American companies must be able to manufacture products of superior quality at competitive costs to compete effectively in the global economy. Many studies undertaken in recent years to define the most important areas of industrial research have emphasized the need to place manufacturing process development on an equal basis with new product technologies. According to these studies, the United States must establish a preeminent foundation in engineering and science, which is capable of innovating and improving not only products but manufacturing processes.
Investment in manufacturing is commonly measured by the amount of capital equipment that is purchased. This approach does not incorporate the investment in the underlying infrastructure, which includes the development of process technologies and the education and training of a motivated work force. Future economic success will be driven not only by capital spending but by process technologies and the skill base of the work force.
This report suggests key criteria for determining the critical elements of unit processes and applies these criteria to illustrative examples to demonstrate how the criteria can be used to identify opportunities in research and development (R&D) for unit process technologies and the supporting enabling technologies. Generalized conclusions and recommendations regarding process technologies are presented that support a strategy of improving national competitiveness in manufacturing.
Fundamentals Of Unit Manufacturing Processes
Manufacturing, reduced to its simplest form, involves the controlled application of energy to convert raw materials (typically supplied in simple or shapeless forms) into finished products with defined shape, structure, and properties. Usually manufacturing entails the sequencing of the product-forms through a number of different processes. Each individual step is known as a ''unit manufacturing process.'' For the sake of brevity, the committee will refer to them
as "unit processes." These unit processes can be considered as the fundamental building blocks of a nation's manufacturing capability.
There is an extraordinarily large number of unit processes. However, many share common traits that can be used as the basis for organizing them into families. The committee chose a taxonomy for this study based on the physical process by which the configuration or structure of a material is changed. In order to narrow the scope of this study, the committee excluded consideration of the following types of unit processes: production of raw materials, alloy development, chemical synthesis, fabrication of electronic materials, component assembly, and information technology. Taking these exclusions into consideration, five distinct unit process families were rationalized:
mass-change processes, which remove or add material by mechanical, electrical, or chemical means (included are the traditional processes of machining, grinding, and plating, as well as such nontraditional processes as electrodischarge and electrochemical machining);
phase-change processes, which produce a solid part from material originally in the liquid or vapor phase (typical examples are the casting of metals, the manufacture of composites by infiltration, and injection molding of polymers);
structure-change processes, which alter the microstructure of a workpiece, either throughout its bulk or in a localized area such as its surface (heat treatment and surface hardening are typical processes within this family; the family also encompasses phase changes in the solid state, such as precipitation hardening);
deformation processes, which alter the shape of a solid workpiece without changing its mass or composition (classical bulk-forming metalworking processes of rolling and forging are in this category, as are sheet-forming processes such as deep drawing and ironing); and
consolidation processes, which combine materials such as particles, filaments, or solid sections to form a solid part or component (powder metallurgy, ceramic molding, and polymer-matrix composite pressing are examples, as are joining processes, such as welding and brazing).
Even though these unit processes are very diverse, they all possess five key process components: the workpiece material, process tooling, a localized workzone within the material, an interface between the tooling and the workzone, and the process equipment that provides the controlled application of energy. Advances in unit process technologies can be targeted at any one, or all, of these components, although usually all five are affected to some extent by a change in
any one of the components. Thus, a systems approach is required for improving existing unit manufacturing unit processes and for developing new ones.
This taxonomy of unit processes is independent of the type of material being worked. Specific material considerations are taken into account through understanding the mechanisms that occur in the workzone. The overall organization of unit processes can be conceptualized in three-dimensional space with one axis being the unit process families; the second axis, the unit process components; and the third axis, the types and combinations of materials being processed.
Setting Priorities For Unit Manufacturing Processes
The overall significance of a unit process innovation can be determined from several primary considerations:
Does it offer the potential to be cost-effective? This factor examines, from basic considerations, the ability of a process to provide the required quality level at minimum input cost per unit of output. This would include, for example, the minimization of such factors as energy use, scrap generation, and labor costs. Thus, a single precisely controlled process that combines in essentially one operation what had previously required multiple operations could be highly rated by this criterion.
Does it provide a unique way to cost-effectively exploit the physical properties of an advanced material? Too often, advanced materials with outstanding properties have languished in the laboratory because little, if any, consideration has been given to the methods required to produce them in usable shapes and quantities. Processes that are fundamentally simple, requiring low capital investment, would be highly rated by this criterion.
Can it shorten the time to move a product technology from the research stage to commercialization? This factor includes the capability of providing rapid response to customer needs. Unit processes that are relatively easy to scale-up from the laboratory to the factory due to their inherent flexibility, as well as efforts to develop process technology concurrently with the product technology, would be highly rated.
Does it provide a method of processing that is fundamentally environmentally friendly? Since it is often difficult to attach a firm cost to environmental transgressions a priori, processes that avoid the difficulty in the first place, or that produce environmental effects that can be readily mitigated, would be highly rated.
Is it applicable to a diverse range of materials? This criterion would rate higher those processes that are adaptable to a range of materials, and those that are more specialized would rate lower. However, it should be noted that nearly every unit process requires some amount of adjustment to accommodate different types of materials.
