and maintain use, easy to write, modify and maintain. Easy to trace overall operating costs and 5. Harder to track overall operating costs and control expenses control expenses 6. Low computer transaction response time, 6.

    Fast computer response time user controls own priorities assigned and controlled by application environment and assigns own corporate data processing priorities 7. Expandability difficult and hard to justify 7. Expandability easy, less expensive and less cost difficult to justify 8. All plant communications shut down with 8. Only isolated location shut down with computer computer failure computer failure 9. Expensive backup resources required 9. Less expensive backup resources required, spare computer can be available as standby Application program changes is time Application changes easy to make and in control consuming to implement, central data of local users processing must evaluate, prioritize, analyze, and determine system impact The functions of a PLC are to examine the status of an input or set of inputs and based on this status, acute or regulate an output device or devices.

    Input to a PLC may be either discrete or continuous. Discrete PLC inputs typically come from photocells, proximity and limits, push buttons, micro switches and pressure switches. Continuous PLC inputs come from voltmeters, potentiometers, solenoid valves, and motor starters, and in the case of FMS to initiating some activity at the various workstations.

    A PLC is composed of four primary elements: Most PLCs now being offered are microprocessor based and have more logic and control capabilities than the earlier electronic logic circuit models. The CPU scans the status of the various input devices continuously, applies the input signals to the memory control logic, and produces the required output responses needed to activate and control the equipment or workstation entry-exit points. Micro and mini PLCs are usually modern replacements for relay systems.

    Larger units may have the functional capabilities of a small computer and be able to handle computational functions, generate and output reports, and provide high-level communications capabilities. Instructions are input to a PLC in the form of programs, just as for other computers. Four major programming languages are generally used with PLCs. These include ladder diagrams, Boolean mnemonics, functional blocks and English statements. This includes each of the individual workstations for part processing, inspection, cleaning and others.

    Additionally, PLCs are used to control loading unloading and fixture build stations, queuing stations and carrousels, automatic storage and retrieval systems ASRS , and control coolant- chip reclamation systems.

    Signals are passed back and forth between each of the PLCs in the FMS and the host computer in order to activate and verify pallet shipment, movement, registration, and receipts and to initiate activity of other FMS system functions. Cell controllers are generally are factory hardened to exist on the shop floor but are not used to directly control shop equipment. Cell controllers are generally used to control PLCs or PCs, which in turn control a manufacturing cell or a series of machine tools.

    Cell controllers provide computerized supervision and coordination of multiple controllers along with data collection and concentration for the factory floor.

    Cell controllers also provide a distributed database and communication capabilities to higher-level computers, such as the factory host or the inventory control system computer. Cell controllers are generally used for small-scale FMS or cellular systems where the full range of system decision-making capabilities is not required to support diverse part mix and lot size requirements. This would include mid-to higher-volume applications with some part type and mix variety but high cell coordination and data management requirements.

    The primary difference between cell controllers and PLCs is the computer language and knowledge required to program and maintain them. Little computer knowledge is necessary to program PLCs. Cell controllers, on the other hand, require some degree of computer knowledge, along with more operator knowledge and training to use than programmable controllers. Electronic repair personnel, if easily replaced, may stock repair parts for PLCs, in cases or they may be obtained from distributors.

    How quickly a manufacturer can react to cell or system trouble in an important consideration when selecting a cell controller vendor. Communications between various cells, other plant computers, and the factory floor can be either horizontally or vertically integrated. Communication between the islands of automation or manufacturing cells is horizontal integration and should be considered as primary building block of CIM.

    This level of integration may be sufficient if automation is the only goal. This level of communication establishes the foundation for vertical communications. Vertical communications are integrated upward and downward between the plant host computer and office level and the cell and plant floor level. However, it is important to note that, without horizontal communication integration, vertical integration cannot be fully achieved in a CIM network. Many cell controller applications do not require the functionality or the price of larger systems.

    Smaller-scale cell controllers, for example, can be used to automate towards CIM in a logical step by step or phased in approach. Such an approach can hold down the price of distributed cell controller architecture, thereby lowering the overall implementation cost of CIM.

