2.2 TYPES OF PRODUCTION

Another way of classifying production activity is according to the quantity of product made. ln this classification, there are three types of production :

1. Job shop production
2. Batch production
3. Mass production

This classification is normally associated with discrete-product manufacture, but it can also serve for plants used in the process industries. For example, some chemicals are produced in batches (batch production), whereas others are produced by continuous-flow processes (mass production). The three types of production are related to production volume as shown in Figure 2.l.
JOB SHOPS. The distinguishing feature of job shop production is low volume. The manufacturing lot sizes are small, often one of a kind. Job shop production is commonly used to meet specific customer orders, and there is a great variety in the type of work the plant must do. Therefore, the production equipment must be flexible and general-purpose to allow for this variety of work. Also, the skill level of job shop workers must
be relatively high so that they can perform a range of different work assignments. Examples of products manufactured in a job shop include space vehicles, aircraft, machine tools, special tools and equipment, and prototypes of future products.

chapter 2 Production Operations and Automation Strategies

Production is a transformation process that converts raw materials into finished products that have value in the marketplace. The products are made by a combination of manual labor, machinery, tools, and energy. The transfomiation process usually involves a se quence of steps, each step bringing the materials closer to the desired tinal state. The individual steps are referred to as production operations.
ln this chapter we define some fundamental concepts about production and automation. We begin by examining the industries that are engaged in manufacturing. This leads into the types of production and the various functions that are associated with it. Many of the functions can be described by mathematical models, and several equations are derived to define concepts such as production rate and plant capacity. The chapter concludes by developing a list of I0 automation strategies. These strategies form the basis for the specific topics covered in this book.

2.1 MANUFACTURING INDUSTRIES
There is a wide variety of basic industries, including not only manufacturing but all others as well. By examining the publicly held corporations whose shares are traded on the major stock exchanges, it is possible to compile a list of industry types. Such a list is presented in Table 2.l. This list includes all types of industrial corporations, banks, utilities, and so on. Our interest in this book is on industrial firms that are engaged in production. 

 TABLE 2.1 Basic Industries : General

Advertising
Aerospace
Automotive (cars, micks, buses)
Beverages
Building materials
Cement
Chemicals
Clothing (gaments, shoes)
Construction
Drugs, soaps, cosmetics
Equipment and machinery
Financial (banks, investment companies. loans)
Foods (canned, dairy, meats. etc.) .
Hospital supplies
Hotel/motel
lnsuranceMetals (steel. aluminum, etc.)
Natural resources (oil, coal, forest, etc.)
Paper
Publishing
Radio, TV, motion pictures
Restaurant
Retail (food, department store, etc.)
Shipbuilding
Textiles
Tire and rubber
Tobacco
Transportation (railroad. airlines, trucking. etc.)
Utilities (electric power, natural gas, telephone)

 Table 2.2 is a list of basic industries that produce goods, together with examples of companies that are members of these industries. The companies represented in this table can be divided into two types, depending on the nature of their production operations. The two types are the manufacturing industries and the process industries. Manufacturing companies are typically identified with discrete-item production: cars, computers, machine tools, and the components that go into these products. The process industries are rep resented by chemicals and plastics, petroleum products, food processing, soaps, steel, and cement. Our focus in this book is on manufacturing.
There are other ways to classify companies. One altemative is to place a company
into one of three categories: -

1. Basic producer
2. Converter
3. Fabricator

TABLE 2.2 Basic Industries: Manufacturing and Process Industries

    Basic industry                              Representative company
    Aerospace                                   Boeing Co
    Automotive                                 General Motors
    Beverages                                   Coca-Cola
    Building materials                        U.S. Gypsum
    Cement                                       Lone Star Industries
    Chemicals                                   E.I. du Pont
    ClothingHanes Corp.
    Drugs, soaps, cosmetics               Proctor & Gamble
    Equipment and machinery
        Agricultural                              Deere
        Construction                           Caterpillar Tractor
        Electrical                                 General Electric
        Electronics                              Hewlett-Packard
        Household appliances              Maytag
        Industrial                                 Ingersoll-Rand
        Machine tools                         Cincinnati Milacmn
        Office equipment, computers   IBM
       Railroad equipment                  Pullman
       Steam generating                      Combustion Engineering
    Foods
       Canned foods                          Green Giant
       Dairy products                        Borden
       MeatsOscar                            Mayer
       Packaged foods                      General Mills
    Hospital supplies                        American Hospital Supply
    Metals
       Aluminum                              Alcoa
       Copper                                  Kennecott
       Steel                                     U.S. Steel
    Natural resources
       Coal                                     Pinston
       Forest                                  Georgia-Pacilic
       Oil                                        Exxon
    Paper                                       Kimberly Clark
    Textiles                                    Burlington Industries
    Tire and rubber                         Goodyear

