Edge profile measurement of micro-cutting tools on a diamond turning machine

Single crystal diamond micro-cutting tools, which are used for fabrication of precision micro-parts, have very sharp tool edges with radii in the range of tens of nanometers or even nanometers. Although there are many types of tools, the tools with a rounded nose are treated in this paper. They can be used for fabrication of very smooth and accurate surface with 3D micro structures such as micro-lens arrays, diffractive optical elements and so on. The machined quality is highly depending on the tool edges' states and it is desired to manage them. This paper presents a measuring instrument based on atomic force microscope (AFM), which is designed and constructed for on-machine measurement of the cutting edge profile. It is a combination of an AFM probe unit for 3D edge profile measurement and an alignment system with an optical sensor for aligning the probe-tip with the tool's edge top so that the measurement can be carried out in a short time. Measurement experiments of micro-tools with (nominal) nose radii of 8 μm and 0.2 mm are summarized to show the performance of the instrument. And the nose radii were evaluated as 7.2 μm and 0.188 mm, respectively.