2015 年 81 巻 1 号 p. 68-73
Various shaped ball end mills having a large helix angle, multiple flutes and their irregular intervals of the cutting edges are produced and widely used. However, relationships among these variably geometrical components of the tool, cutting forces and tool behavior during milling have not yet been systematically explained. This investigation deals with the tool configuration which makes effect on reducing the movement of the tool axis caused by tool deflection and suppressing chatter vibration. In this report, milling process with ball end mills whose circumferential cutting edges arranged at equal intervals is mainly treated, and cutting forces in the case of one to six circumferential cutting edges are estimated by using a cutting model proposed in previous papers. Then, to clarify the effect of the number of circumferential cutting edges on tool behavior, finite element models of ball end mills having three or four cutting edges are constructed by using geometrical data of the cross-section of a standard-type end mill. Furthermore, the data of cutting forces predicted is applied to these models to analyze the deflection of the tool axis. It is shown that the fluctuation in cutting forces and the tool axis trajectories can be considerably reduced in the case of providing four circumferential cutting edges. In addition, cutting forces of two flutes ball end mill having unequal interval of the cutting edges are estimated, and relationship between interval of the cutting edges and fluctuation of cutting forces is discussed.
