Thermal characteristics analysis and error prediction for lubricated multi-link high-speed precision presses

Abstract

Thermal models are important in the process of predicting the thermal characteristics and corresponding thermal error of multi-link high-speed precision presses (MLHSPPs) with an oil-lubrication system. Previous models only involved the effects of bearing stiffness, temperature change of bearings, flexibility of crank shaft on the heat generation power, while the influences of revolute clearance joint and flexibility of linkage are seldom considered, which inevitably reduces the accuracy of thermal analysis. To overcome this problem, dynamic models of flexible multi-link mechanisms (MLM) with clearance, lubrication, crankshaft-bearing system are constructed, the interaction forces between pin and bushing are obtained to calculate its heat generation power. Then, an improved model of MLHSPP with lubrication is proposed to analyze the temperature evolution and the thermal error between slider and work table at the position of LDP, by considering bearing stiffness, temperature change of bearings, flexibility of crank shaft, linkage, clearance, lubrication and thermal contact resistance all together. Compared with results from traditional models, the simulation data from this improved thermal model agree well with experiment, which proves the validity of the proposed model. Furthermore, the temperature rise and the thermal error of MLHSPP between slider and work table at the position of LDP under different input speeds, lubricating oil flux and contact angles of ball bearing were also studied.