Computer- integrated manufacturing: What is computer-integrated manufacturing?

What is computer-integrated manufacturing?

Computer-integrated manufacturing (CIM) covers a range of technologies and techniques that seek to use the power of the computer to ensure that all activities, equipment, and processes in a manufacturing organization work together in the most effective way to achieve its objectives.

The word 'integrated' means that CIM is more than merely the piecemeal application of the automated produc­tion techniques described later in this chapter - robots, NC machines, automatic materials handling, and so on. A central concern is the flow and the use of information, so that each part of the organization, whether sales, purchas­ing, warehousing, or production, knows at any point in time exactly what it should be doing in order to be properly integrated into other activities and so optimize overall performance. This means that data has to be processed and passed between the various systems and machines, and so CIM is heavily dependent upon data processing.

The technologies and techniques that are embraced by CIM can be split into four broad areas:

• Techniques for planning manufacturing.

• Techniques for controlling manufacturing.

• Techniques for executing manufacturing.

• Techniques for integrating manufacturing.

Some of these techniques are described in this chapter. Here's a comprehensive (though not exhaustive) list of them:

Techniques for planning manufacturing

Computer-aided design (CAD)

Computer-aided process planning (CAPP)

Manufacturing resources planning (MRP)

Just-in-time (JIT)

Optimized production technology (OPT)

Techniques for controlling manufacturing

Work-in-progress (WIP) planning and control Automatic materials handling (AMH)

Quality assurance (QA)

Engineering data management (EDM)

Techniques for executing manufacturing

CNC (computer-numerically-controlled) machines and robotics

Flexible manufacturing systems (FMS)

Techniques for integrating manufacturing

Connectivity issues, including networking standards such as Manufacturing Automation Protocol (MAP).

Note also the following terms:

• CAM (computer-aided manufacture) - used to describe a combination of CNC machines, robots, and automatic materials handling.

• CAD/CAM - used to describe the linking of CAD to CAM, a technique which enables designs created in the drawing office to be passed electronically direct to CNC machines and robots in the factory, which automatically convert them to parts and products.

10.2 The evolution of manufacturing technology

The enormous wealth of the industrialized world has been created by the application of technology to manufacturing.

The great evolutionary epochs of the past are well known: the stone age, the iron age, and the age of mechanization (the industrial revolution). Each was the result of a major technological advance, and each has resulted in huge gains in manufacturing productivity and wealth.

We are now into the next epoch, the age of information. The technological advance that ushered in this age (the silicon chip) was described at the start of this book. So far as manufacturing is concerned, the end result of the information revolution will be the appearance of radically new types of factories, and the integration of the whole manufacturing process from the supply of materials and parts to the distribu­tion of the finished goods. The effect of this on society and wealth is difficult to predict, but it will certainly be enormous. (Its impact on employment is discussed in the next chapter.)

The application of computers to manufacturing began around 30 years ago. Since then, there has been a steady evolution in computer-based factory automation techniques, accompanied by a gradual progression towards greater levels of integration. This evolution has, to a large extent, been governed by developments in computers over the last three decades.

The 1960s. Computers were first applied to manufactur­ing in the early 1960s. These were the days of the early batch-processing mainframe computers, which were suitable for data processing (DP) tasks but not for controlling factory equipment (see later). Consequently it was the DP side of manufacturing that was computerized, the principal tech­nique that we have inherited from that time being MRP.

The 1970s. Then, in the 1970s, new types of computers came along (see page 44). Their significance for manufactur­ing was that they were able to respond instantaneously to data received from sensors. Individual machines, groups of machines, and processes could now be brought under com­puter control. However, the lack of standards at this time, and the proliferation of differing approaches, meant that these computer-controlled devices were not linked together but worked largely independently of each other. This resulted in the so-called 'islands of automation' (see the next para­ graph). During the 1970s, the base technologies of modern manufacturing automation were developed, such as com­ puter-numerically-controlled (CNC) machines and robots, computer-based statistical quality control techniques, and computer-aided design (CAD).

