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自动化的成形加工，但模具型腔表面的抛光仍然需要熟练的机械师手工进行。本文通过对抛光运动的分析和专家知识的获取，不仅研究了手工抛光的机理和性能，而且开发了一种自动抛光工具。研究结果表明：(1)表面粗糙度(R)随抛光次数(N)的增加呈指数下降，并可根据以下方程定量计算：R=(R0-Re)exp(-An)+Re，其中R0为抛光前的表面粗糙度，Re为最终表面粗糙度，a为指数常数。(2)磨料去除与抛光时间的关系曲线近似用两条直线表示，两条直线的交点对应于表面几乎能被抛光的临界抛光时间。(3)研制的自动抛光工具安装在数控机床的主轴上，可以像熟练的机械工人一样手工加工表面。(4)采用由砂轮转速(N)、进给速度(F)和抛光次数(N)三个因素组成的新的抛光参数(N/(f/n))，无论抛光条件如何，都可以定量地处理表面粗糙度和磨削量。

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.