The three types form a connecting chain in the transformation of natural resources and basic raw materials into goods for the consuming public. The basic producers take the natural resources and transfonn these into the raw materials used by other industrial manufacturing firms. For example, steel producers transform iron ore into steel ingots.
The converter represents the intermediate link in the chain. The converter takes the output of the basic producer and transforms these raw materials into various industrial products and some consumer items. For example, the steel ingot is converted into bar stock or sheet metal. Chemical finns transform petroleum products into plastics for molding. Paper mills convert wood pulp into paper. A distinguishing characteristic of the convener is that its products are uncomplicated in physical form. The products are not assembled items. The production processes used to make the products may be complex but the products themselves are not.
The third category of manufacturing firms is the fuhricator. These firms fabricate and assemble final products. The bar stock and sheet metal are transformed into machinedengine components and automobile body panels. The plastics are molded into various shapes. Then these parts are assembled into final products, such as tmcks, automobiles, appliances, garments, and machine tools. Fabricators include both the firms that produce the components and those which assemble the components into consumer goods.
There are several complicating factors in this classification. Some firms possess a high degree of vertical integration, which means that their operations include all three categories. The major oil firms are examples of vertical integration. They convert natural resources into finished petroleum products and then market these products directly to the consumer. Another complicating factor is that some companies-the conglomerates-are in so many different types of business that it is difficult to classify them. Some of their operations are in the basic producer category; others are converters; and still other lines of business fall into the fabricator category.

REFERENCES

[1] BUCKINGHAM, W., Automation, Harper & Row, Publishers, Inc., New York, 1961.
[2] DRUCKER, P. F., "Automation Payoffs Are Real," The WallS1r¢¢t Journal, September 20 1985.
[3] Groover, M. P. and J. C. WlGINTON, “CIM and the Flexible Automated Factory of the Future," Industrial Engineering, January 1986, pp. 74-85.
[4] Groover, M. P., M. WEISS, R. N. NAGEL., and N. G. ODREY, lndustrial Robotics.Technology, Programming, and Applications, McGraw-Hill Book Company, New York, 1986 Chapter I.
[5] HARRINGTON J., Compuler Integrated Manufacturing, Industrial Press. Inc., New York 1973.
[6] LUKE, H. D. Automation for  Productivity, John Wiley & Sons, Inc., New York. 1972.
[7] MERCHANT, M. E., "The lnexorable Push for Automated Production." Production Engineering, January 1977, pp. 44-49.
[8] SILBERMAN, C. E., and the Editors of Forlune, The Myths of Automation, Harper & Row, Publishers, lnc., New York, I966.
[9} TERBORGH. G., The Automaton Hysteria, W. W. Norton & Company, Inc., New York 1966.

1.4 ORGANIZATION OF THE BOOK

The following 26 chapters of this book are organized into nine parts. This introductory chapter has attempted to set the stage and whet the reader's appetite for the technical chapters that follow on automation, production systems, and computer integrated manufacturing.

Part I contains two chapters, the first of which covers some of the fundamental concepts and principles of manufacturing and automation. The second chapter in Part I discusses production economics, an essential subject for justifying an automation project.
Part ll is concemed with high-volume production of discrete products. The type of automation used here is sometimes called "Detroit automation" because of its extensive applications in the automobile industry. The four chapters in Part ll discuss the production lines, both automated and manually operated, that perform processing and assembly operations. The automated production lines are examples of fixed automation.
Pan III covers numerical control, an example of programmable automation. Numerical control is used for batch production of parts and products. The program is formed out of numbers, hence the name numerical control. An extension of numerical control technology is industrial robotics.

