Relation between Drilling Conditions and Tool Life in Micro Drilling (2nd Report)

—Researches on Applying Ultrasonic Vibration on Machining Fluid—

Abstract

The most important problem in the micro drilling of ductile materials such as steels is a tool breakage due to poor tool rigidity and chip removal. The cavitation, which is generated by ultrasonic vibration applied on machining fluid, accelerates the chip removal. This paper deals with thrust force, tool life, chip geometry etc. for various drilling conditions in drilling SUS304 with (Ti, Al) N coated tool with a diameter of 0.1mm. In addition, the effects of pre-drilling using a center drill on tool life and of G73 cord on the machining efficiency are investigated. The obtained results are as follows. The thrust force hardly varies with feed speed and increases with step feed. The micro drilling assisted with cavitation achieves very longer tool life compared to the conventional drilling. Furthermore, the quick bite leads to longer tool life. The smaller feed speed and the larger step feed, respectively, bring out the shorter tool life.