Improvement of temperature accuracy in oil cooler systems with gas bypass

Abstract

In keeping with the development of machine tools with higher speed, more axes, and a greater degree of sophistication, thermal deformation is becoming an important factor in the precision of machine tools. It has been found that thermal error accounts for about 70% of the total error in machine tools. As such, oil coolers which absorb heat from heat generating parts with cold oil are being used to reduce the error caused by thermal deformation. The gas bypass type oil coolers used in ultra-precision (temperature accuracy within ±0.1°C) machine tools are simple in structure and precise in terms of their temperature control performance; however, they have a limitation as regards temperature control due to the instability of their performance under light load conditions. In this study, an oil cooler system equipped with dual electronic valves was developed to solve the problems of the single electronic valve system and achieve more precise temperature control. To verify the performance of the developed system, its performance under the operating conditions of rated load, DIN 8602 standard, and ISO/DIS 230-3 operational mode was compared and analyzed. The proposed oil cooler system is applicable to semiconductor equipment, ultra-precision injection molds, and ultra-precision machine tools, and improves the quality of the products.