數(shù)控機床相關(guān)畢業(yè)設(shè)計翻譯---通過熱量誤差補償來改善數(shù)控機床的精確度-數(shù)控設(shè)計-文庫吧
2025-04-17 01:21 本頁面
【正文】 on of the expansion of spindle , the distortion of the spindle housing , the expansion of three axes and the distortion of the column. Due to the dimensional elongation of leadscrew and bending of the column , the thermal errors are not only timevariant in the time span but also spatialvariant over the entire machine working space. In order to measure the thermal errors quickly , a simple protable gauge , i. e. , 1D ball array , is utilized. 1D ball array is a rigid bar with a series of balls fixed on it with equal space. The balls have the same diameter and small sphericity errors. The ball array is used as a reference for thermal error measurement . A lot of preexperiment s show that the thermal errors in zaxis are far larger than those in xaxis and yaxis , therefore major attention is drawn on the thermal errors in zaxis. Thermal errors in the other two axes can be obtained in the same way. The measuring process is shown in . A probe is mounted on the spindle housing and 1D ball array is mounted on the working table. Initially , the coordinates of the balls are measured under cold condition. Then the spindle is run at a testing condition over a period of time to change the machine thermal status. The coordinates of the balls are measured periodically. The thermal drift s of the tool are obtained by subt racting the ball coordinates under the new thermal status f rom the reference coordinates under initial condition. Because it takes only about 1 min to finish one measurement , the thermal drifts of the machine under different z coordinates can be evaluated quickly and easily. According to the rate of change , the thermal errors and the rotation speed are sampled by every 10 min. Since only the drift s of coordinates deviated from the cold condition but not the absolute dimensions of the gauge are concerned , accuracy and precise inst rument such as a laser interferometer is not required. There are only four measurement point s z 1 ,z 2 , z 3 , z 4 to cover the zaxis working range whose coordinates are 50 , 150 , 250 , 350 respectively. Thermal errors at other coordinates can be obtained by an interpolating function. Previous experiment s show that the thermally induced displacement between the spindle housing and the working table is the same with that between the spindle and table. So the thermal errorsΔ z measured reflect those in real cutting condition with negligible error. In order to obtain a thorough impression of the thermal behavior of the machine tool and identify the error model accurately , a measurement strategy is developed. Various loads of the spindle speed are applied. They are divided into three categories as the following : (1) The constant speed 。 (2) The speed spect rum 。 (3) The speed simulating real cutting condition. The effect of the heat generated by the cutting process is not taken into account here. However , the influence of the cutting process on the thermal behaviour of the total machine structure is regarded to be negligible in finishing process. In this machine , the most significant heat sources are located in the zaxis. Thermal errors in z direction on different x and y coordinates are approximately the same. It implies that the positions of xcarriage and ycarriage have no strong influence on the zaxis thermal errors. （ L） Thermal error measurement mounted probe
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