Chapter 1 Introduction PDF

CHAPTER 1 INTRODUCTION  CHAPTER 1 INTRODUCTION The development of advanced information technologies in production has been, and will continue to be, the major technical driving force in manufacturing change. The electronics and informatio...

CHAPTER 1 INTRODUCTION  CHAPTER 1 INTRODUCTION The development of advanced information technologies in production has been, and will continue to be, the major technical driving force in manufacturing change. The electronics and information technologies provide new possibi1ities to produce a variety of products in an efficient way. Modern manufacturing is beginning to approach the flexibility of the classic job shop mode of production, but at a productivity level that is far higher. Indeed, productivity in flexible systems can now emulate with mass-production methods. Also it seems evident that the information technologies help to produce goods of superior quality. Yet the new production systems seem to function efficiently on a much smaller scale (machines and personnel) than the older mass- and large-series production systems. The introduction of computers into the manufacturing environment has revolutionized manufacturing technology. As computers have become more powerful with their increasing ability to perform complex calculations quickly and manage vast amounts of data, they have found their way into numerous manufacturing applications including part design and analysis, production scheduling and control, inventory and cost accounting, process control, and optimization and machinability data analysis. Time-sharing computer networks have brought the computer to design engineers, process planners, production control personnel and in many cases, out to the machine operators at the NC machine tools. The days when the computer was simply an accounting tool or a scientific tool are gone. Every phase of the production process has been affected, and the future promises that even more work will be taken over by the computer. This should hopefully lead to design engineers being more creative, manufacturing engineers tackling more problems, and products being better engineered and produced more efficiently. Why Is Greater Flexibility Needed Now? On one hand, there has always been a demand for customization of products, and for special niche products. However, this was not cost efficient unit recently because of technological constraints. So one can say that production was rigid and customers were necessarily flexible. The rapid development of information technologies has made it increasingly possible to combine efficiency and flexibility in a single productive unit. The customers can now be more inflexible about their desires, and production must become more flexible and adaptive. Thus, it can be argued from one perspective, at least, that industrial change is now mainly technology driven. The information technologies, in particular, provide new options. These promote a continuous search for competitive advantage and for ways to “take off” from the classic mass- production into a more competitive and beneficial environment. This means that, to gain benefits from information technologies, companies must look for new options. Previously, it was normal to make a single product, using specialized machinery and skills, and to market it more or less unchanged to many, global markets. Now it is necessary to make a variety of products using flexible machinery and multiskilled personnel, targeted to specific, segmented markets. The stated goals and targets of production automation such as flexibility, accuracy, processing speed and complexity of parts are really secondary. They are merely the tradeoff between economic benefits and costs of technological solutions. The main technological driving force has been the development of information technologies., i.e., semiconductors and basic electronics, computer technologies and software, and communication technologies. This development has been fundamental both for manufactured products and for the production technology of manufacturing industries. The customizing of products is not always a reaction to be the changed competitive environment. The flexibility needed to respond can also be used in an active way to create new market options and new competitive advantages. Computer integrated manufacturing (CIM) is a method or approach to integrate different functions (from market planning, product design, and production planning and control to manufacturing and distribution) by computers and information technologies. Automation systems are used not only to reduce direct labor costs, but also to cope with a changing business environment and to create new competitive advantages and options. Automation Defined Automation involves automatic handling between machines and continuous automatic processing at the machines. The elements continuous and automatic are necessary to separate automation from other production systems, such as mechanization. Automation exists only when a group of related operations are tied together mechanically, electronically, or with the assistance of computers. The word “automation” was coined at Ford Motor Company in 1945 to describe “a logical development” in technical progress where automatic handling between machines is combined with continuous processing at machines. This implies that combining two or more automatic operations on a standard machine (such as found with automatic bar machines, vertical turret lathes, and others) does not constitute an automated system. Machines are considered automated only when they are mechanically joined for continuous automatic handling and processing. If an automatic bar machine is connected mechanically to a material feed or to the conveyor that advances parts, it is called an automated system. Automation is a technology concerned 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 Part and Process Design A basic principle in automation is that the design of the part and the design of the process should be related as closely as possible. Close cooperation between product and equipment designers is essential, not only to avoid excessive costs in automated machines and to ensure maximum efficiency in processing but also to provide the highest degree of flexibility. Without some idea of what future changes may be made in a part, the equipment builder cannot provide for them. For example, the power source, the type of transfer equipment, and the orientation of parts need to be defined. 1. Power sources. The basic machine movements are linear, as in the travel of a drill or rotary, such as an indexing table. The power for these movements are electrical, pneumatic, or hydraulic. The selection of the power source depends on availability, relative cost, amount of power, space, and speed requirements. 2. Transfer equipment. Mechanical loading and transfer devices are used to move components of varied geometry from machine to machine. Special jaws grip the part, lift, move, and turn it on arms, and place it into the new work position. Travel distance, direction, sequence, and speed are controlled mechanically, electromechanically, or with fluidic controls. Robots and computer control are used. Dead stops, mechanical arms. or iron hands can be reprogrammed, but not very readily. However, robotic manipulators overcome the inflexibility of mechanical manipulators. 