Part IV provides three chapters on industrial robotics: its technology, programming, and applications. '
Part V deals with material handling, one of the physical activities in the factory that “touch” the product. We concentrate, of course, on automated systems. The two chapters in Part V discuss automated material handling systems and automated storage systems.
Part VI is concemed with group technology and flexible manufacturing systems. A flexible manufacturing system (FMS) is a representative application of flexible automation. Group technology is considered a necessary principle to achieving a successful FMS.
Part VII contains only one chapter-on quality control and automated inspection.Please do not interpret the one chapter as meaning that quality control (QC) is not important. The chapter is substantial, both in length and importance. We leam that automated inspection methods do not always have to “touch” the product.
Part VIII covers automatic control systems. We survey the traditional linear feedback control theory and then proceed to consider how computer systems are used to achieve control over manufacturing operations in a modem factory.
Finally,

Part IX presents an introduction to computer integrated manufacturing. The five chapters describe the elements of CIM: computer-aided design, computer-aided manufacturing, manufacturing planning, manufacturing control, and the glue that holds these computer systems together-computer networks. We conclude the book with a description of what the future automated factory will be like, and the social impact that it will have.

1.3 ARGUMENTS FOR AND AGAINST AUTOMATION

Since the time when production automation became a national issue in the late l950s and early 1960s, labor leaders and govemment officials have debated the pros and cons of automation technology. Even business leaders, who generally see themselves as advocates of technological progress, have on occasion questioned whether automation was really worth its high investment cost. There have been arguments to limit the rate at which new production technology should be introduced into industrv. By contrast, there have been proposals that goverment (federal and state) should not only encourage the introduction of new automation, but should actually finance a portion of its cost. (The Japanese govemment does it.) ln this section we discuss some of these arguments for and against automation.

Arguments against automation
First, the arguments against automation include the following :

1. Automation will result in the subjugation of the human being by a machine. This is really an argument over whether workers` jobs will be downgraded or upgraded by automation. On the one hand. automation tends to transfer the skill required to perform work from human operators to machines. ln so doing, it reduces the need for skilled labor. The manual work left by automation requires lower skill levels and tends to involve rather menial tasks (e.g., loading and unloading workparts, changing tools, removing chips. etc.). ln this sense. automation tends to downgrade factory work. On the other hand, the routine monotonous tasks are the easiest to automate, and are therefore the first jobs to be automated. Fewer workers are thus needed in these jobs. Tasks requiring judgment and skill are more difficult to automate. The net result is that the overall level of manufacturing labor will be upgraded, not down graded.
2. There will be a reduction in the labor force, with resulting unemployment. lt is logical to argue that the immediate effect of automation will be to reduce the need for human labor, thus displacing workers. Because automation will increase productivity by a substantial margin, the creation of new jobs will not occur fast enough to take up the slack of displaced workers. As a consequence, unemployment rates will accelerate.
3. Automation will reduce purchasing power. This follows from argument 2. As machines replace workers and these workers join the unemployment ranks, they will not receive the wages necessary to buy the products brought by automation. Markets will become saturated with products that people cannot afford to purchase. Inventories will grow. Production will stop. Unemployment will reach epidemic proportions. And the result will be a massive economic depression.

Arguments in favor of automation

Some of the arguments against automation are perhaps overstated. The same can be said of some of the declarations that advocate the new manufacturing technologies. The following is a sampling of the arguments for automation :

1. Automation is the key to the shorter workweek. 'I`here has been and is a trend towand fewer working hours and more leisure time. (College engineering professors seem excluded from this trend). Around the turn of the century, the average workweek was about 70 hours per week. The standard is currently 40 hours (although many in the labor force work overtime). The argument holds that automation will allow the average number of working hours per week to continue to decline, thereby allowing greater leisure hours and a higher quality of life.
2. Automation brings safer working conditions for the worker. Since there is less direct physical participation by the worker in the production process, there is less chance of personal injury to the worker.
3. Automated production results in lower prices and better products. lt has been estimated that the cost to machine one unit of product by conventional general-purpose machine tools requiring human operators may be 100 times the cost of manufacturing the same unit using automated mass-production techniques. Examples abound. The machining of an automobile engine block by transfer line techniques (discussed in Chapter 4 and 5) may cost $25 to $35. lf conventional techniques were used on reduced quantities (and the quantities would indeed be much lower if conventional methods were used) the cost would increase to around S3000. The electronics industry offers many examples of improvements in manufacturing technology that have significantly reduced costs while increasing product value (e.g., color TV sets, stereo equipment, hand-held calculators, and computers).
4. The growth of the automation industry will itself provide employment opportunities. This has been especially tnre in the computer industry. As the companies in this industry have grown (IBM, Burroughs, Digital Equipment Corp., Honeywell, etc.), new jobs have been created. These new jobs include not only workers directly employed by these companies, but also computer programmers, systems engineers, and others needed to use and operate the computers.
5. Automation is the only means of increasing our standard of living. Only through productivity increases brought about by new automated methods of production will we beable to advance our standard of living. Granting wage increases without a commensurate increase in productivity will result in inflation. ln effect, this will reduce our standard of living. To afford a better society, we must increase productivity faster than we increase wages and salaries. Therefore, as this argument proposes, automation is a requirement to achieve the desired increase in productivity.

