數(shù)控機(jī)床相關(guān)畢業(yè)設(shè)計(jì)翻譯---通過(guò)熱量誤差補(bǔ)償來(lái)改善數(shù)控機(jī)床的精確度-數(shù)控設(shè)計(jì)(已修改)
2025-06-01 01:21 本頁(yè)面
【正文】 IMPROVING ACCURACY OF CNC MACHINE TOOLS THROUGH COMPENSATION FOR THERMAL ERRORS Abstract： A method for improving accuracy of CNC machine tools through pensation for the thermal errors is studied. The thermal errors are obtained by 1D ball array and characterized by an auto regressive model based on spindle rotation speed. By revising the workpiece NC machining program , the thermal errors can be pensated before machining. The experiments on a vertical machining center show that the effectiveness of pensation is good. Key words : CNC machine tool Thermal error Compensation 0 INTRODUCTION Improvement of machine tool accuracy is essential to quality cont rol in manufacturing processes. Thermally induced errors have been recognized as the largest cont ributor to overall machine inaccuracy and are probably the most formidable obstacle to obtaining higher level of machine accuracy. Thermal errors of machine tools can be reduced by the st ructural improvement of the machine tool it self through design and manufacturing technology. However , there are many physical limitations to accuracy which can not be overe solely by production and design techniques. So error pensation technology is necessary. In the past several years , significant effort s have been devoted to the study. Because thermal errors vary with time during machining ,most previous works have concent rated on realtime pensation. The typical approach is to measure the thermal errors and temperature of several representative point s on the machine tools simultaneously in many experiment s , then build an empirical model which correlates thermal errors to the temperature statues by multivariant regression analysis or artificial neural machining , the errors are predicted online according to the preestablished model and corrected by the CNC cont roller in realtime by giving additional signals to the feeddrive servo , very few practical cases of realtime pensation have been reported to be applied to mercial machine tools today. Some difficulties hinder it s widespread application. First , it is tedious to measure thermal errors and temperature of many point s on the machine tools. Second ,the wires of temperature sensors influence the operating of the machine more or less. Third , therealtime error pensation capability is not available on most machine tools. In order to improve the accuracy of productionclass CNC machine tools , a novel method is proposed. Although a number of heat sources cont ribute to the thermal errors , the f riction of spindle bearings is regarded as the main heat source. The thermal errors are measureed by 1D ball array and a spindlemounted probe. An auto regressive model based on spindle rotation speed is then developed to describe the timevariant thermal error. Using this model , thermal errors can be predicted as soon as the workpiece NC machining program is made. By modifying the program , the thermal errors are pensated before machining. The effort and cost of pensation are greatly reduced. This research is carried on a JCS2020 vertical machining center. 1 EXPERIMENTAL WORK For pensation purpose , the principal interest is not the deformation of each machine ponent , but the displacement of the tool with respect to the workpiece. In the vertical machining center under investigation , the thermal errors are the binati
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