Temperature distribution and thermal error prediction of a CNC feed system under varying operating conditions

Abstract

In high-speed and high-precision feed systems, the thermal errors are mainly caused by the non-uniform temperature variations and time-varying thermal deformations under different operating conditions. The research work undertaken herein ultimately aims to develop a generic method which is capable of evaluating the temperature rises of heat sources (such as supporting bearings and ball screw nut) and thermal positioning error of the feed system induced by varying operating conditions (feed speed, cutting load, and preload of ball screw). Experiments were carried out on a high-speed feed system experimental bench, and the influences of operating conditions on temperature rises of supporting bearings and ball screw nut were analyzed. Based on wavelet neural network and NARMA-L2 model, the relationship between temperature rise of supporting bearings and operating conditions was established. Furthermore, with the temperature of ball screw nut set to be a moving heating source load, the temperature and thermal deformation distributions of ball screw under bearings and ball screw nut heat sources were simulated. The experiment and simulation results show that the recommended modeling method can be used to predict thermal positioning errors of feed system with good accuracy. The work described lays a solid foundation of thermal error prediction and compensation in a feed system under varying operating conditions.

Actualities and Development of Heavy-Duty CNC Machine Tool Thermal Error Monitoring Technology

“…Some researchers [4,48,49] developed the FEM model for the screw, in which the strength of the heat source measured by the temperature sensors was applied to the FEM model to calculate the thermal errors of the feed drive system. Jin, et al [50][51][52], presented an analytical method to calculate the heat generation rate of a ball bearing in the ball screw/nut system with respect to the rotational speed and load applied to the feed system.…”

Time-varying thermoelastic coupling analysis of heat source of ball screw feed drive system

“…The temperature eld is the external expression of the thermal characteristics, and building the temperature eld model is one of the purposes of studying the thermal characteristics of the ball screw. Jin et al equivalent the ball screw to a cylindrical shape, and built the temperature eld model by heat transfer equation, nite difference method, uniform heat ux applied on the surface and other methods [15][16][17][18]. The simpli ed method makes the theoretical analysis and nite element analysis simple, but ignores the real form of the heat source of the screw nut pair, and the temperature eld obtained has a large error with the real solution.…”

Influence of external heat sources on volumetric thermal errors of precision machine tools

“…EHSs are mainly attribute to the environment in which the machine tool is installed and they affect machine tool through convection and thermal radiation. Most of the studies focus on machine tool internal sources analysis [5][6][7][8] while studies concerning the influences of EHS on machine tools are insufficient. However, the impacts of EHS are non-negligible, especially for thermal sensitive precision machine tools.…”