基于VRML的模具边界提取方法与加工轨迹优化研究

VRML-based mould boundary data extraction and processing trajectory optimization

为解决气压砂轮进动抛光在模具边界区域的振动加剧、边界棱线过度磨损和气压砂轮失效等问题,将VRML技术应用到气压砂轮进动抛光轨迹规划中。经过对VRML文本内容的分析,采用一系列三角形平面取代原始的多边形平面和自由曲面的VRML描述模型表面的方法,建立了文本数据与模型边界线之间的对应关系,提出了一种基于VRML的模具边界线三维解析式提取方法,并将该方法应用到气压砂轮进动抛光轨迹优化中;通过限制气压砂轮切削速度方向与模具边界外法向量的夹角,获得了理想的切削速度分布特性。实验及研究结果表明:通过该优化方法获得的模具边界线数据具有较好的完整性和准确性,适用于各种复杂形貌的模具零件的轨迹优化,并可通过调整阈值来满足具有不同曲率曲面的识别要求。

In order to solve the problems of increasing vibration,excessive removal of material and pneumatic wheel failure in polishing the 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 free surface 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 boundary lines based on VRML technology.It was evaluated in the pneumatic wheel precession polishing trajectory planning process.By restricting the angle between cutting speed direction vectors and the boundary normal vectors near the boundary lines,an ideal distribution of cutting speed 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.