Prevention of Chatter Vibration in Ball End-Milling Operation of Curved Surfaces with Cutting Edge of Reduced Tool-Chip Contact Length

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The etrects of ball end-mill with cutting edge of reduced tool-chip contact length upon prevention of chatter vibration are examined experimentally in die sinking operation. The operation is performed in the manner of x - z axs control with y axis pick feed for a die cross-section having circular parts, slant parts and flat bottom. It is verified that the reduced contact edge is always effective, regardless of cutting conditions used, radius of the circular part, inclination of the slant, and up or down pass of the end-mill. The threshold depth of cut for chatter occurrence is made 1.5-3 times as much as conventional cutting edge.An analytical system is developed, which enables us to predict three components of cutting force (without chatter) during the end-milling of any cutting conditions by only using orthogonal cutting data as data-base. The predicted force components are proved to be in good agreement with experimental results.This system is further developed to be adapted for dynamic cutting process with chatter vibration, and computer simulation of chatter occurrence is made possible. Through the simulation, it is revealed that the reduced contact length suppresses the cutting force variation when some disturbance is introduced in undeformed chip thickness, hence it would reduce excitation of the vibration system. The simulation system, however, has some deficiencies at present and is not able to predict the stability threshold which agrees with experimental results. The improving trials are still going on.