Evaluation and compensation of tool approach mark in end milling operation

In end milling operations, undesired tool approach marks may occur due to the tool deflection by transient cutting force change in the tool approach motion. The tool approach marks have a particularly big influence on the machined surface quality in case of the smooth and continuous surfaces are highly required. Therefore, in this study, a method to reduce the tool approaching mark due to the tool deflection by cutting force in ball end-milling operation is proposed. The influence of the tool deflection onto the machined surface is investigated. Characteristics of the tool approach mark are investigated based on the measured machined surfaces profile. As a result, it is confirmed that the behavior of the tool approach mark can be evaluated by using the proposed machining test. It is also confirmed from the results that the tool approach mark is generated by the difference of tool deflection by changing the actual radial depth of cut during the tool approach motion, A method to reduce the tool approach marks by the tool motion paths with the offset between the retract and approach paths is adopted, and the equation of the offset for effective compensation is proposed. It is experimentally confirmed that the proposed method can effectively eliminate the tool approach marks on the finished surface.