Analysis and Automation of Polishing Motion of a Skilled Machinist by Handwork for Mold and Die

在模具制造中，数控机床已经实现了模具的自动化加工，但模具型腔表面仍由熟练的机械师手工抛光。本文的目的是研究熟练的机械师手工抛光的机理和性能，并在分析抛光运动和专家知识积累的基础上开发一种自动化抛光工具。得到的结果总结如下：(1)表面粗糙度R随抛光次数N的增加呈指数递减，可定量计算为：R = (R_0-Re)exp(-aN) + Re，其中R_0为抛光前表面粗糙度，Re为最终表面粗糙度，a为指数常数因子。(2)去除率与抛光次数的曲线用两条直线近似表示，两条直线的交点对应于表面能基本完成的临界抛光次数。(3)所开发的自动抛光工具安装在数控机床主轴上，使其可以像熟练的机械师一样手工完成表面加工。(4)采用由砂轮转数(N)、进给速度(f)和抛光次数(N)三个因素组成的新型抛光参数N/(f/ N)，可以在不考虑抛光条件的情况下定量处理表面粗糙度和去渣量。

The automated form machining has already been carried out by NC machine tool in manufacturing mold and die, however, the mold cavity surfaces are still polished by a skilled machinist's handwork. The purpose of this paper is to not only study polishing mechanism and properties of a skilled machinist by handwork, but also develop an automated polishing tool based on the analysis of polishing motion and the knowledge acquisition of experts.The results obtained are summarized as follows: (1) The surface roughness(R) is exponentially decreased with the increase of the number of polishing operation(N) and can be obtained quantitatively according to the following equation: R = (R_0-Re)exp(-aN) + Re where R_0 is surface roughness before polishing, Re is final surface roughness and a is exponential constant factor. (2) The curve of the stock removal vs the polishing times is expressed approximately with two lines and the intersection of the two lines corresponds to the critical polishing times in which the surface can be almost finished. (3) The developed automated polishing tool which is attached to the spindle of NC machine tool makes it possible to finish the surface like a skilled machinist by handwork. (4) Using new polishing parameter(N/(f/n)) consisting of the three factors of wheel revolution(n), feed rate(f) and polishing times(N), the surface roughness and the stock removal can be dealt with quantitatively regardless of polishing conditions.