Thermal expansion error modeling and compensating method for semi-closed-loop feed shaft under excitation of multi-time-varying dynamic heat source

Abstract

The invention provides a thermal expansion error modeling and compensating method for a semi-closed-loop feed shaft under the excitation of a multi-time-varying dynamic heat source and belongs to the field of numerical control machine tool error compensation. The generation mechanism of heat by friction, the heat conduction mechanism and the heat convection mechanism, under the excitation of a multi-temporal and variation-dynamic heat source, are analyzed. According to the superposition principle of the temperature field, a temperature field prediction model under the excitation of a nut pair time-varying dynamic heat source and a temperature field prediction model under the excitation of a bearing seat time-varying dynamic heat source are respectively established. Through integrating a discrete screw temperature field at any time, the predicted value of the real-time thermal expansion error of a screw can be obtained. The predicted value of the thermal expansion error of the screw is written into a numerical control system in real time, and then the thermal error of a feed shaft can be compensated. The above model records the dynamic change process of the discrete temperature field of the feed shaft, namely the change of the motion state of the feed shaft. Meanwhile, the good compensation effect is still realized. The above method is high in prediction accuracy, and is strong in robustness for the change of the motion state.

Description

technical field [0001] The invention belongs to the technical field of error compensation of numerical control machine tools, and specifically relates to a thermal expansion error modeling and compensation method of a semi-closed-loop feed shaft excited by multiple time-varying dynamic heat sources. Background technique [0002] The thermal error of machine tools has been a problem that has plagued the machine tool industry for decades. Due to the existence of machine tool thermal errors, the problems caused are: the processing accuracy of a single piece is easily unqualified; the consistency of batch processed parts is poor, and the scrap rate is high; The machining accuracy requirements are high, and high cost is required to build a constant temperature workshop. These issues illustrate the many adverse effects that thermal errors can have on machine tools. [0003] At present, there are two main methods to reduce the thermal error of the machine tool: the error preventi...

AI Technical Summary

Problems solved by technology

Due to the existence of machine tool thermal errors, the problems caused are: the processing accuracy of a single piece is easily unqualified; the consistency of batch processed parts is poor, and the scrap rate is high; The machining accuracy requirements are high, and high cost is required to build a constant temperature workshop

In 2015, W.L.Feng et al. published the article "Thermally induced positioning error modeling and compensation based on thermal characteristic analysis" in Volume 93 of "International Journal of Machine Tools & Manufacture", which analyzed the heat transfer process of the lead screw in the heating and cooling stages and established the temperature rising and the thermal characteristic model in the cooling stage, which solves the problem of thermal error prediction of the lead screw in the state of uneven heat distribution, but does not consider the influence of multiple heat sources

[0007] Through the analysis of the current research status, none of the above patents and papers mentions the semi-closed-loop feed shaft thermal expansion error modeling method based on frictional heat generation, heat conduction and heat convection mechanisms, nor does it consider the nut pairs, bearing housings, etc. Temperature Field Prediction Model Excited by Multiple Time-varying Dynamic Heat Sources

Images