Flexible manufacturing systems (FMS)

Introduction ,FMS Equipment,FMS Layouts ,Analysis Methods for FMS,,advantages of fms,comparison of fms to conventional methods,applications.Benefits of fms.

1. Flexible Manufacturing Systems (FMS)

2. Introduction A FMS consists of a group of programmable production machines interconnected by means of an automated material handling and storage system and controlled by an integrated computer system to produce a variety of parts at non- uniform product rates, batch sizes and quantities . A FMS is characterised by the following: Variety of products ,small volume of products, Less manufacturing lead time ,high quality , Low cost.

3. What is FMS ? A flexible manufacturing system is an automated Machine cell , consisting of a group of processing work stations, interconnected with automated material handling and storage system.

4. FMS Equipment In general FMS equipments consists of the following components: 1.Manufacturing system. 2.Tool handling and storage. 3.Material handling and storage. 4.Computer control system.

5. 1.Manufacturing System The machining system consists of CNC Machine tools (including Horizontal centre, Vertical centre , Turning centre) that can perform machining operations on part families. However FMS also include ASSEMBLY STATIONS , SHEET METAL PRESSES , INSPECTION STATIONS Manufacturing system capable of performing several operations on the work piece automatically

6. Machining centres consist of an automatic tool changing and tool storage , pallet changer, CNC Control and DNC control. Assembly workstations are used for assembly products typically made in batches Industrial robots are usually considered to be the most appropriate as automated workstations INSPECTION STATIONS are incorporated into FMS by including an inspection operation at a given work station or by designating a specific station for inspection. SHEET METAL PROCESSING MACHINES consist of press working operations such as punching , shearing and bending and forming processes

7. 1.Manufacturing system.

8. 2. Material Handling and Storage This system facilitates the timely supply of un machined work pieces from the storage to the machining centres and transport of the machined parts from machining centres to the desired locations. Functions of material handling and storage system are Random , Independent movement of work pieces between work stations Accommodation of different part configurations: Example : F or prismatic parts , the fixture is located on the top of pallet and is designed to accommodate different part configurations For rotational parts , industrial robots are used to load and unload the machine tools and to transfer parts between workstations. c) Compatibility with computer control: The handling system is allowed to control directly by the computer to direct to workstation, load and unload workstation.

9. The material handling equipments consists of 1.load/unload stations(palletising) 2.Robotics 3.AGV (AUTOMATICALLY GUIDED VECHICLE) 4.AS/RS (Automatic storage and Retrieval system)

10. Prismatic components are set up on pallets. Fixture are used to locate the parts precisely on the pallets Figure show FMS with a rail – mounted transport vehicle and stationary pallets. FMS fixtures can accommodate part families and minimise changeover times.

11. Modular fixturing

12. A typical AS/RS is shown Work piece storage and retrieval can be automated by using an automatic storage retrieval system (As/Rs). AS/RS consists of storage racks , a PLC based or computer-controlled stacker crane. Servomotors used in the cranes can achieve positioning accuracy and reliability. Elevating speeds of the stacker could be as high as 180 m/min.

13. AGV An automatically guided vehicle (AGV) is a material handling system which uses independently operated , self – propelled vehicles that are guided along defined pathways in the floor. This vehicles are power by means of on- board batteries. A typical AGVS unit load carrier is shown. It is equipped for automatic loading and unloading by means of P owered rollers , Moving belts , Mechanised lift platforms or other devices.

14. 3.Tool Handling storage In a FMS , various cutting tools are loaded onto the machine at intervals depending upon their utilisation. The cutting tools are stored in auxiliary tool storage from where the required tools can be transferred to the main tool magazine. Such storage units include drums ,chains, discs and other forms. There is limit to the maximum number of tools available at the machine tool (20-120).

15. 4.FMS Control System All the elements in an FMS , Machine tools , Material handling units and cutting tools are to be controlled in real – time. A computer is used to control the operation of FMS Functions performed by the FMS computer control are: 1.Control of workstations 2.Production control. 3.Traffic control. 4.Shuttle control. (secondary part handling system) 5.Tool control. (Tool location Accounting and Tool life Monitoring) 6.Scheduling. 7.System performance and Monitoring

16. FMS Layouts The FMS layouts are Broadly Classified into the Following Five categories: 1.IN – Line. 2.Loop. 3.Ladder. 4.Open – field. 5.Robot – centred cell.

17. 1.In – line or progressive FMS layout It is most appropriate for systems in which the work parts progress from one workstation (WS) to the next in a well – defined sequence with no back flow.