The committee selected several examples of unit processes from each of the five families and developed recommendations for research opportunities by applying the above criteria. These specific recommendations are representative of how priorities in unit process R&D can be established within a defined context, but they are not all inclusive.
The committee determined that the following six areas of applied scientific and technical knowledge are intrinsic to the design and operation of nearly every unit process and therefore may be termed "enabling." These areas, called "enabling technologies" here, provide primary levers of change in unit manufacturing processing.
Understanding Material Behavior
This technology involves understanding the relevant material properties and microstructure that exist at the start of the process and how they change in response to the processing. The evolution of microstructure, conditions under which fracture occurs, and the role of interface conditions such as friction and heat transfer are among the elements that must be understood. Furthermore, these elements should be known at various levels of scale. For example, shape changes resulting from deformation processes can be readily treated at a macroscopic level, but understanding the origins of crystallographic texture in a highly worked product requires knowledge of properties at a microscopic level. It is often convenient to represent process criteria and mapping of defects and damage in terms of process parameters, in a format known as "process maps." This may entail the development of databases that are useful in characterizing material behavior under extreme conditions (e.g., high temperature, high strain rate).
Use Of Simulation And Modeling
This technology includes the analytical and numerical representation of the five components of a unit process. Simulation and modeling can often eliminate time-consuming and expensive trial-and-error process development and lead to rapid development of processes for new materials and new products. Simulation of unit processes is largely based on computer-aided approaches and includes three main activities: modeling, visualization, and design. The essence of modeling involves solving the classic laws of conservation of mass, momentum, and energy for constitutive formulations of the material behavior during its residency in the unit process. The solution procedure is governed by initial and boundary conditions that represent the process conditions. The complexity of the model may be simplified with first-order assumptions to provide a solution with reasonable accuracy. This methodology goes far beyond the empirical techniques of the past. The most important task in unit process design is selecting the optimum processing conditions that will ensure the required mechanical and physical characteristics of the product at the necessary quality level. Experimental validation must accompany more-sophisticated modeling procedures.
Application Of Sensors
Sensors are independent devices that can measure process conditions and the response of the material. Sensor technologies play a critical role in the establishment of advanced process control architectures and the production of quality products. There are a wide range of sensor applications that could control the operation of unit processes, monitor and diagnose equipment condition, and inspect and measure the product. They may be remotely located, incorporated in the equipment, contained within the workpiece, or placed in the interface between the workpiece and the tooling. Sensors must not interfere with the process, and they must be robust enough to survive the processing environment. Sensors will be crucial for implementation of intelligent process control and in situ quality technology. Unit processes of the future are expected to be heavily dependent on advances in sensor technology.
Implementation Of Process Control
The incorporation of improved computer software and hardware can make unit processes more flexible and adaptive, while maintaining optimum operation of the process equipment. For example, recent advances in intelligent process
control methods make possible self-directed midcycle changes that are based on the response of the material to process variables. This ensures high-quality parts even if the initial and boundary conditions vary. In the past, the predominant control methodology employed the "black box" approach, which used a simple invariant description of the unit process, and advances in control theory were underutilized. Tools to design improved control algorithms and controller hardware are readily available and should be aggressively applied to developing advanced manufacturing process control.
Development Of Process-Related Precision And Measurement Technology
Effective product design and manufacturing hinge, in part, on matching process capabilities to part specifications and on applying real-time measurement methods that support inspection and process control. As activity progresses from initial design to final manufacture, the control of variability becomes the central issue. Variability arises from limitations in the control of the physical processes used to make and assemble parts, as well as from the tolerances inherent in the tooling and workpiece materials used in the processes. In the past, this area has received less attention from researchers than other technologies which, has restrained progress toward producing the highest-quality products cost-effectively.
Design Of Process Equipment
This technology must be a critical focus of any unit process that will be commercialized. Of all the enabling technologies, equipment design is necessarily the broadest, since it draws on all the other enabling technologies. The equipment and associated tooling must be designed to fulfill a specific function in a production environment. Unit process equipment should be viewed as platforms for advanced sensors and control technology. Furthermore, practical factors such as costs associated with the purchase, installation, and maintenance of the equipment must be competitive with alternative processing equipment. Other factors include process cycle time, robustness, maintenance, flexibility of use, production rates, and resultant part quality. This technology can be advanced by innovative designs, as well as by systematic incremental improvements.
Conclusions And Recommendations
- There are hundreds of unit manufacturing processes that exploit a very wide range of material modifying phenomena. Each process has some distinctive characteristics and parameters. Common sets of characteristics can be used to organize these processes into families. If such a taxonomy is constructed according to the physical process by which the configuration or structure of a material is changed, five process families result that specialize in processes that change mass, change phase, change structure, deform, or consolidate.
- When examined as an isolated entity, the criticality of a particular unit process to overall industrial success cannot be determined. It is only when the unit process is evaluated in the context of manufacturing specific products that an assessment of criticality of the unit process, and improvements that could result from suitable R&D, can be made. However, generic criteria can be developed to make relative assessments and to guide the allocation of R&D resources.
