Active coolant control onto thermal behaviors of precision ball screw unit

Abstract

Being a critical factor affecting the motion accuracy of precision machine tools, structural thermal elongation of precision ball screw unit is generally caused by the comprehensive influence from heat generations of screw-nut pair / bearings and time-varying ambient temperature.To resist 2 thermal disturbances above to guarantee precisely the original length of screw shaft, an active coolant control strategy is proposed in this paper. This strategy is based on an empirical model: For the slender and long tubular structure of screw shaft, the screw shaft temperature is approximately equal to its recirculating coolant temperature. The reason is that the intensive forced coolant convection is capable of eliminating screw shaft temperature rises caused by friction heat generations and ambient air convections. Based on this premise, screw coolant temperature can be consistently controlled by an active strategy, further to correct the thermal elongation of screw shaft.It can be experimentally verified that the thermal variations of machine positioning accuracy caused by the active coolant control strategy are not more than 10μm, which are lower than traditional strategy. Besides, based on detected structural temperatures of precision ball screw unit, the empirical model above is further proved to be reliable by FE simulation method.

XGBoost-based thermal error prediction and compensation of ball screws

“…The thermal elongation correction of ball screws was validated by researchers using various cooling systems, including air, 4 liquid, 5 oil, 6 and circulating coolant system. 7 Gao et al applied carbon fiber-reinforced plastic 8,9 and graphene 10,11 to ball screws to improve positioning accuracy. Even though the effectiveness of suppression methods has been validated, their weaknesses should be focused on.…”

Dynamic properties analysis of ball screw feed system based on improved hybrid model

“…As the most common machine tool feed system, the motion control accuracy of ball screw directly determines the machining accuracy of machine tool [1]. At present, the main method of research on ball screw feed system control technology is to establish a control model and analyze the system dynamic properties according to the model, and then design a controller to meet the control requirements according to the dynamic properties of the system.…”