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Alternative TitleHigh Precision and High performance Tool Path Planning and Interpolation Methods for Complex Surface
Thesis Advisor刘伟军 ; 赵吉宾
Keyword轨迹规划 轨迹连接 高速加工 双螺旋轨迹 Nurbs拟合
Call NumberTG659/Z73/2015
Degree Discipline机械电子工程
Degree Name博士
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract本文将围绕型腔数控加工轨迹规划中的一些深层次问题展开论述,着重解决其中的光顺加工的关键技术问题,以期对模具数控加工提供技术支持。本文的主要研究内容和贡献如下:1. 针对现有的五轴加工轨迹生成方法在处理加工过程中的曲面形状突变及干涉情况时,会在前后加工点处产生刀轴矢量的剧烈变化,这将不可避免地造成刀具的破损并直接影响加工质量,解决这一问题的常用方法是生成刀轴光顺轨迹。针对光顺刀轴矢量的生成问题,首先在非干涉域内有效插入限定的加工点位,保证刀轴矢量的整体优化;同时在干涉域内采用改进的C-Space法,生成刀轴矢量光顺可行域。实例表明,将该方法应用在复杂型面的加工中可以有效地生成光顺刀轴矢量、高效处理加工过程中全局及局部干涉情况,避免过切加工的同时不增加加工点的数目,实现了刀轴矢量的优化。2.详细地论述了一种通过偏微分方程生成等值线进而生成光顺性非常高的螺旋轨迹的规划方法。该方法由偏微分方程的热传导模型,计算得到映射参数域内满足加工参数的温度等值线,制定映射规则并在标准参数域内规划出加工轨迹,从而在对应参数域内映射生成螺旋轨迹,并将该轨迹映射到参数曲面上获得曲面的螺旋加工轨迹,该轨迹可以实现无退刀加工。采用上述算法进行了仿真,仿真结果表明该方法优于现有加工方法,可实现基于参数曲面及裁剪曲面的复杂型腔的高速加工。3.本文对上述螺旋轨迹规划问题进行了进一步研究,详细论述了参数化双螺旋轨迹生成方法及根据曲面几何特征进行合理分割的方法。并针对传统3D轨迹连接方法的不足,提出了一种简单有效的双螺旋轨迹连接方法。该方法根据待加工区域的几何特征,在提高凸度或圆度的前提下尽量进行岛屿环的分割轨迹,对剩余区域进行岛屿链的分割,并针对狭长的瓶颈型区域进行拆分,保证生成的轨迹尽量均匀,可有效提高轨迹的光顺性。该方法可实现大型复杂型腔或带有岛屿型型腔的分区域加工。4.本文针对通过刀具半径补偿方法由工件边界偏置获得的初始路径,拟合出适用于光顺、高速及高精加工的NURBS形式的刀具路径的问题进行了研究。根据长度及连续短块的准则,这些偏置线性段可以被认为是连续微段或长直段。转接处位于曲率值超过设定的曲率阈值处或曲率变化剧烈处,或任何的长直段两端。在加工过程中,该NURBS拟合模块可以预读若干连续微段并将其实时转换为参数曲线。在转换过程中,参数曲线及非拟合曲线的过渡处的位置、斜率甚至曲率均可以保证连续,因此具有良好的光顺性。其次,加减速规划模块可以确定拟合曲线及非拟合的长直段间的过渡段的转接速度,以及拟合曲线的转角速度。
Other AbstractThis paper will discuss some deep-seated problems in the pocket tool-path planning and focus on solving some key technical problems to provide the technical support for the mold NC machining with motion smoothness. The main research contents and contributions are as follows: 1. Dealing with existing work in the mutation and obstacles of sculpture surfaces, the tool shaft often required to make drastic changes in its orientation between two neighboring contact points. This will inevitably cause tool damage and a direct impact on the processing quality. The usual solution to this problem is to smooth the tool path in the configuration space. The method which proposed here is a simple and effective tool axis vector optimization method. It will first insert interpolation points in the non-interference region within the effective processing to ensure that the overall optimization of the tool axis vector. In themeantime to improve the C-space method in the interference region, the tool axis vector smoothing the feasible region will be generated. Examples show that this method can effectively generate complex surface machining tool axis vectors, high-activity handling theprocessing of global and local interference situation, avoid overcut and not increase the number of processing points, achieve the optimization of tool axis vectors. 2. This paper proposes a novelty spiral tool path generation algorithm for 5-axis high speed machining. The processes are carried out which are using partial differential equations of heat conduction model and defining the projection parameters of projection region for the calculation of contours within the projection region, selecting out of the temperature contours which meet the processing conditions, defining the mapping rules and planning processing trajectory within the standard parameter domain, then mapping trajectory to the corresponding parameter domain to generate spiral trajectory, and mapping the spiral trajectory to the parametric surface to generate the spiral processing trajectory. This processing trajectory can be achieved without retracting processing.Using the above algorithm to obtain the simulation results, it shows thatthe new method is superior to traditional processing methods. The results also show that this method can achieve high-speed processing based on the complexity of parametric surfaces and cavity of trimmed surface. 3. Moreover, a new double spiral tool-path generation algorithm for HSM is proposed and the tool-paths linking method is planned for complex multi-domains. This method can realize the precision milling of complicated parametric surface without tool retractions, and meanwhile it improves the uniformity of the tool-paths and machining efficiency. Our method has been experimented in several simulations and validated successfully through the actual machining of a complicated pocket. The results indicate that this method is superior to other existing machining methods, and it can realize HSM of complicate-shaped pocket based on parametric surface. 4. This paper focuses on developing an algorithm that can generate toolpaths in NURBS form for smooth, high speed and accurate machining. The initial toolpaths are obtained by tool radius compensation method which is based on the workpiece boundary offsetting. According to different lengths and the continuous short block (CSB) criterion, these offset linear segments can be regarded as CSBs or long straight segments. Junctions are located where the curvature value is greater than the preset curvature threshold value or where it changes abruptly, or at the two end points of any long straight segment. During machining, the NURBS fitting module first looks ahead several CSBs and converts them into parametric curves in real time. During the conversion, continuities of the position, slope or even curvature at the transition of the parametric curves and unfitted line segments can be guaranteed. Then the acceleration/deceleration feedrate-planning scheme is proposed to determine the transition feedrate at the junction between the fitted curves and unfitted long straight segments, and the corner feedrate within the fitted curve.
Contribution Rank1
Document Type学位论文
Recommended Citation
GB/T 7714
周波. 复杂曲面精密高效数控加工轨迹规划及插补方法[D]. 沈阳. 中国科学院沈阳自动化研究所,2015.
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