Process Equipment Design
Manufacturing equipment is the platform for the operation of unit processes. Properly designed equipment is essential for the production of high-quality, cost-effective products. Equipment design is necessarily the broadest category of the six enabling technologies, since it ultimately serves as the vehicle to implement all of the other enabling technologies. As pointed out in the introduction to this report (Chapter 1), the United States must be able to manufacture products of superior quality at competitive prices in order to maintain its standard of living and its standing in the world economy. The introduction also emphasized that competitiveness depends on new and improved processes and less on product technologies. Thus, the design of the equipment used in manufacturing processes assumes a dominant role in industrial competitiveness. This point was recently underscored by Eagar and Fine (1992):
The processing equipment industries play a unique role in an economy. They provide the tools for all the other manufacturing sectors in the economy. Even though education of the workforce, improved operations management, faster transportation, and communication have each increased productivity, in the long run, the influence of improved processing equipment almost certainly provides a multiplier which exceeds all of these other factors combined.
The importance of equipment design is clear to the technical community. Many recent articles have discussed topics such as robust design, design optimization, design for manufacturing, and doctoral programs in design. A recent text that presents a valuable discussion of the many factors involved in equipment design is Slocum's Precision Machine Design (Slocum, 1992). A case can be made for the importance to domestic manufacturers of high-quality, locally produced processing equipment rather than reliance on foreign suppliers.
There are many research needs for innovations in equipment design, since this area is necessarily broader than the other enabling technologies. Rapid speed of operation, high accuracy of positioning, high structural rigidity, flexibility of operation, user friendliness, and safety are highlighted below, because experience has indicated that improvements in these areas are highly desired and thus most likely to be incorporated if they are shown to be cost-effective (costs associated with the purchase, installation, and maintenance of new equipment must be competitive with existing alternatives). Specific details would depend, of course, on the specific unit process under consideration. The end result would be world-class unit process equipment available at a competitive sales price with low lifecycle costs.
However, the committee suggests that the greatest research need in the area of equipment design is the interaction of process equipment manufacturers with one another and with university research, national laboratories, and other government agencies to identify needs that are broader and more long-range than those the committee has identified for the other five enabling technologies or in this section on equipment design.
Two strategies have been employed to develop advanced unit process equipment—incremental and breakthrough. The incremental approach involves a systematic series of improvements to the equipment that address specific needs. It is a relatively low-risk approach, usually involving a multidisciplinary team of researchers. Over a period of time, significant advancements to existing unit process equipment can result.
Innovative, breakthrough design concepts, on the other hand, have the potential for dramatic improvements in unit process equipment. This a high-risk, high-payoff approach that rarely results from a systematic approach to equipment design. It is a contentious issue, but the committee's opinion is that the creative, innovative, or inventive aspect of design apparently does not lend itself to a rigorous description or systematic instruction. This strategy involves exposing a talented, creative individual to the problems and providing a stimulating environment in which ideas can flourish without a great number of constraints. These innovative ideas can then be further refined and developed with a systematic approach.
Efforts are needed to improve speed of operation. This topic includes fast movement of the equipment components during the unit process sequences with minimal dwell times during the unit process cycle. Examples of rapid operation speed in the machine tool area are the ultrahigh spindle speeds in milling and
turning centers. Additionally, providing minimal warm-up time from process start-up to operational steady state are critical to attaining rapid speed of operation and achieving consistency of part characteristics, such as dimensional control.
Efforts to provide highly reproducible, accurate positioning of production equipment component motions are needed to support the precision levels discussed in Chapter 13. Positional errors in processes lead to variations in product tolerances and quality. Errors in equipment motion locations, either on an absolute (based on one reference point) or incremental (based on sequential locations) base, often are additive in nature, with errors that are introduced early in the process sequence influencing positioning problems later in the unit process sequence (Tomizuka, 1989). The areas requiring emphasis are unit processes with multiple action sequences that possess several reference points that could be used for positioning.
Very rigid, stiff structural elements of unit process equipment are required, since these are primary factors determining positional accuracy and the level of precision inherent to the process.1 Required are innovative equipment designs that dampen vibrations (so that they are not transmitted to the tooling and workpiece), which originate from the process or external sources. For example, taking heavy machining cuts with nonideal coolant application and poor cutting tool conditions can result in self-induced ''chatter'' in the tooling and workpiece, often resulting in poor surface quality condition and dimensional variations in the machined part. Also, equipment designs that minimize thermal distortion due to nonuniform temperature variation that is caused by internal and external heat sources are needed so that the equipment can maintain positional accuracy during all phases of equipment operation.
Developing unit process equipment that can readily and rapidly change the operation format and tooling for a variety of parts is critical to the competitiveness of a unit process. Achieving short job-to-job setup times; flexible, versatile tooling and fixtures; and multiple process capability is important. Current trends in small-lot-size manufacturing place even greater emphasis on these aspects of equipment design.
The development and maintenance of the skill base needed to operate unit process equipment efficiently is a constant challenge in manufacturing. Equipment design should lend itself to efficient training of both operators and maintenance personnel. There are opportunities to improve the unit process
equipment design so that it is user friendly for the operation and maintenance aspects of the process. For example, designs that are compatible with control features, requiring minimal intervention during operation, are needed. Considerations that override all others are to develop equipment that is safe to operate and imposes no harmful effect on the workers or environment.
Eagar, T., and C. Fine. 1992. Does the drop in manufacturing employment mean we're less competitive? Leaders for Manufacturing Program Newsletter. Boston, Massachusetts: Massachusetts Institute of Technology.
Slocum, A.H. 1992. Precision Machine Design. Englewood Cliffs, New Jersey: Prentice Hall.
Tomizuka, M. 1989. Design of digital tracking controllers for manufacturing applications. American Society of Mechanical Engineers Manufacturing Review 2(2): 82-90.