Micro Manufacturing In The Classroom And Laboratory

The products that occupy the attention of manufacturing engineers can be separated, in one context, into three categories, determined by geometric dimensions: ordinary or customary; very small; very large. The engineering challenges of manufacturing parts in customary dimensions have migrated, in large part, from the technological into the arena of lean thinking. The technological frontiers of manufacturing, in the early portion of the 21 st century, lie in the very small and the very large. It is arguable that manufacturing in the very large is a mostly straight-forward extension of how we make parts of ordinary size, albeit with significant challenges of scale and rate. In the microand nano-realms, however, the technology is most-definitely-not a simple extension of the well-known. Here, the governing physics are different, new or vastly modified processes are required, and fixturing, gauging and assembly demand completely different approaches. Innovation rules. And applications of products centered on microand nano-technologies are now the fastest-growing segment of commerce. Hundreds of nano-enabled new products appear every year. Thus, one of the critical challenges of manufacturing engineering education is to devise means of introducing knowledge of processes and production for fabrication at microand nano-dimensions. This paper opens with a brief summary of sub-millimeter and sub-micron manufacturing and assembly processes, both in research laboratory and in factory. Then, an assessment of micro-machining processes is presented, paired with representative applications. The paper concludes with an outline and critique of a new course in mechanical micromachining initiated by the author. A View of the Landscape of Manufacturing Technology: New technology in manufacturing is migrating to the very large and the very small. Technological innovations are essential for manufacturing companies to maintain a competitive edge with aggressive firms in Europe, Asia and, increasingly, Latin America. While there remains much mileage in lean enterprise methodologies, those methods essentially address existing and mature manufacturing technologies. The lean mantra concentrates attention on more effective utilization of existing and established manufacturing technologies. Technological innovation is, typically, incremental, rather than dramatic. Established manufacturing technologies are available to anyone. Factories anywhere in the world can acquire even the most advanced machine tools based on mature technologies. The principles and practices of lean thinking are published in enormous variety. Pursuing this logic, it is postulated that continuing global competitiveness in manufacturing must also embrace innovation at a fundamental technological level. Such innovation depends on relentless pursuit of the new in manufacturing technologies and engineering. Perhaps most prominent among the current opportunities for innovation in manufacturing processing are those at the very small dimensional scale. Applications of micro-manufacturing are exploding. The flow of new products with dimensions shrunk to sub-millimeter size has become a torrent in medical device, automotive, portable energy, electronics, sensors and other industries. The manufacturing processes supporting this product flood contain significant differences from traditional macro-dimensioned processing. When workpiece dimensions shrink to millimeter-size and less, tool-workpiece interactions change. The micro-world follows a different set of rules from the macro-world. A Summary of Micro-Manufacturing: An examination of micro-manufacturing begins with a familiar categorization procedure. Much as in the conventional environment, processes can be categorized as ‘parts fabrication’ or ‘assembly’. While there are some processes that combine both functions, the distinction serves a useful taxonomic purpose. Up to the present time, fabrication of sub-millimeter parts has been enabled principally through migration of processes from microelectronics. Deposition-and-removal lithographic processes familiar in micro-circuitry manufacture have been employed for production of microelectro-mechanical systems (MEMS) with some notable success. Likewise, applications of such processes as ion beam implantation and chemical vapor deposition are being researched for nonelectronic products. MEMS devices and similar products have so far been, typically, created from monolithic pieces of silicon, relying on the very small dimensions to provide for flexing of components when functionally necessary. The market for sub-millimeter products is, however, expanding rapidly, and demand for more complex, multi-component products is beginning to emerge. Clear examples are found in medical devices. Products comprised of sub-millimeter parts for have been emerging steadily, for example, for orthopedic, cardiac and eye surgery and for low-invasive medical diagnostics. Further, complex micro-sensors are at the forefoot of an enormous wave of application. Very small transportable energy devices are beginning to proliferate. The list is both broad and deep. Frequently, these products are more amenable to manufacture by extrapolation of machining technologies, than by adaptation of lithographic techniques. [1,2,3] The terms ‘nano’, ‘micro’ and ‘meso’ are frequently employed to describe the small world of manufacture. These terms are rather imprecise, and there is no universal agreement as to where one realm stops and another begins. Some writers also employ the term ‘miniature’ in the spectrum.[3] We describe our work at North Dakota State as being with products generally in the miniature and meso realms according to the spectrum suggested in Figure 1. Part features, however, are usually in the meso and micro realms. When working in micro-milling or microforming, for example, we might develop processing methods for an article up to perhaps 2 to 3 millimeters in overall outer dimension that will have part features dimensioned down to, say, 40 microns. When working in deposition processing, the part features are generally in the 10 to 500 micron range. Figure 1: A dimensional spectrum for small-scale part manufacturing Assembling of micro-components has also received important research attention, and several methods have been defined. In general, micro-assembly can be differentiated as either serial or parallel, or alternatively, as deterministic or stochastic.[4] Serial, deterministic assembly can be seen as an extension of robotic techniques to the sub-millimeter world.[5] Figure 2: A taxonomy of micro-assembly techniques [4] Feature Size Miniature Meso 5 mm 1 mm 100 μ 1 μ 50 nm