VRML-based mould boundary data extraction andprocessing trajectory optimization
JI Shi-ming，ZHANG He-teng，JIN Ming-sheng，ZHANG Li
（Key Laboratory of E&M，Ministry of Education & Zhejiang Province，Zhejiang University of Technology，Hangzhou 310014，China）
Abstract：In order to solve the problems of increasing vibration，excessive removal of material and pneumatic wheel failure in polishingthe neighborhood of mould boundaries by pneumatic wheel precession polishing technology，the virtual reality modeling language（VRML）technology was applied to the trajectory planning. After the analysis of VRML text content，it's clear that the polygon plane and freesurface of the original model were replaced by series of triangular planes，and the corresponding relationship between the text data and
the model's boundary lines was established. A method was presented to extract the three-dimensional analytical expression of boundarylines based on VRML technology. It was evaluated in the pneumatic wheel precession polishing trajectory planning process. By restrictingthe angle between cutting speed direction vectors and the boundary normal vectors near the boundary lines，an ideal distribution of cuttingspeed was obtained. The results show that this method is capable to obtain precisely a full set of boundary lines of any models with
complex topography，and can recognize surfaces with different curvatures by adjusting the threshold.
Key words：pneumatic wheel；precession polishing；boundary extraction；virtual reality modeling language（VRML）