    Selection either of the network or computer, in many cases, may determine the other. Some networks are closer to being standardized and supported by computer vendors than others.

    Networks are generally localized based on the elements that need to be linked together in a given area. Consequently, the acronym LAN Local Area Network is used in many cases to designate the network or data transfer line.

    Local Area Networks LANs fit Local Area Networks may be limited to a room, a building, an automated system, or a series of closely connected systems or buildings.

    Network topology is the road map of the entire network. Although the word topology is basically a misuse of the word topography, it is the geometric layout of the data links and the computers that require linkage.

    Network topology can have many forms, but the two most common are point-to- point and multidrop. Point-to-point topology is a circuit connecting two points or computer nodes without passing through an intermediate point. The primary use is for very simple or sub networks. A multidrop network is a single line that is shared by two or more computer nodes.

    Multidrop networks reduce overall line costs, but increase in the complexity of data transfer in the network, as well as the cost of the line connection. The method of data control and priorities in either a point-to-point or multidrop application is the control topology.

    Star or Radial 2. Ring or Loop 3. Bus The connecting point would be called the slave. This is a simple master-slave relationship.

    This type of network controlled by the net master in a master-slave relationship is shown in the Fig. Centralizing control in one node of the network creates what is generally referred to as a loop network. Sub nodes in a network can only communicate with other sub nodes when permitted by the controlling master node. Ring networks are distributed control. In this case, each node can communicate with every other node without direction from a controlling master node.

    This method is more complex more than loop arrangements, but in either case Ring or Loop data may be passed from node to node round the ring. Each node must have an active repeater to transmit the data to the next node. Ring or loop network is shown in the Fig. A bus network is significantly different from the other arrangements in that data may be sent to all nodes at the same time, as opposed to passing data from ode to node around a ring.

    This is shown in the Fig. The efficiency of a bus network in an FMS or any other automation application depends on the following factors: Polling is a technique in which each nodes access to the network is determined by the master node. If a centralized polling scheme is used, the central node will query each sub node and ask if it has access to the network. Each nodes frequency of access depends on how much other data traffic needs to be passed between the other nodes in the network and the total number of nodes on the network.

    Some polling schemes can assign priority to selected nodes by querying them more often. Figure A common form of distributed polling is called token passing. Token passing is generally associated with ring or loop networks and functions by passing a packet of bits called token around the loop until it reaches am node that requires access to the network. That particular node will grab and hold the token while it sends its data.

    Once a message is on the ring, it is passed from node to node until received by the destination node. Messages usually circulate back to the sending node to control receipt. When the sending node has completed its transmission, it puts the token back in circulation. The major elements consist of a variety of processing, quality assurance, computer hardware, and system support equipments, all of which are visible and tangible.

    Software is an invisible element, it is the essential glue that binds the visible FMS equipment together and forms a system. Without these highly developed and sophisticated computer routines, an FMS is a mere collection of individually automated equipments on the factory floor.

    FMS software drives the entire system, calling various equipments to action through command driven operator and system manager input. Operating system software is the highest level, computer manufacturer specific, and executes supervisory control over the application software. Application Software is usually developed and supplied by the system supplier and includes all the FMS specific programs and routines. Application Software for an FMS is complex, highly proprietary. It is generally composed of several modules.

    Thus the inventory is maintained minimum that the manufacturing problems can be identified and solve it. Some of the ingredients are: Production 2. Simplicity 3. Standardization 4. Flexibility 5. These include 1. What do we start with? Where do we start? Who should do it? Factors for implementation are: The proposal for implementation will include explaining the requirements for a kanban system and designing the containers required for the system.

    The scope of the project ends with a summary of the report and other recommendations useful to the instructor. In general context, it refers to a signal of some kind. Thus, in the manufacturing environment, kanbans are signals used to replenish the inventory of items used repetitively within a facility.

    The kanban system is based on a customer of a part pulling the part from the supplier of that part. The customer of the part can be an actual consumer of a finished product external or the production personnel at the succeeding station in a manufacturing facility internal. Likewise, the supplier could be the person at the preceding station in a manufacturing facility. The premise of kanbans is that material will not be produced or moved until a customer sends the signal to do so.

