Laboratory for Manufacturing and Sustainability

Back cutting is a special condition that occurs when there is tool run-out, uneven tool wear on the inserts or machining over the same region in opposite directions in two different passes. As the tool progresses along a tool path the instabilities mentioned might cause the back half of the cutter to machine the workpiece. This condition is commonly referred to as back cutting. The most common way of observing the presence of back cutting is the reversal in the direction of tool marks. A series of experiments were performed to gauge the actual effect on process performance due to back cutting. The results surprisingly showed that back cutting does not have a serious impact on the burr formation. Pictures of burrs under an optical microscope shows that back cutting do not create burrs but merely machines over the burrs created from forward cutting. Experiments performed with different back cutting depths produced identical results.

The study also revealed that the tool wear which causes nose rounding is the more significant cause of burrs not explained by prediction theories. Two different strategies, tool geometry based and tool path based are proposed to avoid kinematic conditions that promote burr formation with worn tools. The results from these strategies are presented at the end of this paper.