Unit Manufacturing Processes: Issues and Opportunities in Research (1995)

The committee examined the many research opportunities that were identified within each family of unit processes in Part II to determine which were the most important to the advancement of unit process technology. The Unit Manufacturing Process Research Committee concluded that the efficacy of a new unit process, or process improvement, could only be assessed in the context of a specific application, although criteria could be developed to identify promising research opportunities. This led the committee to synthesize the various research opportunities identified for each family of unit processes. The common ones, known as enabling technologies, were those that underpin and enable a wide variety of unit processes, and thus their advancement would benefit multiple unit processes. As a result of the committee's analysis, these six technologies were found to be critically important:

• material behavior;
• simulation and modeling;
• sensors;
• process control;
• process precision and metrology; and
• equipment design.

Each of these technologies is discussed in a separate chapter that summarizes the current general research status and recommends research opportunities that would be key elements in securing the long-term competitiveness of U.S. manufacturing. Research in these enabling technologies must be connected to the basic physics of processes, and the results verified through experiments on specific unit processes.

Chapter 9 deals with the first enabling technology, the characterization of material behavior. This technology involves understanding the relevant material properties and microstructure that exist at the start of a unit process and how

they change in response to the processing. The evolution of microstructure, conditions under which fracture occurs, and an understanding of the role of interface conditions such as friction are among the elements that must be understood. A major issue is the enormous variety of materials that need to be studied, as well as the large number of parameters required to specify the behavior of each material.

Chapter 10 provides an overview of simulation and modeling technology. Simulation and modeling can oftentimes eliminate time-consuming and expensive trial-and-error process development and lead to rapid development of processes for new materials and new products. Impressive progress has been made in recent years in the numerical representation and solution of modeling process behavior. Improved understanding of material behavior is a prerequisite to more-precise numerical simulation of processes.

The next two enabling technologies, sensors and process control, are closely interwoven. Chapter 11 considers sensor technologies that 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 application needs to control the operation of unit processes monitor and diagnose equipment condition and to inspect and measure the product. Unit processes of the future are expected to be heavily dependent on advances in sensor technology.

Chapter 12 covers process control. The incorporation of improved computer software and hardware can make unit processes more flexible and adaptable while maintaining optimum operation of the process equipment. In the past, the predominant control methodology was the "black box" approach, which employed a simple invariant description of the unit process. Improved control algorithms, controller hardware, and sensors offer significant opportunities to advance process control.

The last two enabling technologies, process precision and metrology and equipment design, are closely linked to one another but also depend on the other four enabling technologies. Chapter 13 addresses the vitally important area of process precision and metrology. Effective product design and manufacturing hinge, in part, on matching process capabilities to part specifications and on applying measurement methods that support inspection and process control. As activity progresses from nominal design to final manufacture, the control of variability becomes the central issue.

Chapter 14 discusses process equipment design, which is the broadest and most critical of all the enabling technologies. This technology must be a critical focus of any unit process that will be commercialized. The equipment and associated tooling must be designed to fulfill a specific function in a production environment. Unit process equipment should be viewed as a platform for advanced sensors and control systems. Furthermore, practical considerations such

as costs associated with the purchase, installation, and maintenance of the equipment must be competitive with those of alternative processing equipment. Despite their extreme importance, academic teaching and research in the area of processing equipment and machine tools are just about nonexistent in the United States. This area needs increased emphasis and support, not only in research but also in terms of establishing new faculty positions and new academic programs.

Technologies that underpin and enable a wide variety of unit processes are critically important. Within this category, 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. Currently, advanced unit processes are not utilizing recent developments in control theory to the extent possible.
• Materials behavior research aimed at providing information that can be used 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 processes in ways useful to both design engineers and process planners. These models should provide for the organization and codification of disparate process precision and metrology information. They should support methods for assessment of scalability of precision levels and intrinsic precision.
• Methodology and practice for process equipment (e.g., machine tools) and process modeling design. The engineering design of process equipment should be developed into a special engineering practice with the necessary supporting analysis tools, since it requires the integration of many other supporting technologies.