    The typical kanban signal is an empty container designed to hold a standard quantity of material or parts. When the container is empty, the customer sends it back to the supplier. The container has attached to it instructions for refilling the container such as the part number, description, quantity, customer, supplier, and download or work order number. Some other common forms of kanban signals are supplier replaceable cards for cardboard boxed designed to hold a standard quantity, standard container enclosed by a painting of the outline of the container on the floor, and color coded striped golf balls sent via pneumatic tubes from station to station.

    They act as communication devices from the point of use to the previous operation and as visual communication tools. They act as download orders for your suppliers and work orders for the production departments, thereby eliminating much of the paperwork that would otherwise be required.

    In addition, kanbans reinforce other manufacturing objectives such as increasing responsibility of the machine operator and allowing for proactive action on quality defects. However, kanbans should not be used when lot production or safety stock is required because the kanban system will not account for these requirements. Traditionally, a push system is and has been employed.

    This system is based on the Planning Department setting up a long-term production schedule, which is then dissected to give a detailed schedule for making or downloading parts. This detailed schedule then pushes the production people to make a part and push it forward to the next station. The major weakness of this system is that it relies on guessing the future customer demand to develop the schedule that production is based on and guessing the time it takes to produce each part.

    Over- estimation and under-estimation may lead to excess inventory or part shortages, respectively. One of the major reasons kanbans are used is to eliminate or reduce the above mentioned wastes throughout an organization due to the pull system that is employed. Waste can come from over-production inventory and therefore, the need for a stockroom.

    This waste is eliminated. Part shortages under-production are also eliminated. Costs are reduced by eliminating the need for many of the downloading personnel and the paperwork associated with downloading. It is a more useful kanban technique in large-scale, high variety manufacturing facilities. In this system, each part has its own special container designed to hold a precise quantity of that part. Two cards are used: Each container cycles from the supplier workstation to its stock point to the customer workstation and its stock point, and back while one kanban is exchanged for another.

    No parts are produced unless a P- kanban authorizes it. There is only one C-kanban and one P-kanban for each container and each container holds a standard quantity no more, no less.

    Figure 3. The C-kanban is detached and placed in a collection box for Stock Point M. Standard container Flow path Kanban collection box E: The container that is most recently emptied in Drilling is taken to Stock Point M and a C- kanban is attached to it. The empty container and C-kanban are taken to Stock Point L where the C-kanban is detached and re-attached to a full container, which is taken back to Stock Point M.

    The full container taken to Stock Point M had a P-kanban attached to it. The P-kanban in the Stock Point L collection box are taken to Milling hourly where they go into a dispatch box and become the list of jobs to be worked on next at the Milling Station.

    For every job that is completed, parts go into an empty container from Stock Point L, and a P-kanban is attached. The full container is then moved back to Stock Point L. Essentially, the single-card kanban system is simply a dual-card kanban system with the absence of the production kanban and designated stock points.

    This system is demonstrated using the following diagram and the same workstations as the dual-card example where the stock points shown are the work stations themselves but are shown separately for explanation purposes: A container has just been emptied at the drilling station. The kanban is placed in the kanban collection box. The full containers at milling, with kanbans attached to them, are transported to drilling and the kanbans in the collection box are taken back to milling.

    Milling continues to fill containers depending on the demand from Drilling. Empty containers are collected from drilling periodically. Due to the inherent simplicity of the single-card kanban system and its applicability to the purposes of this report, the remainder of the report shall assume this technique is employed.

    Standard container Flow path E: GT is not simple the formation of machinery into manufacturing cells, but it involves bringing together and organizing common concepts, principles, problems, tasks, and technologies, to improve productivity.

    Group technology, like JIT is a journey, not a destination. It involves continuous improvement and structured discipline and must be a fundamental building block of a cell or system if the real benefits of automation are to be achieved. And it must be approached and applied before, during and after automation. It is implemented through the application of well-structured classification and coding systems and supporting software to take advantage of the similarities of components in terms of design attributes and processing sequences.

    The marketing challenges can be successfully met by GT.

