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Thermo-Electrical Non-Traditional Machining Operations and Machine Tools
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
Precision engineering is a term that is used to describe manufacturing of high-quality parts with close tolerances and good surface finishes. Based on their process capabilities, make a comprehensive list of non-traditional machining processes (NTMPs) with decreasing order of quality of parts produced. Include a brief commentary on each method.
Materials Selection in Precision Mechanics
Published in Richard Leach, Stuart T. Smith, Basics of Precision Engineering, 2017
The ceramics of most interest for precision engineering tend to be oxides, nitrides or carbides of aluminium, silicon or a few other elements. Figure 12.10 shows a property group profile typical of an oxide ceramic, in this case alumina (oxide ceramics tend to be identified by an ‘a’ or ‘ia’ ending). It is quite similar to, on average a little better than, the model material across the mechanical groups and not bad thermally except in groups that involve its low thermal conductivity. Zirconia is another common engineering ceramic, offering higher strength but otherwise tending to be inferior to alumina across the property groups used here (see Figure 12.11), implying that it would only occasionally be preferred for precision applications. Ceramics are electrical insulators that are perhaps still seen as applied mostly to small, often intricate, components. However, they have been applied very successfully to large loop structures, even as machine tool beds since at least the 1980s (Ueno 1989); the design rules are, of course, different to those for cast iron or steel.
Materials Selection in Precision Mechanical Design
Published in S.T. Smith, D.G. Chetwynd, Foundations of Ultraprecision Mechanism Design, 2017
The tables include a range of pure metals and alloys, but show few surprises. The common machine-shop metals, steels, aluminium alloys and brasses, are much used as structural materials in precision engineering. With the exception of the strength of hard steels they are generally indifferent performers across the whole range of groupings. They are used because high performance is not always needed, they are readily available and have low costs for materials or manufacturability. It is mildly surprising that neither aluminium nor copper alloys give good overall thermal performance, largely because of their high expansivity. The low density of aluminium is sometimes useful. The copper alloys also have rather high densities. However they are easy to work and still find a major role when non-magnetic structures are wanted. Bronzes and, particularly, beryllium copper perform well in the category most associated with spring design, Y/E, with other properties at best moderate for most precision applications of springs. Their common use for this purpose perhaps reflects both the unacceptability of steels (magnetic fields and corrosion may reduce repeatability) and the ease of providing thin sheets for ligament systems, for which the requirements are rather different to those for energy-storing spring applications. With careful heat treatment, hard beryllium copper may have a very finely distributed precipitate that rapidly arrests the motion under stress of crystal dislocations so that it makes very repeatable flexure hinges. This illustrates the limitation of numerically based selection methods, for it is difficult to quantify and tabulate such a property. Steel and cast iron, which also offers usefully high damping, still dominate for larger structures such as machine tools. Further details on thermal properties are given by Gitlin, 1955a.
Polynomial-based Stability Analysis of Modified IMC-PID Controller for Piezoelectric Actuator System in Time Delay Environment
Published in IETE Journal of Research, 2021
Sandip Jana, Saikat Kumar Shome, Arpita Mukherjee
Piezoelectric actuators are a class of flagship actuators being used in numerous micro/nano-manipulation-related industrial applications such as biological cell operator, precision engineering in PCB industry, MEMS manufacturing, space optics, etc. due to prominent advantages like precision positioning, speed of response, resistance to electromagnetic interference and high force capability [1–4]. The noise-less drive feature also make piezo actuators well suited for auto-focusing mechanisms in space telescopes and mobile phone imaging. Besides, as these actuators do not require lubrication, they can also be used at cryogenic temperatures in vacuum environment. However, uncertain nonlinear factors lead to a major bottleneck in exploiting the promising advantages of these actuators, and often lead to serious degradation of control performance [5,6]. Amongst the uncertain nonlinearities, hysteresis is the most challenging and several researches have been carried out on mitigating the effect of it. Creep and vibration have also been reported to have adverse effect on the precision positioning of piezoelectric actuators. The time lag brought about by the system response and latency induced therein due to hardware components of controllers also effects control aspects. A polynomial-based fractional order disturbance model for piezo electric actuator is proposed in [7] where piezo electric hysteresis can be significantly neglected over a wide bandwidth range.