A Study on Cutting Force in the Milling Process of Glass

The paper discusses the milling process for machining glass without brittle fracture. Although glass is a brittle material, it can be deformed in a ductile mode if the undeformed chip thickness is less than a micrometer. The undeformed chip thickness starts at zero in the up-cut milling process. Glass, therefore, can be machined without brittle fracture at the beginning of the cut, and then brittle fracture occurs at a certain undeformed chip thickness. The area of brittle fracture can be finally removed with the cutter feed. As a result, the machined surface can be made in a ductile mode of the cutting process. The cutting process in the up-cut milling of glass is discussed and the cutting force measured. The cutting force gradually increases with the cutter rotation at the beginning of the cut, and oscillates about a constant mean value after a certain undeformed chip thickness. The transition from ductile to brittle mode is specified in the change of cutting force. The effect of cutting conditions on the transition is investigated with the mechanism of the milling process. It is proved that the machined surface without brittle cracks can be obtained in a large radial depth of cut at a high feed rate.