Experimental Study of the Wear of Diamond Coated Micro End Mills

Abstract

The demand for the miniaturization of complex components has led to the growth of manufacturing methods capable of producing truly three dimensional parts using traditional en-gineering materials with favorable mechanical properties. Mechanical micromachining techniques have emerged for the production of these components as other methods are not capable of producing many of the desired component prop-erties. Micro end milling is one such mechanical microm-achining technique. It is able to produce three-dimensional features with high aspect ratios from various materials, such as aluminum, copper, steel, and titanium. Currently, the standard material used for micro end mill tooling is sin-tered tungsten carbide with a cobalt binder. However, its brittle nature coupled with the micro-scale cutting fea-tures of the end mills often result in rapid tool degradation. Soft, ductile materials tend to adhere to the tool cutting surface, easily clogging the micro-sized flutes. This results in high cutting forces and force spikes, drastically reducing the tool life. On the other hand, hard materials tend to increase the abrasive wear rate on the tool cutting edges or cause catastrophic edge failures. Micro end mills typi-cally experience much higher wear rates when compared to macro-sized end mills due to the relative size of the chip load compared to the cutting edge radius of the tool and the overall size of the tool. Due to this fundamental dif-ference during the cutting process, many of the wear charac-teristics and tool life knowledge for conventional tooling may not apply to micro end milling. Even many of the standards developed to determine tool life and tool wear cannot be applied for micro end mill testing because they are based on the typical cutting parameters and chip loads for macro scaled milling operations. As such, micro end milling production has been severely limited because of the amount of "guess work" surrounding tool life. This study will investigate tool life and wear of nanocrystalline dia-mond (NCD) coated and uncoated tungsten carbide (WC) micro end mills during milling of 6061-T6 aluminum.