    Today there is a trend in the industry towards low volume production of a wider variety of products in order to meet the raising demands for specially ordered products. The concepts of markets of yearly 20th century as vanished. The share of batch type production is growing every day and it is accepted that 75 per cent of all manufactured parts will be in small batch quantities.

    As a result of first factor, the conventional shop layout i. Modern management concepts like business process and reengineering highlight the need for breaking barriers between departments of an industry.

    GT and cellular manufacturing streamline material flow and reduced non-value adding activities. There is need to cut short the lad time, thus winning a competitive situation in the international market. From this type of layout there are advantages of reduced work pieces handling, lower set up times, less in process inventory and shorter lead-times. The main problem in switching over from conventional layout to GT layout is grouping parts into part families.

    GT gives the idea that many parts have similar geometric features, and by combining those design requirements a common part solution can be found. Parts may be arranged or grouped for GT technology through I. Design characteristics or features. Manufacturing process For grouping parts into part families there are three methods. They are 1. Visual Inspection. Part Classification and coding. Production flow analysis. It involves the classification of parts into part families by looking at either the physical parts or their photo groups and arranging them into graphs having similar features.

    Classification and coding are computerized tools used to capture the design and manufacturing features of part. They provide the ability to retrieve and analyze the data by desired feature. This is essentially the system of arrangement much like zip code or classification system used in library.

    When using alphanumeric codes, each position can have 26 different alternatives, but the values of alternates are only limited to 10per cent when numerical codes are used. Consequently alphabets are used to widen the scope of a coding scheme and make it more flexible. There are basically two types of coding systems. Mono codes, 2. Ploy codes 4. It is therefore essential that these codes are short and shape oriented.

    They are normally used for design storage and retrieval and not very useful for manufacturing application. Ploy code generally manufacture oriented, because its easily identifiable attributes help the manufacturing engineer to determine the processing requirements of parts. Never the less, poly codes tend to be long and digit location must be reserved whether that particular feature applies to a part or to a family of codes. It is therefore, a common industrial practice to use a hybrid construction combining the advantages of each of the two basic codes while eliminating their disadvantages.

    In a combination type, the first digit is the whole group of parts into sub groups 4. Parts, which may not be similar in shape but require similar sequence of operations, are grouped together to form a family. The resulting families are then used to design or establish machine cells. PFA employs clustering algorithms to manufacturing cells.

    After gathering the needed data, i. Each pack is given an identification number, and packs having similar routings are grouped together. Next zoning is used to identify the machine tools form rational machine cell. Engineering Design: Manufacturing Engineering: Production Control: Quality Control: Group Technology 37 Example 4. The from-to data for the machine is as follows: Hence machine 3 is placed at the beginning of the sequence. Eliminate the row and column of the corresponding to machine 3.

    Hence machine 1 is placed at the second of sequence. Eliminate the row and column of the corresponding to machine 1. The from—to data for the machine are as follows. The machine sequence is The flow diagram is given by 15 50 40 30 25 Parts Enter 3 2 1 4 Parts Exit 5 10 20 out Fig. An analysis of 50 parts which are processed on these machines provides the following from-to chart machines are identified by number.

    Determine from-to ratios and suggest a logical machine arrangement. The workflow is mostly in-line; however, there is some back flow of parts, which has to be considered in the design of any material handling system that may be used by the cell.

    A convey or might be used for the forward flow between machines, with less mechanized handling system for the back flow. The from—to data for the machines are as follows. Machine 1 and machine 2 are identical and are used to feed machine 3, which is the main machine in the cell.

    The output of machine 3 feeds into machine 4. The operation times for each part at each machine are given in the following table. Part Operation time min. If the hours worked per week are 35, determine how many of each product will be made by the cell? What are the utilization of the main machine and the utilization of the cell. Vertical machining centers continue to be widely accepted and used, primarily for flat parts and where three-axis machining is required on a single part face such as in mold and die work.

    Horizontal machining centers are also widely accepted and used, particularly with large, boxy and heavy parts and because they lend themselves to easy and accessible pallet shuttle transfer when used in a cell or FMS application. Selection of either a vertical or horizontal machining center mainly depends on the part type, size, weight, application, and in may cases, personal preference.