3. Parts orientation. A step in the assembly process is the orientation of parts. This work can be done by operators who will pick, orient, and place the part in another location. The parts may be jumbled from a previous operation or they may be stacked horizontally, vertically, in order, random, or arranged by size. The choice here is almost limitless. Parts orientation work is popular, especially in low-volume work, where direct labor employees arrange the parts. As volume increases, it pays to consider other ways. Numerous mechanical, pneumatic, vibratory, and ingenious devices exist to orient parts. In some systems, a robot or a part-feeding system is used to orient an individual part and present the component consistently for assembly. Parts are manually oriented either directly into a feeding system on the robot arm or into a magazine tray from which the robot removes them. In contrast, a computerized visual detection system can orient and present the part without the need for manual labor. Types of Automation Automated production systems can be classified into three basic types: 1. Fixed automation 2. Programmable automation 3. Flexible automation 1. Fixed Automation It 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. It 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:  Low flexibility (task and process fixed). Thus a dedicated assembly machine for product X will only perform the process of assembly, and will only be capable of the task of assembling product X; it could not assemble product Y.  Designed specifically to perform a dedicated task in a process, in the most efficient possible manner. Thus task performance is optimized at the expense of flexibility.  Comprises extensive custom mechanical tooling and mechanisms.  Long lead-time to implementation, due to specialist mechanisms.  Most economic for high-volume production, as all components of system are optimized for one task.  Will perform the task with the shortest cycle time of all types of automation.  Difficult/impossible to modify the task that the machine performs.  Most/all of the machine is redundant at the end of the task.  Examples: engine block machining transfer line, brush-making machine, dedicated assembly machine, newspaper printing machine, motor winding machine, vibratory parts feeders.  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 alternative 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). 2. Programmable Automation In this type, the production equipment is designed with the capability to change the sequence of operations to accommodate different product configurations. The program controls the operation sequence, which is a set of instructions coded so that the system can read and interpret them. New programs can he prepared and entered into the equipment to produce new products. Some of the features that characterize programmable automation include:  Intermediate flexibility — process fixed, task variable. Thus a CNC machine tool will only perform a machining process, but can carry out many different types of machining tasks via reprogramming.  Computer-controlled actuators and sensors are used to position mechanisms in place of hard stops.  Physical construction optimizes the performance of one type of process and prevents the performance of other processes.  Computer control enables reprogramming of tasks.  Examples: CNC machine tools, automatic guided vehicles, computer controlled pneumatic actuators.  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 1952) and industrial robots. 3. Flexible Automation It is an extension of programmable automation. The concept of flexible automation has developed only over the last 30 years, and the principles are still evolving. A flexible 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 hatches. The features of flexible automation can be summarized as follows:  High flexibility task and process variable.  Based on the use of industrial robots.  Mechanical mechanisms limited as robots provide the majority of manipulation.   Mechanical tooling mainly limited to robot grippers, workpiece holding, component supply and fixtures.  Lead-time dependent on amount of specialist tooling.  Physical construction does not limit process applications.  Can be programmed to modify the task.  The robots can be reused at the end of the task or process application.  Examples: robot welders, robot painters, robot assembly machines.  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 interrupt production on the current job. Advances in computer systems technology are largely responsible for this programming capability in flexible automation. Changing the physical setup between parts 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 parts and transfer into position at the workplace is one way of implementing this approach. For these approaches to be successful, the variety of parts that can be made on a flexible automated production system is usually more limited than a system controlled by programmable automation. The growing applications of computer systems in manufacturing are leading us toward the computer-automated factory of the future. 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. In 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. In 1986, the proportion of the work force employed in manufacturing stands at about 20%. In 1947, this percentage was 30%. By the year 2000, some estimates put the figure as low as 2%. 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 government 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 (government, 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). It 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. 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. In-process inventory is of no value. It 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 factors act together to make production automation a feasible and attractive alternative to manual methods of manufacture. Arguments for and Against Automation Since the time when production automation became a national issue in the early 1970s, labor leaders and government 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 industry. By contrast, there have been proposals that government should not only encourage the introduction of new automation, but should actually finance a portion of its cost. (The Japanese government does it). In 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 he downgraded or upgraded by automation. On the one hand, automation tends to transfer the skill required to perform work from human operators to machines. In 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 wonkparts. changing tools, removing chips, etc.). In 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 downgraded. 2. There will be a reduction in the labor force, with resulting unemployment. It 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. 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. There has been and is a trend toward fewer working hours and more leisure time. (College engineering professors seem excluded front 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. It 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. The machining of an automobile engine block by transfer line techniques may cost $25 to $35. If 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 $3000. 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 true in the computer industry. As the companies in this industry have grown 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 be able to advance our standard of living. Granting wage increases without a commensurate increase in productivity will result in inflation. In 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. In this course, we are concerned principally with the technical and engineering aspects of automated production systems. Included within the engineering analysis is, of course, consideration of the economic factors that determine the feasibility of an automation project. Applications of Automation Technology Nearly all human endeavors, including education, recreation, health care, national defense, communication, transportation, industrial manufacturing and processing, research and development, and business and commerce have been impacted by automation.