Algorithms and machining experiments to reduce depth errors in servo scanning 3D micro EDM
Algorithms and machining experiments to reduce depth errors in servo scanning 3D micro EDM
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DOI：
10.1016/j.precisioneng.2014.02.002
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发表时间：
2014-07
影响因子：
3.6
通讯作者：
H. Tong;Long Zhang;Yong Li
中科院分区：
文献类型：
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作者：
H. Tong;Long Zhang;Yong Li
伺服扫描三维微细电火花加工（SS-3D MEDM）中，为真实的实时补偿电极轴向磨损，保持放电间隙的轮廓扫描过程会使三维微细腔深度误差逐层累积。分析了误差产生的原因，提出了一种层深度约束算法（LDCA）和一种S曲线加速算法（SCAA）来减小深度误差。通过LDCA，可以通过控制每个扫描点处的工具电极进给最大值来避免过切误差。SCAA算法作为LDCA算法的一种补充算法，可以补偿扫描路径起点和终点处的不连续加工误差。并对算法的实现过程和控制策略进行了描述。本研究的目的是高效率地加工具有高形状和表面精度的复杂三维微腔。利用计算机辅助制造软件Pro/Engineer规划复杂的三维扫描路径，并进行了加工实验验证。实验结果表明：采用直径为80 μ m、转速为1000 r/min的工具电极，实现了典型三维微小型腔（<800 μm）的自动加工，显著提高了微小型面和边缘的加工精度，深度误差可控制在2 μm以内，材料去除率达到2.0 × 104μm3/s。在未知边缘或空心工件上设计的三维微腔可以成功成形。
In servo-scanning 3D micro electro discharge machining (SS-3D MEDM), the depth errors of 3D micro cavities are accumulated layer by layer due to the contour scanning process with keeping discharge gap for compensating axial electrode wear in real time. In this research, the errors’ causes were analyzed, and then a layer depth constrained algorithm (LDCA) and an S-curve accelerating algorithm (SCAA) were proposed to reduce the depth errors. By LDCA, over-cutting errors can be avoided by controlling a tool-electrode feed maximum at every scanning spot. As a supplementary algorithm for LDCA, SCAA can compensate insufficient-machining errors at start and end of scanning paths. Implementation process and control strategy of the algorithms were also described. The purpose of this research is to efficiently machine complex 3D micro-cavities with high accuracies of shape and surface. By use of computer-aided manufacturing software of Pro/Engineer to plan complex 3D scanning paths, machining experiments were carried out to verify the proposed algorithms. The experimental results show: Typical 3D micro cavities <800 μm can be automatically machined, and the machining accuracies of micro surfaces and edges are obviously improved, and the depth errors can be controlled within 2 μm, and the material removal rate reaches 2.0 × 104μm3/s with tool electrode of∅80 μm and its rotational speed of 1000 r/min. In addition, the 3D micro cavities designed on unknown edge or hollow workpieces can be successfully formed.