CHARACTERIZING FORM, WAVINESS, AND ROUGHNESS OF MICRO EDM ELECTRODES

摘要

Micro tools produced by μEDM processes such as WEDG have small diameters and long lengths. In prior work, these tools were characterized by either diameter measurements or scanning probe microscopy over small surface areas on the tools. In this paper, we describe a new metrology technique useful in characterizing the entire length of these high aspect ratio tools using scanning white light interferometry and 2D profiles. These profiles indicate variation in the surface height with sub-nanometer resolution along the entire length of the tool, which may be a few millimeters in length. The profiles are separated into form, waviness, and roughness profiles using frequency domain filtering. Based on spectral analysis, wavelengths of 10 μm and 100 μm were found to reasonably separate roughness from waviness and waviness from form. The computation of height parameters, like R_a and R_q, and shape parameters, like R_(sk) and R_(ku), are quantitative metrics useful in comparing the precision of micro tools.