Flexible Manufacturing Systems

In the field of manufacturing , many a times there is a need for a system which is different from the conventional manufacturing systems. Whenever a new product is designed for manufacturability it has the following characteristics;

• Low Cost

• High Quality

• Varying Designs

• Large Variety

• Small Volume

• Lesser Lead Time

Flexible Manufacturing System is a system which utilizes computer controlled equipment to integrate all the functions of a manufacturing system such that any kind of flexibility desired can be achieved. Flexibility is a vague term and needs to be carefully defined depending upon the requirements. These flexibilities can be;

• Machine Flexibility: It can be defined as the capability of machines to produce a wide range of product designs that may require different production techniques. It includes low setup or change over time for the workpiece on the machines, ease of reprogramming, sufficiently large tool storage capacity to incorporate various tools shapes n sizes and the skill and versatility of the machine operators.

• Production Flexibility: It can be defined as the range of various product shapes that can be produced using machine flexibilities.

• Product Flexibility: It can be defined as the ease with which changes in product designs can be accommodated in the manufacturing system.

• Mix Flexibility: It can be defined as the ability with which the product mix can be changed in a given manufacturing system.

• Routing Flexibility: It can be defined as the capacity to produce products through various routes or various process sequences via different machines in the factory in case of machine breakdown, tool failure and other interruptions.

• Volume Flexibility: It can be defined as the ability to economically produce parts in high or low quantities depending on the market demand at that moment. This depends on the amount invested in capital equipments and the efficiency of manual labors performing various operations.

• Expansion Flexibility: It can be defined as the ease with which the manufacturing system can be expanded to increase total production quantities in case of varying market demands. This involves considering the expenses required to buy new machines, making changes is layout of the entire factory with ease, type of material handling systems used and the ease with which trained workers can be increased on the shopfloor.

An FMS is a group of CNC machines that can randomly process a group of similar parts/or products. The FMS system has an Automated Material Handling System inbuilt. FMS uses a central computer control to dynamically balance resource utilization so that the system can adapt automatically to changes in part/or product production, mixes and levels of output.  FMS is a technology which will help achieve leaner factories with better response times, lower unit costs, and higher quality product under an improved level of management and capital control.

Thus FMS can handle a wide variety of dissimilar parts, producing them in small numbers even one at a time, in any order, as needed by making use of all the computer controlled equipments with the help of a central computer control. FMS not only brings flexibility but also increases responsiveness on the manufacturing floor. FMS enables manufacturers to develop products of wide variety on few machines with lesser number of staff, productively, predictably and reliably. FMS provides round-the-clock availability of automated equipment. FMS improves the response time to various problems on the shop floor such as;

• Product demand variation

• Design changes or Manufacturing process changes that can be easily adjusted by changing the CNC program which is developed by a CAD/CAM system as a part of the design change

• Machine unavailability can be easily taken care of by the FMS control system which can automatically transfer the part to another machine that is available

• Cutting tool failures during operation can be detected by sensors and stop the machine thereby reducing the catastrophic failures. The control system then can initiate steps to repair and replace the failed cutting tool

The important elements of an FMS are CNC machines, Material handling equipments, workpieces and tools. These elements are to be controlled in realtime which is done with the help of the FMS software which ensures timely supply of tools, workpieces and the required program for machining operation to the various machines connected to each other and controlled by a central computer. The various modules used in any FMS software are;

• Production Scheduling & Control – to schedule various production operations in the manufacturing system.

• Transport Management – to take care of the movement of material and tools on the shopfloor.

• Tool Management – to arrange the availability of the right tool at the right time and in the right condition at the right place.

• Simulation – for analyzing the factory operations before hand by simulation the entire assembly line before it is designed. Also used for product designing.

• Machine Diagnostics – for getting updates in real time about any malfunctioning of the machine during operation.

• Maintenance Planning – depending on the feedback received on the health of the machine, the maintenance schedule is planned.

Advantages of FMS:

• Improved product quality and reduced scrap rate

• Reduction in floor space used

• Reduced throughput time and its variability

• Reduced staff requirement

• Better competitive advantage

• Lower work in process inventories

• High productivity

• Better status monitoring of machines, tools and material handling devices

• Economic benefits in indirect labor due to reduced errors, rework, repairs and rejections

• Allows changing product volumes and different product mixes

• Reduced product life-cyle time and cost

• Improved Supplier relationship

Disadvantages of FMS:

• FMS is a very sophisticated system and technologically advanced hence it requires very high level planning

• FMS requires very high capital investment

• Worker education and training on the sophisticated equipments is an added cost

• Requires considerable amount of time to be developed

• Not very easily adopted by manufacturing firms

• Partially obsolete systems

• Changes in management philosophy & lack of top management commitment and support

• Misconceptions by companies that FMS is applicable only for large scale production

Japan and Germany are one of the leading companies adopting FMS. Aerospace, automotive, machine tools, power and defence industries in USA, France, Russia and UK use FMS.

Examples of some firms using FMS completely or partially;

1. Boeing’s aircraft components manufacturing plant in Auburn, WA

2. Chrysler’s Toronto plant

3. Ford’s sheet metal parts manufacturing plant in New Holland, PA

4. Mazak’s parts for machine tools manufacturing plant in Florence, Ky

5. General Electric

6. Levis Strauss uses FMS to make jeans for women that fit them exactly

7. Allen Bradley

8. Hughes aircraft plant in California

9. Goodyear tire manufacturers use FMS, etc

FMS is also called Agile Manufacturing since it is a technology adopted to achieve agility by manufacturers. An agile manufacturer is one who is the fastest in responding to the market changes, operates with the lowest total cost and has the greatest ability to provide customer satisfaction. Hence FMS is a necessity rather than a luxury for most of the manufacturers in the competitive world today!

References 

Automation, Production systems and Computer Integrated Manufacturing by M P Groover

Cad/Cam Principles and Applications by P N Rao

About the Author : Sharmeen Sahibole is a student of M.E. Robotics.  Views are personal.

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