摘要
几何造型和刀具运动轨迹的生成是实施数控加工的两大关键技术,其中几何造型是数控刀具轨迹的基础,而零件数控加工的准确性则只能在合理的刀具轨迹的前提下才能予以保证。刀具轨迹规划的合理与否,不仅直接关系到切削效率、加工精度、加工干涉,而且还影响机床的动力性能及刀具的使用寿命。
目前,在生产实际中刀具轨迹的路径规划完全通过人机交互的方式手工完成,过分依赖工程师的经验;各种工艺参数以及工程数据也只能凭借工程师的经验和手册,未能实现自动化。
本文主要根据生产实际中的需要,针对自由曲面进行刀具轨迹的路径规划,并以沈阳华晨金杯汽车公司的海狮面包车某覆盖件为样件进行研究。
应用反求工程的原理,利用我院实验室LK G90CS15.10.8三坐标测量机,对自由曲面的实物样件进行表面数据的采集,得到大量、散乱的点云数据。通过Imageware软件对点云进行处理,去掉噪声点,采用基于四边域参数曲面的重构技术,构造出自由曲面。
对自由曲面的走刀模式进行了较深入的研究,其中包括行切走刀模式、环切走刀模式、螺旋走刀模式,重点研究了行切走刀模式。根据换行时的加减速、加工时匀速的特点,以加工效率为目标,建立了刀具时间数学模型。采用C++Builder软件编制数学模型的程序,读取商用CAD/CAM软件的刀位源文件,计算刀具轨迹加工时间,实现了走刀方向的自动优化。
针对粗加工建立刀具轨迹规划系统,赋予计算机知识的推理能力,把自由曲面规则化,根据形状特征和工艺特征自动优化刀具轨迹。
刀具轨迹规划系统的建立,将弥补商用CAD/CAM软件依赖人的经验的缺点,为我国CAD/CAM软件的国产化奠定基础。
Geometry model and generation of cutter path are two key technologies for NC machining. In the two technologies, geometry model is the base for calculating cutter path and the accuracy of NC machining only depends on the rational cutter path. The appropriate planning of cutter path not only direct influence stock-removing efficiency, machining precision and machining interference but also influence the dynamic performance of machine tool and operating life of cutter.At present, tool-path programming is accomplished by manual man-machine alternation completely and excessively depends on the experience of engineers. The diversified processing parameters and the engineering data also depend on handbooks and experience of engineers, and the automatization can not be achieved.Based on the need of actual production, the paper studies a master piece which comes from Haise microbus made in Shenyang Brilliance Jinbei automobile limited corporation aiming at the tool-path programming of free surface.Based on the theory of reverse engineering and three-CMM, the paper gathers many data from the free surface of the sample part and gains points cloud. With Imageware software, the noise points is eliminated. Then, free surface is formed by reconstruction technique.The dissertation studies the feed pattern of free surface deeply, including linear feed pattern, circular feed pattern and gyroidal feed pattern, and the linear feed pattern is emphasis. Aiming at high machining efficiency, the mathematical model of time is founded on the base of accelerate or decelerate of changing line and smooth speed in the course of machining. Using C++ Builder software, the program of mathematical model, is worked out. It can read the source file of cutter position from commercial CAD/CAM software and calculates machining time of tool-path. Ultimately, the auto-optimization of cutting orientation is achieved.
Aiming at rough machining, the paper founds tool-path programming system and makes computer have the capability of intellective discursion, makes free surface to be regular and auto-optimizes tool-path according to the character of shape and technics.Tool-path programming system will make up the disadvantage that the commercial CAD/CAM software excessively depends upon engineer. This founds the base of making CAD/CAM software homemade.
引文
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