1.1 AUTOMATION DEFINED

Automation is a technology concemed with the application of mechanical, electronic, and computer-based systems to operate and control production. This technology includes :

• Automatic machine tools to process parts
• Automatic assembly machines
• Industrial robots
• Automatic material handling and storage systems
• Automatic inspection systems for quality control
• Feedback control and computer process control
• Computer systems for planning, data collection, and decision making to support manufacturing activities

The scope of this text will be limited primarily to automated systems used in discrete-product manufacturing. Examples of industries using these types of systems include : metalworking, electronics, automotive, appliances, aircraft, and many others.

Types of automation
For our purposes in this book, automated production systems can best be classified into three basic types :

1. Fixed automation
2. Programmable automation
3. Flexible automation

Fixed automation is a system in which the sequence of processing (or assembly) operations is fixed by the equipment configuration, The operations in the sequence are usually simple. lt is the integration and coordination of many such operations into one piece of equipment that makes the system complex. The typical features of fixed automation are :

• High initial investment for custom-engineered equipment
• High production rates
• Relatively inflexible in accommodating product changes

The economic justification for fixed automation is found in products with very high demand rates and volumes. The high initial cost of the equipment can be spread over a very large number of units, thus making the unit cost attractive compared to altemative methods of production. Examples of fixed automation include mechanized assembly lines (starting around 1913 - the product moved along mechanized conveyors, but the workstations
along the line were manually operated) and machining transfer lines (beginning around 1924).

ln programmable automation, the production equipment is designed with the capability to change the sequence of operations to accommodate different product configurations. The operation sequence is controlled by a program, which is a set of instructions coded so that the system can read and interpret them. New programs can be prepared and entered into the equipment to produce new products. Some of the features that characterize programmable automation include :

• High investment in general-purpose equipment
• Low production rates relative to fixed automation
• Flexibility to deal with changes in product configuration
• Most suitable for batch production

Automated production systems that are programmable are used in low and medium-volume production. The parts or products are typically made in batches. To produce each new batch of a different product, the system must be reprogrammed with the set of machine instructions that correspond to the new product. The physical setup of the machine must also be changed over: Tools must be loaded, fixtures must be attached to the machine table, and the required machine settings must be entered. This changeover procedure takes time. Consequently, the typical cycle for a given product includes a period during which the setup and reprogramming takes place, followed by a period in which the batch is produced. Examples of programmable automation include numerically controlled machine tools (first prototype demonstrated in l952) and industrial robots (initial applications around 1961), although the technology has its roots in the Jacquard loom (1801).

Flexible automation is an extension of programmable automation. The concept of flexible automation has developed only over the last 15 or 20 years, and the principles are still evolving. A tlexible automated system is one that is capable of producing a variety of products (or parts) with virtually no time lost for changeovers from one product to the next. There is no production time lost while reprogramming the system and altering the physical setup (tooling, fixtures, machine settings). Consequently, the system can produce various combinations and schedules of products, instead of requiring that they be made in separate batches. The features of flexible automation can be summarized as follows :

• High investment for a custom-engineered system
• Continuous production of variable mixtures of products
• Medium production rates
• Flexibility to deal with product design variations

The essential features that distinguish flexible automation from programmable automation are : (1) the capacity to change part programs with no lost production time, and (2) the capability to change over the physical setup, again with no lost production time. These features allow the automated production system to continue production without the downtime between batches that is characteristic of programmable automation. Changing the part programs is generally accomplished by preparing the programs off-line on a computer system and electronically transmitting the programs to the automated production system. Therefore, the time required to do the programming for the next job does not interupt production on the current job. Advances in computer systems technology are largely responsible for this progamming capability in flexible automation. Changing the physical setup between pans is accomplished by making the changeover off-line and then moving it into place simultaneously as the next part comes into position for processing. The use of pallet fixtures that hold the parts and transfer into position at the workplace is one way of implementing this approach. For these approaches to be successful, the variety of pans that can be made on a flexible automated production system is usually more limited than a system controlled by programmable automation. Examples of flexible automation are the llexible manufacturing systems for perfonning machining operations that date back to the late l960s.

The relative positions of the three types of automation for different production volumes and product varieties are depicted in Figure 1.1.

Computer integrated manufacturing
The computer has had and continues to have a dramatic impact on the development of production automation technologies. Nearly all modem production systems are implemented today using computer systems. The term computer integrated manufacturing (CIM) has been coined to denote the pervasive use of computers to design the products, plan the production, control the operations, and perform the various business related functions needed in a manufacturing fimt. CAD/CAM (computer-aided design and computer-aided manufacturing) is another term that is used almost synonymously with CIM.

FIGURE 1.1 Three types of production automation as a function of production volume and product variety.

Let us attempt to define the relationship between automation and CIM by developing a conceptual model of manufacturing. ln a manufacturing firm, the physical activities related to production that take place in the factory can be distinguished from the information-processing activities, such as product design and production planning, that usually occur in an office environment. The physical activities include all of the manufacturing processing, assembly, material handling, and inspections that are perfomied on the product. These operations come in direct contact with the product during manufacture. They touch the product. The relationship between the physical activities and the information-processing activities in our model is depicted in Figure 1.2. Raw materials fiow in one end of the factory and finished products fiow out the other end. The physical activities (processing, handling, etc.) take place inside the factory. The information-processing functions form a ring that surrounds the factory, providing the data and knowledge required to produce the product successfully. These information-processing functions include (1) certain business activities (e.g., marketing and sales, order entry. customer billing, etc.), (2) product design, (3) manufacturing planning, and (4) manufacturing control. These four functions form a cycle of events that must accompany the physical production activities but which do not directly touch the product.

Now consider the difference between automation and CIM. Automation is concemed with the physical activities in manufacturing. Automated production systems are designed to accomplish the processing, assembly, material handling, and inspecting activities with little or no human participation. By comparison, computer integrated manufacturing is concerned more with the information-processing functions that are required to support the production operations. CIM involves the use of computer systems to perfomi the four types of information-processing functions. Just as automation deals with the physical activities, CIM deals with automating the information-processing activities in manufacturing. The growing applications of computer systems in manufacturing are leading us toward thc computer-automated factory at the future.

FIGURE 1.2 Model of manufacturing, showing (e) the factory as a processing pipeline where the physical manufacturing activities are performed, and (b) the information-processing activities that support manufacturing as a ring that surrounds the factory.

We will return to our model of manufacturing in Chapter 2 and to the topics of CIM, CAD/CAM, and the future automated factory in the final chapters. For now let us consider some of the more general issues related to automation and computer-integrated manufacturing.