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Sunday, October 26, 2008

Flexible Manufacturing Systems [F.M.S] : Whitepaper 01

An old Whitepaper [my first] that I had co-authored eons ago while in the Second Year of Engineering. Being released as-is without any update

Read the previous parts: Abstract


Since the dawn of civilisation, man has been continuously trying to ease and improve his work by developing better tools. This process started with the development of stone tools and will culminate into development of a totally automated factory. This factory would be able to do all the things associated with a product, right from designing it to packaging. Since the human operator tends to be the weakest link in the production process, the need for automation has been felt throughout the industry.

A Flexible Manufacturing System (F.M.S.) is a part of this process and a step towards complete automation of the factory. This system automates the metal cutting part of the product manufacturing. A F.M.S. is a form of flexible automation in which several machine tools are linked together by a material-handling system, and all aspects of the system are controlled by a central computer1.

Why use F.M.S.?

The current market scenario is such that a customer has the requirement to demand a wide variety of good quality product at a very short notice. The traditional systems of product manufacture like Transfer Line system were unable to cope up with the market requirements. The Transfer Line system of manufacture had a very high production level but offered limited flexibility. On the other hand, Workshop system of product manufacture offered a very high degree of flexibility but had a very low production level. These systems were unable to satisfy the requirements of variety, quantity and speed at the same time. This lead to the work of development of a system, which combines the seemingly conflicting objectives of high flexibility and high productivity.

The emergence of F.M.S. technology has proved to be an ideal solution to this problem. With the help of F.M.S. we are able to produce a wide variety of products without making any changes in the hardware set-up. As a result of this the changeover time between two products can be reduced to the time required by the machine tools to receive the necessary instructions. It also reduces the lead-time drastically. This is of prime importance as lead-time is equated with the cost of the product. It is a market-sensitive technology as it can produce the required proportion of product variety quickly and efficiently.

Flexible Manufacturing System [F.M.S]

Figure 1: - Volume versus variety capabilities of various Manufacturing Systems,

Courtesy Material and Processes in Manufacture, Lindberg

What is F.M.S.?

It is a collection of production equipment logically organised under a host computer and physically connected by a central transport system.

It is group of manufacturing cells linked by an automatic material handling system and a central computer. It is able to manufacture a mix of piece-part types while being flexible enough to sequentially manufacture different piece-part type mixes without costly, time-consuming, changeover requirement. It is a medium size batch production system. The parts requiring the same machining operation is sent to the to the appropriate machine tools irrespective of the type of part.

Flexible Manufacturing System [F.M.S]

Figure 2: - Block Diagram of a Flexible Manufacturing Cell (F.M.C.),

Courtesy Flexible Manufacturing systems in Practice, Bonneto

It basically contains a number of machining cells called Flexible Manufacturing Cells (F.M.C.), Figure 2. These cells if installed as stand-alone entities can offer a certain amount of flexibility in machining. A typical F.M.C. consists of a C.N.C. machine with a transfer system to load and unload the work piece and a tool magazine. The work pieces move from machine to machine in a sequence independent of the physical arrangement of the machine tools.

When a number of F.M.C.s are integrated together with a common controller called Distributed / Direct Numerical Controller and a Material Handling System and Tool Handling system it evolves into and a Flexible Manufacturing System. Each unit has its own Controller (either D.N.C. or P.L.C.) whose activities are in turn co-ordinated and supervised by the central host computer. This interaction between the Hardware and Software modules results into an organisation capable of performing multiple machining operations.

Components of F.M.S.

Components of a F.M.S. can be broadly classified into two categories.

  • Hardware

  • Software

Flexible Manufacturing Systems [F.M.S]

Figure 3: - The generalised Block Diagram of an F.M.S., courtesy Flexible Manufacturing, Parrish


Hardware: -

The Hardware component (Figure 3) basically consists of Machine

Tools and Handling systems.

It incorporates the following equipments

  • Machine Tools e.g., Universal Machining Centres, Turning Centres, Drilling Machines etc

  • Host Computer.

  • Load/ Unload station

  • Guided Vehicles e.g., wire-guided trolley, shuttle, over-head conveyor etc

  • Robots

  • Washing station

  • Tool Room

  • Swarf Disposal System

  • Inspection Hardware (C.M.M. facilities)

  • Programmable Logic Controllers (P.L.C.)

Software: -

Software for F.M.S. can be divided into 2 broad categories – extrinsic functions and intrinsic functions (Figure 4).

Software for the extrinsic functions is used to plan and control the functions that take place outside the physical boundaries of the F.M.S.2

Software for the intrinsic functions is used to load and control the components within the physical boundaries of the F.M.S.2

Flexible Manufacturing System [F.M.S]

Figure 4: - Extrinsic and intrinsic functions of F.M.S., courtesy Handbook of Flexible Manufacturing Systems

Extrinsic Functions incorporate the following operations: -

  • Production Scheduling

  • Process Planning

  • Tool Management

  • Maintenance Planning

Intrinsic Functions incorporate the following operations: -

  • Production Control

  • Production Monitoring/ Reporting

  • Machine/ Process Control

  • Machine Diagnostic

Read the remaining parts: Part 2, Part 3