    Each has its own specific advantages and disadvantages. Generally, in vertical machining centers, the X-axis provides the longitudinal table travel, the Y-axis provides in and out saddle movement, and the Z-axis provides up and down movement of the head or spindle. Table indexing capability enables multiple sides of a work piece to be machined in one setting and clamping. Chips drop out of the way during machining providing an uncluttered view of the cut and preventing re-cutting of chips.

    Operators station is to one side of the column, providing good line of sight control 4. Ideally suited for large, boxy heavy parts 6. Overall, more flexible.

    As work piece size increases it becomes more difficult to conventionally look down into the cut 2. Extensive chip buildup obstructs view of the cut and re-cuts chips 3. On large verticals, head weights and distance from the column can cause head drop, loss of accuracy and chatter 4.

    Not suitable for large, boxy, heavy parts 5. The capability of machine tool to change its own cutting tools on command 2. An indexable work table permitting machining on multiple sides of a work piece in one clamping increased versatility of horizontal over vertical machining centers 3. The result is the emergence of the flexible manufacturing cell resident is a single machine; the machining center. Machining center automated features and capabilities perform various functions that now automates what was previously performed manually in several separate operations and on variety of different machine tools.

    Machining Centers 45 The principal automated machining center features and capabilities are 1. Torque control machining 2. Surface sense probe 3.

    Automated tool delivery 4. Multiple and angled spindle heads 5. Broken tool detection 5. The functions of torque control machining are to sense machining conditions and adjust the feeds and speeds to suit the real time condition. Sensing devices are built-into the machine spindle to sense torque, heat and vibration. These sensing devices provide feed back signals to the MCU, which has the preprogrammed safe limits. If the preprogrammed safe limits are exceeded, the MCU alters the feeds and speeds.

    Just as in rotational cells and systems, probing is of critical importance to the successful operation of our automated cell or system for prismatic parts. A probe is a multidirectional precision electronic switching device that can be held in the tool storage matrix, until called for by the part program.

    It is then positioned in the machine spindle just as if it were a standard tool with appropriate CNC— resident software and part programming. Machining center probes can 1. Check for part presence and alignment on single to multi part loaded pallets 2. Calculate the center position of a hole by averaging measured points taken around the hole or boss.

    Compute and store offset data in the fixture-offset table. Detect stock variations or cored hole shifts and automatically re-grid the machine Probing improves machining accuracy by feeding back offsets to fine tune the program in the range of 0. This technique by passes the need for extremely fine and costly drives and position measuring devices in the machine tool.

    Generally delivered on an AGV to the rear of the machine and tool matrix, new cutting tools can be exchanged with used tool without interference with the ongoing machining process. Multiple spindle heads, which can be loaded like an ordinary tool, drive a cluster of tools through their internal gearing mechanisms.

    The herd during contains a fixed number of driven spindles, but the location of each spindle relative to the others in determined by the downloadr, who can configure each individual spindle location to suit a repetitive hole pattern 90 and 45 angle.

    Heads are used on machining centers in highly specialized apparatus. In most cases, they are used where the investment in an angled spindle head to drill a few holes for example, may save another complete setup and part handling, just to drill a few difficult to get to holes. If a tool in broken, the machine will automatically replace it with a duplicate stored in the tool matrix. If the duplicate does not exist, a machine stop condition will occur and operator action is required.

    Broken tool detection adds to increased machine productivity and utilization and decrease operator involvement and attention. These burns are undesirable, particularly for precision components, as they may break loose and disturb a delicately balanced mechanism. They are also dangerous for the fingers. The work piece will also contain some oily unwanted substances such as grease, dust, and etc. The finished work piece with these unwanted materials cannot be a final finished product.

    So in order to deliver final finished products, the above-mentioned problems have to be overcome. These problems can be overcome by the techniques like deburring and cleaning. Actually, cleaning and deburring equipment do perform post-machining operations, but the automated processes add value, save time, and free employees to perform more meaningful work elsewhere.