18. 2.LOOP FMS Layout: In this layout work part usually flow in one direction along the loop with the capability at any workstation The load/unload stations are located at one end of the loop .

19. 3.Ladder FMS Layout : This type of layout contains rungs on which workstations are located This layout reduces the average distance travelled to transfer work parts between stations.

20. 4.Open – field FMS layout The open field layout configuration consists of Loops ,ladders, and sliding organised to achieve the desired processing requirements This is appropriate for a large family of parts.

21. 5.Robot – centred FMS layout In this the robot is located at the approximate centre of the layout and the other workstations are arranged around it Industrial robot equipped with grippers may be used for the handling of rotational parts . The type of layout is well – suited for handling of cylindrical or disk shaped parts.

22. Analysis Methods for FMS FMS is a complex system for study and analysis. the Quantitative analysis of FMS can be accomplished or ready by using a number of different mathematical modelling techniques. The basic techniques are as follows: 1 .Static or Deterministic model. 2 .Queuing models. 3 .Perturbation analysis (Disturbance). 4 .Simulation.

23. 1.Static or Deterministic models: These models are used to estimate production throughout , capacity and utilisation . Operating characteristics of the production cannot be evaluated by using this models. A) The manufacturing lead time (MLT) is the total time Required to process a given product throughout the plant The mathematical expression is given by where T s i = Set –up time. T o i = Time per operation at a given workstation. T n i = Non-operation time Associated with the same workstation. I= is operation sequence in the processing i =1,2,3,4,m

24. 2.The production capacity (PC) for the Group of work Centres is given: PC= WS w HR P where where W is the number of work centres 1. S w = Number of shift per week 2. H = Operating time in hours of each work centre. 3. R P = Production rate , units per hour. 3. Utilisation (U) is the amount of a production facility relative to its capacity U = Output / Capacity. 4. work-in- progress is the amount of product currently located in the plant that is either being processed or between processing operations. The work-in-progress is given by WIP = (PC) U (MLT)/ S w H

25. 2. Queuing Models: This model is based on mathematics of queues. Queuing models are useful in the preliminary design of manufacturing systems but are not accurate enough at the detailed design/operation stage .

26. 3.Perturbation Analysis This model enables parameter sensitivities to be computed in real-time Perturbation Analysis works by observing nominal experiment, which could be on the actual system or based on the simulation By performing simple computations, solutions can be obtained questions such as: What will be the performance index if the machines are faster ?

27. 4.Simulation Discrete event simulation on a computer offers the most flexible approach for modelling the FMS. There are three approaches to simulation modelling of FMS I. a)Network or graphical models : In these model objects are represented by graphical symbols placed in the same physical relationship to each other as the corresponding machines are in the real world b) SLAM and SIMAN are two widely used networking tools for FMS. II. Data – Driven models : It consists of only numerical data example: The numerical data may be a) A simple count of machines in a system or b) A table of operation times for each process on the route for a given product. III. Programming language models: These provides activity cycles , queues and an optimum cycle. 1.Activity cycle diagram (ACD) Is widely used for FMS simulation 2.It is equivalent to a flow chart of a general purpose computer program 3.The ACD shows the cycles for every activity in the model.

28. 1.External changes such as change in product design and production system. 2.Optimizing the manufacturing cycle time 3.Reduced production costs 4.Overcoming internal changes like breakdowns etc. 5.Lower cost per unit produced 6.Greater labour productivity 7.Greater machine efficiency 8.Improved quality 9.Increased system reliability 10.Reduced parts inventories

29. 11.To reduce set up and queue times 12.Improve efficiency 13.Reduce time for product completion 14.Utilize human workers better 15.Improve product routing 16.Produce a variety of Items under one roof 17.Improve product quality 18.Serve a variety of vendors simultaneously 19.Produce more product more quickly 20.Adaptability to CAD/CAM operations 21.Shorter lead times

30. 1.Expensive. 2.Substantial pre-planning activity. 3.Cost to implement, 4.Substantial pre-planning 5.Requirement of skilled labour 6.Complicated system CHALLENGES 1.Determining if FMS the best production system for your company 2.Possible expansion costs associated with implementing FMS

31. Benefits of FMS Greater flexibility Higher machine utilisation Reduced work-in- progress Lower manufacturing lead times Higher labour productivity

32. Metal-cutting machining Metal forming Assembly Joining-welding ( A rc , S pot) Surface treatment Inspection Testing

33. Thank U Boshalla