Technology suitable for both serial and small quantity production
Microturning is a method for producing micropins, but it is more difficult to realize other applications. The reason for this is the deformation of the workpiece. This is similar to the case of the microendmilling, however the workpiece in micro turning is often more elastic than the tool in microendmilling. Diameters larger than 100 µm is the practically applicable range in case of microturning. It is possible to fabricate another kind of microparts using conventional ultraprecision turning. After cutting microsteps on the surface of a plate, microparts can be cut out by other methods such as WEDM or grinding. As a result, microparts with microsteps can be fabricated.
Diamond turning is a cutting process capable to obtain an absolute accuracy better than 1 µm and 0.002~0.005 µm Ra in some metals. Its application is the production of mirror surfaces in optical quality components, moulds or reference parts. Tool geometry must be accurate, being the control of the edge radius and the tool tip radius the key parameters to obtain mirror finishing. The control must be performed with an accuracy of 3~75 nm, natural and synthetic diamond tools are usually applied. Diamond at high temperature reacts with those metals that present affinity for the carbon of its structure forming carbides that contaminate the tool that looses its properties and wears. Favourable metals are: aluminium alloys, brass, bronze, copper, gold, silver, zinc, beryllium, plumb, tin, indium, plutonium, magnesium (not able for steel, nickel, titanium, molybdenum, cobalt, chrome, vanadium, rhodium and tungsten).
For micromachining the process is suitable to produce small diameter shafts (Ø0.2~Ø0.02 mm) and small slots (using small tailor-made tools). Part cutting becomes an important issue. Mirror finishing is right now its main market, some applications are: laser driving optics, wavelength filtering surfaces, moulds for components of optical quality, etc.
In [A_1], referring to Masuzawa [A_2], in micro metal cutting, the first requirement for micro machining, small unit removal, is satisfied when a high stress that causes shearing of material is applied to a very small area or volume of the workpiece. This means that a highly concentrated force must be applied to an appropriate position of the workpiece. Therefore, assuming that the desired unit removal is around 100 nm, a tool that has its edge sharpened to a radius smaller than 1μm is necessary. The tool material for these processes must be stronger than the workpiece material, and for the case of very small unit removal diamond and hard ceramics are suitable as tool or abrasive material for all processes of this type when the metals are machined. This is gives reason for the application of monocrystalline diamond tools in diamond cutting processes.
[A_1] Metal cutting in microstructures, E. Brinksmeier, O. Riemer, Multi-material Micro Manufacture, W. Menz & S. Dimov, 2005, pp. 19 - 25.
[A_2] Masuzawa, T., 2000, State of the art of micromachining, Annals of the CIRP, 49/2:473-488.