Analysis on Specific Cutting Resistance Variation by Tool Angles Based on a Concept of Representative Stres

ABSTRACT In the past, prism patternshave been linear triangular shapeswith a 90° angle; however, new micro prism patterns having acute angles or obtuse angles have recently been the subject of demandin the display, lighting and photovoltaic industries. Micro-cutting experiments for micro-prism patterns having 60°, 90°, and 120° angles on an electroplated Ni mold were performed and it was found in this studythat the specific cutting resistance increased with a decrease in the tool angles (prism pattern angles). The cause of this variation had been thought to be the increase of the ploughing force due totip rounding and the friction force due to the edge effect. However, the depth of the cut was large enough that it was possible to neglect these effects. Therefore, this study introduced the concept of representative stress of indentation. The measured stress was varied according to the indentation depth eventhoughthetestedspecimenswereidentical ; the varied stress was termed the representative stress. According to indentation theory, the strain that the Ni mold experienced increased with a decrease in the tool angle. Based on the stress-strain relationship, higher strain means higher stressand higher specific cutting resistance. Therefore, the specific cutting resistance was higher at smaller tool anglesthat had higher strain and stress.