    Parts must be cleaned and deburred before they can ever attempt to be accurately inspected, stocked or assembled. Although sometimes challenged because simple process require high priced equipment, how parts are cleaned and burrs removed are important factors to be considered in the planning of many flexible cells and systems. In past, deburring was purely a manual, repetitive process that was highly labor intensive. In many instances today, circumstances still require extensive manual effort for part deburring.

    However, over the last several years, various high-tech methods have emerged or have been perfected to deal with the problem of automating and reducing the manual effort required for burr removal. The 4 most common types of automated deburring are: Mechanical 2.

    Vibratory 3. Thermal energy 4. In many cases, conventional robots are not ideally suited for burr removal. Also many work pieces require different parts of the work piece. Parts systematically enter a large bowl container filled with ceramic pebbles commonly referred to as media. The size of the ceramic pebbles commonly referred to as media.

    The size of the ceramic media can vary depending upon the type, size and material of the parts to be deburred. As the parts enter the bowl via conveyor , the bowl is rapidly vibrated back and forth, this motion agitates the parts in the ceramic media, removing burrs, and gently polishing the parts.

    Here eccentric weights are mounted on each end of the bowl support shaft to vibrate the bowl in a controlled and adjustable manner. The parts to be deburred are sealed in a chamber, which is pressurized with a mixture of combustible gas and oxygen.

    This mixture completely envelops the parts and surrounds the burrs, regardless of external internal or blind hole location. This gaseous mixture is then ignited by a spark plug, which creates an instant burst of intense heat, and burrs, because of their high ratio of surface to area mass, burst into flames.

    Burrs and flash are instantly oxidized and converted to powder in approximately 25 to 30 seconds. Parts are then cleaned with a solvent.

    This process removes undesired material from all surfaces and eliminates follow-up inspection necessitated by inconsistent hand deburring operations.

    This process is effective for wide range of dissimilar parts of both ferrous and nonferrous materials. In this process an electrode is positioned close to area of workpiece made of conducting material to be deburred.

    The electrode is connected to the negative, and the work piece to the positive terminal of a D. An electrolyte is made to flow between electrode and workpiece. Thus electrochemical reaction takes place and burrs are removed. In this the current passed is directly proportional to burr removal rate. This process has several advantages like tool never touches the part, so no tool wear occurs. No heat is created during the process; therefore, thermal or mechanical stress cannot distort the part.

    Deburring and Wash Stations 49 6. Wash stations are automated high-tech washing machine that uses high-pressure coolant to remove the dirt, grease and chips from the part, fixture and pallet. Wash stations can accommodate a variety of different parts as long as the parts can fit within the required size limitations. They are n Batch type wash stations n In-line type wash stations 6. Batch wash stations are generally used in low-to mid-volume applications to provide a clean work piece for downstream inspection, assembly or further processing.

    In an in-line washer, workpieces are loaded at one end of a system, the work pieces are cleaned as they pass through the machine, and removed at the opposite end.

    Separate roller conveyors can be added at the load-unload sections for interfacing. Multiple stages can be added for rinsing, rust prevention, or part blow-dry. Selection of either a batch or In-line wash stations is a function of: For this Batch or In-line wash stations requires spray nozzle, which is to be properly sized, located and directed to clean exterior and interior areas of workpiece. In batch or in-line wash stations an adequate volume and pressure are required for complete flushing of chips from the workpiece fixture and pallet.

    These high-pressure wash stations operate at a 28bar or even more. This high pressure is capable of sharing of encrusted dirt and grease, resulting in a well-cleaned workpiece. Some heavy-duty batch wash stations are capable of automatically locking the pallet assembly to an internal machine circular rail carriage and rotating the entire assembly around the rail during the cleaning and blow-dry cycle. This allows better access to recessed areas, improved drainage and increased blow-dry coverage.

    This reduces drying time of the washed workpiece by blowing off the excess coolant or wash solution, prevents spillover to other machines and other areas of the cell, and helps keep the area clean and neat. Some machines use convector heated air blow-off generated by gas, steam, or electricity in order to speed up the blow- off and part drying cycle and to remove moisture.

    In-line wash stations generally have their own individual and cleaning solution storage tanks equipped for chip recovery and coolant or cleaning solution recirculation, where as in batch wash station the chip and coolant flow directly into the flume system trough to be circulated back to the central coolant storage tank.

