Research On The Heat Conduction Approaches And Control Methods In Grinding Process And High-speed Grinding Motorized Spindle System

High-speed grinding is a development trend of grinding both at home and aboard, which can not only improve the processing efficiency, but also reduce the production costs. There are two key parts which having a great influence on the surface quality and the machining accuracy of work piece.First, the thermal exhaustion problem of the stator used for high-speed grinding motorized spindle system. The stator of the zero transmission synchronous spindle system produces a lot of heat, which affects the machining accuracy especially for the precision machining, due to the thermal expansion of spindle in radial and axial directions.Second, the thermal mechanism during the high-speed grinding process, Numerous heat will be produced during the high-speed grinding process. Most of heat is delivered into the work piece, causing the rise of the grinding arc temperature of work piece surface. Once the temperature exceeds a critical value, the phase constituent of the work piece surface will be changed and affect its performance, even leading to a series of grinding defects, such as grinding burn.Whether the heat generated from the motorized spindle system or the grinding process, it will finally affect the surface integrity and performance of the work piece. Therefore, to find a effective cooling mode for the stator of the motorized spindle system and solve the mechanism of grinding defects will have a great significance.On the base of present literatures, the paper studies the stator surface radiating of the motorized spindle system as well as the past and current situation of the thermal mechanism in high-speed grinding.On the stator surface radiating of high-speed grinding motorized spindle system:1)、Based on the theory of thin-walled cylinder, a computational modeling for the cooling pipes on the stator surface of the motorized spindle system was set up. In addition, the optimal cross-section dimensions as well as the allowable thickness of the slot wall were calculated by the optimization of MATLAB.2)、The impacts of the cross-section dimensions and slot wall thickness of the cooling pipe were analyzed through the thermal analysis software NASTRAN.3、Through the combination of the cross-section dimensions and slot wall thickness, fine cooling performance could be achieved without changing the coolant flow,which provided a design theory for the cooling pipes on the stator surface of the motorized spindle system in actual project.Through the simulation analysis, it was found that the stator surface temperature after optimized was approximately 5 to 10℃lower than before, and further validated that the optimization model was reasonable.On the thermal mechanism in high-speed grinding process:1)、Using theory of equivalent grinding thickness and principle of conservation of energy, the computational modeling to calculate the abrasive dusts with heat flow was set up for cylindrical grinding、internal grinding and plane grinding, This model revealed the density of heat flow delivered into the abrasive dusts with different processing conditions comprehensively,for it involved many principle parameters, such as the wheel speed、the work piece speed and the grinding depth.2)、Through the assumption model of "conical abrasive", the computational modeling used for the effective contact radius of abrasive was acquired, which was in accordance with the actual project. Using this model, the effective contact radius of abrasive under different processing situation could be estimated, which could avoid the drawback of using the same fixed value.3)、Combined the concept of "conical abrasive" with the heat transfer theory, the new model called cross-grain array model was carried out, which was used to calculate the heat transfer coefficients of the grinding arc. This model was designed with the affection of conventional grinding parameters (e.g. he work piece speed), as well as the particle size no. and grain angle.Compared with the grinding case, the enhanced Rowe grinding work piece temperature computing model had the same temperature variation tendency with the one without optimization, and further illustrated the key parameters of the computing model were reasonable.