| Abstrakt: |
Stylus profilometry is one of the most significant technologies to measure freeform surfaces. However, the lateral force on a stylus usually leads to invalid measurements, especially for surfaces with a large curvature, due to the structure of the cantilever. Thus, we propose a novel radial scanform measurement for such surfaces, with an aim to reduce measurement errors. The precise 3D form of the workpiece was obtained using a series of profiles measured individually along the radial direction via a rotary mechanism. The lateral slope and force on the stylus for every profile are therefore much lower than those measured by traditional raster scan form measurements. We also propose a stable and accurate two-step registration procedure to evaluate the freeform surface form error; this eliminates the need to calibrate the spindle of both the workpiece and the rotary mechanism. A freeform surface with a 30 mm diameter aperture and 24 mm curvature radius was measured on a Form Taylorsurf PGI 1250A profilometer. Compared to traditional raster scan 3D form measurements, the peak-to-valley and root mean squared values of the form error decrease from 409.415 µm and 67.490 µm to 4.967 µm and 0.658 µm, respectively, via the proposed method. Results show that our method solves the problems of measuring surfaces with a large curvature. [ABSTRACT FROM AUTHOR] |