    A sludge conveyor can be used on any type of wash station to handle any volume of dirt, chips. A sludge conveyor basically carries the waste material up to a slope to be deposited in a sludge container for disposal, while the liquid drains back into the central storage tank. Wash stations, like the other equipment in a FMS, receive instructions for the host computer or cell controller to their individual programmable controller.

    These instructions consists of signals primarily to: A typical batch wash stations operational scenario in an FMS would be: Among these key factors is the method for removal of burrs, chips, dirt, grease, tapping compound, and coolant from parts, fixtures and pallets. It is important to consider deburring and wash stations processes in an automated cell or system because they can: Deburring and Wash Stations 51 n Provide a cleaner and safer work environment.

    Of the two processes, cleaning and deburring, cleaning is more flexible and generally easier to add to a cell or system than deburring. Depending on part characteristics and other factors, it may not always be cheaper.

    Deburring has limited flexibility of operation, as we have already seen. Different types of deburring may be required for different parts of similar work-pieces. If work piece requirements change, the method and type of deburring may have to change. Wash stations, on the other hand, can accommodate a variety of different parts, as long as the parts can fit within the required size limitations. And batch wash stations must be able to accommodate the height and weight of tombstone fixtures.

    Consequently, how large a part and tombstone fixture can be accommodated by a particular wash station is an important factor to be considered in downloading. The problem with traditional measurement techniques is that each measured feature may require individual inspection instruments and individual setups, as well as allowing for increased human error.

    A coordinate measuring machine CMM can fill a valuable role in precision measuring because a surface plate, height gage and indicator inspection procedure are combined to provide a fast, accurate and more convenient alternative to the conventional methods for measuring complex parts.

    It seems that CMMs offer the answer to all our dimensional measurement problems, but is that really true? Will we get precisely the same results as the traditional methods? Measurement with a CMM is a complex process that requires the right training and interruption of data collected. Coordinate measuring machine is an electromechanical system designed to perform coordinate metrology.

    Coordinate metrology is concerned with the measurement of the actual shape and dimensions of an object and comparing these with the desired shape and dimensions, as specified by the part drawing. CMM evaluates the location, orientation, dimensions, and geometry of the part or object.

    A CMM consists of a contact probe that can be positioned in 3-D space relative to the surfaces of a work part. The x, y and z coordinates of the probe can be accurately and precisely recorded to obtain dimensional data concerning the part geometry See the Fig.

    Probe 2. Mechanical structure 7. The tip of probe is usually a ruby ball, which is used to make contact with the part surface during measurement. Ruby ball is usually made of corundum aluminum oxide , whose properties are high hardness for wear resistance and low density for minimum inertia. Probes can have either a single tip or multiple tips. Most probes today are touch-trigger probes, which actuate when the probe makes contact with the part surface.

    When contact is made between the probe and part surface, the coordinate positions of the probe are accurately measured by displacement transducers associated with each of the three linear axes and recorded by the CMM controller.

    Nearly all CMMs have a mechanical configuration that fits into one of the following six types: The quill can also be moved along the length of the arm to achieve y-axis motion, and the arm can be moved relative to the worktable to achieve x-axis motion.

    The advantages of this construction are: This provides a more rigid structure than cantilever design. One of the problems encountered with the moving bridge is yawing walking in which two legs of the bridge move at slightly different speeds resulting in twisting of bridge. This can be reduced by installing dual drives and position feedback controls for both legs.

    This bridge eliminates the yawing effect, hence increasing rigidity and accuracy. The arm moves vertically and in and out to achieve y-axis and z-axis motions. Large horizontal machines are suitable for measurement of automobile bodies.

    The probe quill moves relative to the horizontal arm extending between the two rails of the gantry. The x-axis and y-axis motions are achieved by moving the worktable, while the probe quill is moved vertically to achieve z-axis motion. Both types have various manufacturers and range in size from small tabletop models to the very large and expensive floor-mounted kind.

    CMMs are available with various computer peripherals and offer a variety of improved software packages, making systems integration of this equipment more practical.