The term 'islands of automation' has been coined to describe the many different computer-controlled devices within a factory that work with little reference to each other, i.e. with no provision for data to pass between them. One example was the use of computers for statistical quality control - these could rapidly signal deviations in the output of a process outside the accepted tolerance limits, but they could not stop the process for the fault to be rectified. This meant that the overall control and coordination of the process was carried on much as before, i.e. by manual rather than electronic methods.

As indicated above, this lack of communication between automated equipment was due to the lack of agreed stan­dards, rather than being an inherently difficult task. Indeed, while the physical work that lathes and millers (for instance) might do is different, the task of controlling them is actually very similar, using devices called programmable logic con­trollers (PLCs).

The 1980s. The 1980s has been the decade of the per­sonal computer and computer networks. It is the latter that has been particularly significant for manufacturing, for it has enabled many different computers and pieces of equip­ment to be linked together electronically. ('Connectivity' is the term that's often used to describe this.) This is bringing about the next phase of the evolution in factory automation, namely the setting up of connections between the islands of automation, and between these islands and a supervisory computer. A demonstration of this is the linking of CAD systems to manufacturing systems, so that designs produced in the drawing office are sent electronically to the factory machines, where, with the minimum of human intervention, they are converted to products. This linkage leads to further productivity and performance gains. It also allows the power of the computer to be used to integrate the various pro­ cesses, ensuring that they work together to optimize the performance of the enterprise as a whole. The term computer-integrated manufacturing (CIM) is specifically applied to this development.

The 1990s. It looks like the 1990s will be the age of telecommunications, resulting in connectivity not just within an organization but between organizations. An example of the trend towards this is the growing number of companies communicating with each other using Electronic Data Inter­ change (EDI) technology (see page 191). EDI allows stan­dard electronic 'forms' -such as purchase orders or invoices - to be passed between the computers of different organiz­ations, cutting out postal delays and saving storage space and paperwork handling costs.

This type of development will lead to the integration of factory systems with the systems of outside suppliers and customers. Some organizations are already moving in this direction, prompted mainly by the development of just-in­ time (JIT) techniques, which aim to cut inventories and improve efficiency by ensuring that supplies of materials and parts arrive at the point of production immediately prior to manufacturing. The successful application of JIT depends partly on the supplier of materials and parts responding rapidly to a customer's requirements, which in turn depends upon his manufacturing and distribution systems receiving timely data via EDI from the customer's manufacturing systems. This is best achieved by electronic links between the computers of the two organizations, and from there it is but a short step to arranging that the supplier's factory responds automatically to demands from the customer's factory.

Another result of the development of telecommunications is the concept of the 'global shop floor'. Many organizations have geographically-dispersed factories, with different parts of the production process carried out in different countries, and so they need to apply CIM concepts across national frontiers. Groups of machines need to be linked not just to other equipment in their own factory but to equipment in other factories in the organization. The systems that have evolved track work-in-progress (WIP) not just in the individ­ual factory but throughout the entire organization.

The impact of CIM

There are, as yet, no factories which are integrated to the extent that all operations- from order to processing through design and manufacture to distribution - are centrally con­ trolled and coordinated by computer. Indeed, in many cases it is not desirable to aim for such a high level of integration and automation. Where factory automation has been applied, the aim so far has been to integrate some parts only of the enterprise. Here are three examples:

• In one organization, CAD/CAM might be applied. This integrates and automates the design and manufacturing processes, but it impinges only marginally on other areas.

• In another organization, JIT might be applied. This integrates manufacturing and distribution, but has lim­ited impact elsewhere.

• Yet another organization might apply both CAD/CAM and JIT. Although this extends the degree of integra­tion, there are many activities still excluded.

DP and CIM

Traditionally, data processing (DP) has impacted mainly the business operations area, being concerned with the auto­mation of order processing, stock control, and accounts. However, with the replacement of islands of automation by CIM, DP has come to play a crucial role in engineering operations and production as well.

A very simplistic view of how DP and factory automation work together is shown in Figure 10.1. Customer orders are input to the DP system, one output being the production plans which tell the CAM system in the factory what to make. Another output from the DP system is reports that analyse sales and customer preferences, which can be used by the design function as a basis for product improvements. The designs, created on the CAD system, are passed to the CAM system, where they are converted into finished products.