Abstract

A methodology for reliable measurement of the surface roughness of solid freeform (SFF) parts is desired. Currently the ASME B46.1 Surface Texture Testing Standard specifies a method for determining a representative surface roughness Ra value for a single line, but not an area. From multiple single line measurements a representative Ra value can be determined for textured surfaces. It is desirable to optimize the number of line measurements of given length that on average provide a representative Ra value. The surfaces of two indirect-SLS metal slabs were measured using this procedure in three directions and a statistical analysis based on the Student t-test was performed on the data to determine the number of measurements needed to estimate the Ra value within a 10% error given a 95% confidence interval. The minimum number of required line measurements (of length 15000 ?m) ranged from 4 to 9 for three arbitrary angular measurement directions: 0°, 45° and 90°. Moreover, the Ra variation with line measurement direction corresponded to approximately 10%.