No comment is offered on the relative merits of these arguments for and against automation. This book is concemed principally with the technical and engineering aspects of automated production systems. lncluded within the engineering analysis is, of course, consideration of the economic factors that determine the feasibility of an automation project.

1.2 REASONS FOR AUTOMATING

Companies undertake projects in automation and CIM for a variety of good reasons. Some of the important reasons for automating include the following :

1. Increased productivity. Automation of manufacturing operations holds the promise of increasing the productivity of labor. This means greater output per hour of labor input. Higher production rates (output per hour) are achieved with automation than with the corresponding manual operations.
2. High cost of labor. The trend in the industrialized societies of the world has been toward ever-increasing labor costs. As a result, higher investment in automated equipment has become economically justifiable to replace manual operations. The high cost of labor is forcing business leaders to substitute machines for human labor. Because machines can produce at higher rates of output, the use of automation results in a lower cost per unit of product.
3. Labor shortages. ln many advanced nations there has been a general shortage of labor. West Germany, for example, has been forced to import labor to augment its own labor supply. Labor shortages also stimulate the development of automation as a substitute for labor.
4. Trend of labor toward the service sector. This trend has been especially prevalent in the United States. At this writing (1986), the proportion of the work force employed in manufacturing stands at about 20%. ln 1947, this percentage was 30%. By the year 20()0, some estimates put the figure as low as 2% [7]*. Certainly, automation of production jobs has caused some of this shift. However, there are also social and institutional forces that are responsible for the trend. The growth of govemment employment at the federal, state, and local levels has consumed a certain share of the labor market which might otherwise have gone into manufacturing. Also, there has been a tendency for people to view factory work as tedious, demeaning, and dirty. This view has caused them to seek employment in the service sector of the\economy (govemment, insurance, personal services, legal, sales, etc.).
5. Safety. By automating the operation and transferring the operator from an active participation to a supervisory role. work is made safer. The safety and physical well-being of the worker has become a national objective with the enactment of the Occupational Safety and Health Act of 1970 (OSHA). lt has also provided an impetus for automation.
6. High cost of raw materials. The high cost of raw materials in manufacturing results in the need for greater efficiency in using these materials. The reduction of scrap is one of the benefits of automation.
7. Improved product quality. Automated operations not only produce parts at faster rates than do their manual counterparts, but they produce parts with greater consistency and conformity to quality specifications.
8. Reduced manufacturing lead time. For reasons that we shall examine in subsequent chapters, automation allows the manufacturer to reduce the time between customer order and product delivery. This gives the manufacturer a competitive advantage in promoting good customer service
9. Reduction of in-process inventory. Holding large inventories of work-in-process represents a significant cost to the manufacturer because it ties up capital. ln~process inventory is of no value. lt serves none of the purposes of raw materials stock or finished product inventory. Accordingly, it is to the manufacturer`s advantage to reduce work-in-progress to a minimum. Automation tends to accomplish this goal by reducing the time a workpart spends in the factory.
10. High cost of not automating. A significant competitive advantage is gained by automating a manufacturing plant. The advantage cannot easily be demonstrated on a company‘s project authorization form. The benefits of automation often show up in intangible and unexpected ways, such as improved quality, higher sales, better labor relations, and better company image. Companies that do not automate are likely to find themselves at a competitive disadvantage with their customers, their employees, and the general public.

All of these fastors act together to make production automation a feasible and attractive altemative to manual methods of manufacture.

* Numbers in brackets refer to the References at the end of the chapter.

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.