Ultraprecision grinding of microdimple array mold made of cemented carbide using nano-polycrystalline diamond tool

Abstract

A research project was conducted to develop a grinding tool made of nano-polycrystalline diamond adaptable to fabricating a microdimple array (MDA) mold composed of a huge number of microdimples with a diameter of 30 μm, zero flattening, and a surface roughness of less than 10 nmRz on a surface of cemented carbide with a hardness of 2620 Hv. Eight spiral grooves twisted clockwise and counterclockwise and 7 μm in width and depth were formed on a hemispherical working surface with a radius of 0.1 mm to increase the ratio of actual depth of cut (ADC) that represents a specific grinding force. A set of a grinding test, the fabrication of MDA composed of 2107 microdimples and the measurement of the ADC by forming 18 microdimples before and after the MDA fabrication, was performed twice to evaluate the wear resistance of the grinding tool. The grinding test using the grinding tool with grooves twisted counterclockwise revealed that the tool enabled us to increase the ADC by 1.5-fold, compared with the tool without grooves, and that 4214 micrpdimples with a diameter flattening of less than 0.01 and a surface roughness of less than 10 nmRz were successively fabricated. Although it was difficult to fabricate these 4214 microdimples without any diameter change, the standard variation of the microdimple diameter was 0.07 μm when the ADC of the grinding tool became stable with the fabrication of more than 3000 microdimples.

Keywords

• ultraprecision grinding
• microdimple array
• glass lens mold
• cemented carbide
• nano-polycrystalline diamond