Study on chip removal mechanism of PCD hall-end milling (1st report) cutting simulation by orthogonal cutting

A polycrystalline diamond (PCD) ball-end mill is effective for processing molds made of hard and brittle materials, such as cemented carbide and ceramics and having fine and complex shapes with a high aspect ratio. The PCD ball-end mill has a distinctive feature of its cutting edge, which it has a simple spherical shape without sharp cutting edge found on conventional cemented carbide and cubic boron nitride (cBN) ball-end mills. The rake angle varies depending on the depth of cut. In cutting using the PCD ball-end mills, flow type chips are observed and mirror finish surface without micro fracture can be realized by adopting the ductile-cutting mode. However, the mechanism of chip generation in this cutting with the PCD ball-end mills has not been fully clarified. In this study, to simulate the cutting mechanism of the PCD ball-end mill, an orthogonal cutting experiment was conducted using an ultrafine PCD cutting insert having nose radius similar to that of the PCD ball-end mill, for basically understanding the chip formation mechanism of the PCD ball-end mill. Consequently, we designed an experimental setup with a spring constant force for applying simulation of thrust force of the PCD ball-end mill. As a result, the chips could be generated at down to -75 degrees of rake angles and the relationship between the negative rake angles and the chip generation mechanisms were clarified.