Research on the ploughing force in micro milling of soft brittle crystals
Abstract The ploughing force can be assigned to supervisory control of the tool wearing and machining process on line in micro milling, for the reason that the ploughing force is closely related with the processed surface quality and radius of cutting edge. A new theoretical model is established to determine the ploughing force in micro milling of crystals with soft brittle characters in consideration of the cutting edge roundness, and it is verified by Finite Element Method. The ploughing force decreases quickly with an decrease of the cutting edge roundness, and it can be controlled to be less than the shearing force, which helps for obtaining a good machined surface quality, under the condition that the radius of cutting edge is less than 2.8 mm or the feed speed is larger than 5 mm/z when the radius of cutting edge is larger than 4.2 mm. Meanwhile, a large feed speed would bring heavy tool traces on the processed surface of soft brittle crystals, destroying the processed quality. The energy consumption is researched by investigating the specific cutting force, showing that the energy consumption has a sharp increase with a small feed speed. The energy consumption is mainly caused by the ploughing effect, especially for tools with blunt cutting edge. Therefore, both the micro mill with sharp tool edge or blunt tool edge (under the cutting condition that the feed speed almost have equal value to the radius of cutting edge) are highly recommended for micro end milling of soft brittle crystals.
International Journal of Mechanical Sciences