    5 what is a flexible manufacturing system and under

    The measuring table and all the guide ways for example are constructed of high quality granite. Increased use of ceramics is also gaining wide acceptance. Floor preparation of coordinate measuring machines is also very important. Solid reinforced concrete foundations are required for vibration dampening. Sometimes CMMs require environmental control. Measured dimensions can only be as accurate and reliable as the stability of their surrounding environment.

    Axes movements in x, y and z are similar to other vertical and horizontal CNC equipment. During the automated inspection process, part dimensions are recorded with the help of probe. The CMM compares the result measurement with the previously input manufacturing tolerances allowed for each dimension and conveys this information to either the host or CMM computer.

    The CMM computer plays an important role in operation of coordinate measuring machine. In general its primary functions include: The docking procedure at the inspection station is controlled and monitored by a PLC Programmable logic controller. The parts to be inspected require preprogrammed inspection programs for each different wok piece.

    These reside at the host computer level in an FMS. Inspection programs are downloaded in demand to the CMM computer.

    Pallet and part identification are verified and the proper CMM inspection programs are automatically downloaded to the CMM computer. Inspection data from the CMM are automatically compared with pre-established tolerance bands in the CMM part programs.

    Inspection includes diameter, hole depth, flatness and depths of machined area. If a single work piece is rejected by a CMM, that pallet is automatically routed to material review station. If the part is rejected second time, the rejection is recorded in the associated work piece history file on the host computer and the pallet continues its predetermined routing. Deviations can be plotted to provide both graphical SPC and analytical inspection results with the appropriate quality and statistical process control software.

    Many inspectors performing repetitive manual inspection operations. If the inspection function represents a significant labor cost to the plant, then automating the inspection procedures will reduce labor cost. Post-process inspection. CMMs are applicable only to inspection operations performed after the manufacturing process. Measurement of geometric features requiring multiple contact points. Geometric features like angle between planes, flatness, etc. Multiple inspection setups are required if parts are manually inspected.

    Manual inspections are generally performed on surface plates using gage blocks, height gages, and similar devices and a different setup is often required for each measurement. The same group of measurements on the part can usually be accomplished in one setup on a CMM. Complex part geometry. If many measurements are to be made on a complex part, and many contact locations are required, then the cycle time of a DCC Direct Computer Control CMM will be significantly less than the corresponding time for a manual procedure.

    High variety of parts to be inspected. Repeat orders. Using a Direct Computer Control CMM, once the part program has been prepared for the first part, subsequent parts from repeat orders can be inspected. Reduced inspection cycle time: Because of the automated techniques included in the operation of a CMM, Inspection procedures are speeded and labor productivity improved.

    A CMM is a general—purpose machine that can be used to inspect a variety of part configurations with minimum changeover times. Reduced operator errors: Automating the inspecting process has an obvious effect of reducing human errors in measurements and setups. Greater inherent accuracy and precision: A CMM is inherently more accurate and precise than the manual surface plate methods that are traditionally used for inspection.

    Avoidance of multiple setups: Traditional inspection techniques often require multiple setups to measure multiple part features and dimensions. In general, all measurements can be made in a single setup on a CMM, thereby increasing throughput and measurement accuracy. Unlike traditional robots, AGVs are not manipulators, they are driverless vehicles that are programmed to follow a guide path. In offices they may be used to deliver and pick up the mail.

    They are even used to transport patrons around in airports. One of the first AGVs was a towing vehicle that pulled a series of trailers between two points. AGV systems did not catch on at that time; however, they were not well received by unions and were never allowed to perform to their full potential.

    The market has now grown to include the United States. The main benefit to AGVs is that they reduce labor costs. But in material handling facilities there is another benefit.

    Material handling has always been dangerous. Obstacle detection is therefore a key to allowing AGVs to interact with personnel safely while optimizing vehicle speeds.

    AGV technology has been moving forward. There have been advances in navigation systems. Until about10 years ago most AGVs followed electromagnetic wires buried in the floor.

    Then laser- guided systems came into the market.

    Similar posts:


    Copyright © 2019 podmimokongist.ga. All rights reserved.