- The following criteria can be applied to evaluate projects in unit process R&D: How well does the project offer the inherent potential for cost-effective production and shaping of materials? Does it exploit the physical properties of an advanced material cost-effectively and in an unique way? Can it shorten the time needed to move a product technology from the research stage to commercialization? Does it provide a processing method that is inherently environmentally friendly? Is it applicable to a range of materials? Can it produce a variety of parts?
- There are six critical enabling technologies that serve as the foundation for unit process improvements: characterization of material behavior, simulation and modeling tools and technology, advanced sensor technology advanced process control technology process-related precision technology, and process equipment improvements. Research in these enabling technologies must be connected to the basic physics of processes, and the results must be verified through experiments on specific unit processes.
- There are opportunities for major and minor improvements across the whole spectrum; these range from advancements in specific unit processes to improvements in the underlying enabling technologies.
- The links between initial design and final manufacturing are often inadequate. Design engineers typically specify parts and products in terms of nominal shapes, materials properties, and part-mating relations with allowable variations (tolerances). Processes for making parts and products are usually specified by phenomenological parameters, for example, process temperatures, feed rates, and pressures. Thus there is a "mismatch" between the static parameters of design and the dynamic parameters of manufacturing processes.
- A science has not developed around most of the unit processes. This can be attributed to the fact that in most cases scientific principles from many different disciplines are involved (e.g., physics, chemistry, mechanics, electronics, and materials). No principles unique to unit processing have emerged that could serve as a unifying framework for a new science.
- Several high-level measures indicate that the United States may be underfunding both unit process R&D and education and training of the workforce. Particular care must be taken to direct available funding to the most promising opportunities and the most pressing educational needs.
- Even though this report primarily addresses the development of unit process technologies, the committee does not believe that process technologies alone will contribute to overall improvements in manufacturing competitiveness. The nation must possess an educated, motivated workforce, as well as industries committed to making appropriate investments in manufacturing facilities and equipment. Therefore, significant improvements in unit manufacturing process technologies will require, in addition to research in these technologies improvements in workforce education and industrial implementation.
- Technologies that underpin and enable a wide variety of unit processes are critically important. Research in these enabling technologies must be connected to the underlying physics of processes, and the results verified through experiments on specific unit processes. The following enabling technologies should receive the highest priority:
- Improved and innovative advanced sensor technologies that could be used to enhance unit process control and increase productivity . These sensors would be capable of real-time measurements of such quantities as geometric tolerances, material condition, and process conditions.
- Improved unit process control resulting from extending advanced control theory and concepts, such as self-tuning controllers that employ expert systems and embedded process models. These controllers would take full advantage of the real-time data provided by advanced sensors.
- Materials behavior research aimed at providing information usable by process simulation models. The vast amount of information already available needs to be collected, analyzed, and organized in a form usable by these models. The use of improved descriptions of material behavior in simulation should be validated with experimental data.
- Models for characterizing the precision of unit processing in ways useful to design engineers and process planners; methods for assessment in terms of scalability, intrinsic precision, and currently available precision; and the organization and codification of disparate process precision and metrology.
- Encourage universities to offer suitable courses specializing in the principles of tolerancing, metrology, and process modeling within the engineering and manufacturing disciplines.
- Encourage and strengthen the framework within which industry, government agencies federal and national laboratories, and universities can collaborate on research to improve the design of process equipment.
- Government agencies involved in sponsoring R&D in manufacturing processes (e.g., National Science Foundation, Department of Defense, Department of Energy, and National Institute for Standards and Technology) together should carefully evaluate the kinds of manufacturing R&D being supported and the relative funding levels for defense and nondefense R&D. This evaluation could also examine the extent to which other leading industrial countries, notably Germany and Japan, have been effective in commercializing unit process technology, given their investment in research that is related to manufacturing, which is considerably higher (as a proportion of their gross domestic product) than that of the United States.
- The committee recommends that incentives be found and implemented to increase the number of students majoring in manufacturing-related technology at universities, so that sufficient trained personnel are available to exploit research opportunities in unit processes and to guide their industrial implementation. For example, the National Science Foundation could convene a study group to determine appropriate educational incentives in the context of expected technical opportunities, industry needs, and employment opportunities. One incentive that would quickly attract high caliber students would be an
- increase in the number of fellowships available to those specializing in manufacturing.
This report is divided into four parts. Part I, "Fundamentals of Unit Manufacturing Processes," contains two chapters that discuss the importance of manufacturing and explain the basic definitions used throughout the report. Part II, "Research Opportunities in Illustrative Unit Manufacturing Processes," contains six chapters; each chapter is dedicated to a particular class of unit process. Part III, "Key Unit Manufacturing Process Enabling Technologies," also contains six chapters; each chapter in this section is devoted to a particular enabling technology. And Part IV, ''Policy Dimensions," contains three chapters that discuss issues in resource allocation for unit process R&D and education, and an overview of the experience of other industrialized countries in manufacturing-related R&D.