非线性误差对数控极坐标凸轮磨削过程的影响

Influence of Non-linear Error Upon the Process of Cam Nc Polar Grinding

分析了数控极坐标凸轮磨削过程中磨削点瞬时进给速度,瞬时接触状态和金属去除率(磨削负荷)等的变化规律。指出,实行简单线性插补时会出现非线性误差,它对磨削过程有重要的影响:①使插补轨迹脱离理想轨迹,产生在程序段范围内的波纹起伏;②使插补包络脱离理想包络,出现增厚或过切的波纹度,影响形状和尺寸精度;③改变砂轮与工件的瞬时接触状态,出现瞬时飘空、瞬时面接触;④使磨削点的转移出现跳跃、回扫等现象,瞬时进给速度不再能反映瞬时金属去除率,两者都出现异常的变化。以上各点,都会破坏磨削过程的平稳性。

The behaviors of grinding point's instantaneous feedrate, contact status and metal removal rate (grinding load) during cam NC polar grinding process are deeply analyzed. It is pointed out that under simple linear interpolation, there will be non-linear error, which has important influences upon the grinding process: ① It makes the interpolated locus deviate from the ideal locus and leads to fluctuation. ② It makes the interpolated envelope deviate from the ideal envelope and leads to under-cut and/or over-cut waviness and decreases the formal and dimensional accuracy. ③ It changes the instantaneous contact status between grinding wheel and cam and leads to instantaneous surface contact/non-contact. ④ It makes the grinding point transfer along the machined surface jumping/back scanning, and the instantaneous feedrate can't reflect the instantaneous metal removal rate any longer. All of above certainly destabilize the grinding process.