基于STL模型的数控加工仿真关键技术研究

发布时间：2018-03-01 13:23

本文关键词： 数控加工仿真刀具扫描体 STL模型布尔运算效率优化空间分解精度验证　出处：《浙江大学》2016年博士论文　论文类型：学位论文

【摘要】：精度和速度的权衡是数控加工仿真不可回避的矛盾问题。基于STL模型的数控加工仿真方法具有仿真精度高且模型数据便于交换的优点,但是由于STL模型之间的布尔运算计算复杂且计算量大,因此也存在着仿真速度慢的不足。为了在保证仿真精度的前提下提高仿真速度,本文提出并实现了基于STL模型的数控加工仿真方法,重点研究了仿真效率的优化方法。本文研究内容如下:刀具扫描体是数控加工仿真的前提,对切削过程的动态仿真起着重要的作用。本文以包络理论为基础,根据刀具的几何特点和运动特点,提出了一种结合插值法、离散法和二分查找法计算包络点位置的方法,实现了对刀具扫描体的快速准确建模。同时,对刀具扫描体建模过程中可能出现的自相交问题,提出了预判与解决的方法。本文提出的刀具扫描体建模方法适用于任意形状的回转刀具,并且适用于多轴数控加工仿真。STL模型的布尔运算是数控加工仿真的关键算法,切削过程的动态仿真就是通过工件和刀具扫描体这两个STL模型之间的连续布尔求差运算实现的。为保证数控加工仿真的精度,本文实现了一种STL模型的精确布尔运算算法,研究了算法中出现的三角面片共面、共边和无效交线等几何奇异性问题,提高了算法的可靠性。该算法由三角面片的相交性测试、相交三角形的区域剖分、相对位置关系测试等步骤组成。在基于STL模型的数控加工仿真中,影响仿真速度的关键因素是布尔运算中的相交性测试。为了对相交性测试进行优化,本文综合实体分割法和空间网格法的优点将两者结合使用。首先使用实体分割法将一个完整的工件分割为若干个子工件,通过包围盒算法快速排除不可能与刀具扫描体相交的子工件。对于可能与刀具扫描体相交的子工件,采用空间网格法将相交三角面片的搜索范围缩小到空间单元格内部,从而减少了相交性测试的计算量并提高了数控加工仿真的效率。最后以注塑模具型芯件的加工仿真为例对这两种方法的优化效果做了测试,结果表明STL模型越复杂优化效果越显著。在研究刀具扫描体快速造型算法、STL模型布尔运算算法以及相交性测试优化算法的基础上,实现了动态切削仿真并对仿真结果进行了几何精度验证。几何精度验证算法主要由采样点计算和有向距离计算两个步骤组成。通过几何精度验证算法可以将仿真结果与设计模型进行定量分析比较,从而检验数控编程是否满足精度要求。
[Abstract]:The tradeoff between precision and speed is an unavoidable contradiction in NC machining simulation. The NC machining simulation method based on STL model has the advantages of high simulation precision and easy exchange of model data. However, due to the complexity and complexity of the Boolean operations between STL models, there is also a lack of slow simulation speed. In this paper, the simulation method of NC machining based on STL model is put forward and realized, and the optimization method of simulation efficiency is studied emphatically. The contents of this paper are as follows: tool scanning is the premise of NC machining simulation. In this paper, based on envelope theory and according to the geometric and kinematic characteristics of cutting tools, a new method for calculating the position of envelope points is proposed, which combines interpolation method, discrete method and binary search method. At the same time, the self-intersection problem that may occur in the modeling process of tool scanning volume is realized. The method of tool scanning volume modeling proposed in this paper is suitable for any shape rotary tool, and the Boolean operation of multi-axis NC machining simulation .STL model is the key algorithm of NC machining simulation. The dynamic simulation of cutting process is realized by the continuous Boolean difference operation between the two STL models of workpiece and tool scanning. In order to ensure the accuracy of NC machining simulation, a precise Boolean algorithm of STL model is implemented in this paper. In this paper, the geometric singularity problems such as triangulated plane coplanar, common edge and invalid intersection are studied, and the reliability of the algorithm is improved. The algorithm is tested by the intersection of triangles, and the region of intersected triangles is divided. In the NC machining simulation based on STL model, the key factor affecting the simulation speed is the intersection test in Boolean operation. This paper combines the advantages of entity segmentation method and spatial grid method to combine the two methods. Firstly, a complete job is divided into several sub-jobs by using entity segmentation method. The bounding box algorithm is used to quickly eliminate the sub-workpieces that cannot intersect with the cutter scanning body. For the sub-workpieces that may intersect with the tool scanning volume, the search range of the intersected triangular slices is reduced to the inner of the spatial cells by the spatial grid method. Therefore, the calculation of intersecting test is reduced and the efficiency of NC machining simulation is improved. Finally, the optimization effect of these two methods is tested by taking the machining simulation of injection mould core parts as an example. The results show that the more complex the STL model is, the more significant the optimization effect is. The geometric precision verification algorithm is mainly composed of sampling point calculation and directed distance calculation. The geometric precision verification algorithm can be used to verify the geometric accuracy of the simulation. The results were compared quantitatively with the design model. In order to verify whether NC programming meets the accuracy requirements.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG659

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