Abstract
This paper deals with an experimental investigation of high-speed face milling of polybenzimidazole (P.B.I.) using a fine crystalline diamond coated tool which has reshaped sharp edge. Especially, the effects of a sharpened cutting edge and an increasing cutting speed on machined surface are investigated. It has been confirmed that the edge of a diamond coated tool could be reshaped in a sharpened form by a heat chemical polishing. The diamond coated tool which has a reshaped edge is superior to a normal coated diamond tool in machined surface with little damage by cracks. Moreover, this tool when it has a rake angle of 10 degree is effective in controlling cracks. Furthermore, as a result of the investigating the effects of different speeds on damages to a machined surface, it is clear that the best machined surface with very little damage is obtained at a cutting speed of 40.0 m/s. At less than 40.0m/s, the damage was determined by mainly micro-crack and, on the other hand, tear damage to the machined surface was observed at speeds beyond 40.0m/s. The viscoelastic behavior of P.B.I. material accompanying change of cutting temperature had influenced these kinds of damages, and it showed clearly for the temperature of 650K which begins to produce the viscosity to be equivalent to cutting speed 40 m/s. Also, a drop in the bending strength after cutting can be limited to 2%.
