Hydrostatic spindles are core components of high precision machine tools, which have been widespread used in mechanical engineering, but the mechanism of rotation error has not been revealed clearly. According to current documents and models, the transient processes of the spindle from an equilibrium position to a dynamical orbit could not be simulated quantitatively. The intrinsic relationship among the disturbance factors, the position, the flow and the oil film force could not be revealed, as resulted in that the mechanism of the rotational error motion of hydrostatic spindle could not be described exactly. The dynamic model of the rotation error motion of hydrostatic spindles is established. Three methods, which are full process moving mesh method, equilibrium position moving mesh method, and equilibrium position simplified formula method, are used to quantitatively calculate the trajectory of a spindle from the concentric position to forming rotational error. The inherent laws among the disturbance factor, total force, the flow and the position are discovered. The rotation error is evaluated by using of the Least squares method. By studying the influence of these three calculation methods on the rotary centre position and rotary error, the reasons that results in calculation difference are found. The method which combines the moving mesh method and the simplified formula to calculate the rotary accuracy of hydrostatic spindle are verified to be efficient and pinpoint.

Study on the Mechanism of Hydrostatic Spindle Rotational Error Motion

Cylindrical grinding is an important way to form the external shape error of the crank journal, and the accuracy consistency directly affects the interchangeability of products. To study the accuracy consistency of crank journal, a dynamic model of the grinding wheel-crankshaft grinding system based on Timoshenko beam is established, and the grinding transition process simulation algorithm with iterative convergence of grinding force-transient grinding amount cycle adapted to the model is proposed, which realizes the simulation of the roundness of the crank journal coupled with the process parameters of the grinding system. Aiming at the grinding position of each crank journal, the grinding roundness of five crank journals is simulated, respectively. On this basis, the crank journal roundness consistency prediction model is established, and the effectiveness of the prediction model is verified by field experiments. Finally, the influence of grinding parameters on the consistency of the roundness of crank journal is studied. The research conclusion can provide a reference for the grinding accuracy consistency design of this type of crank journal. 

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Research on roundness error consistency model for crank journal cylindrical grinding

Crankshaft is a core part of automobile engine to bear impact load and transmit power. Precision grinding is the most important machining method to achieve high precision of crankshaft main journal. Although many scholars have established various simulation models in the field of cylindrical grinding, it is difficult to carry out effective quantitative simulation for a given crankshaft main journal grinding system. Aiming at the shortcomings of the existing models, a double-rotor dynamic model is proposed, which considers the interaction between the grinding wheel and the main journal, and iterative algorithm is adopted to simulate material removal and roundness change in the grinding process of the main journal. The normal force between grinding wheel and the main journal is defined in detail in the algorithm, which is closer to the actual grinding process. For a given crankshaft grinding system, different grinding strategies of the main journal are quantitatively simulated by using the model. The proposed model and algorithm are validated by experiments, which can provide a basic model for the further study of the crankshaft cylindrical grinding system.

Research on double-rotor dynamic grinding model and simulation algorithm for crankshaft main journal

Cooling and lubrication techniques in grinding: A state-of-the-art review, applications, and sustainability assessment

Research on the consistency model of roundness error in journal cylindrical grinding with random parameters

Hydrostatic bearings are the supporting parts of hydrostatic spindles. Hence, the bearing inner bore roundness may affect the spindle shaft equilibrium position and rotation accuracy. Although many scholars have established various models to simulate the internal and external grinding process, the existing models cannot provide precise calculations for choosing an efficient grinding strategy, and the final bore roundness predictions are also insufficient. To achieve precise prediction for grinding process and final bore roundness, the coupling interaction between the grinding wheel spindle system and the workpiece-spindle system during the inner bore grinding process is considered, and then a novel inner bore grinding double rotor model is established. The model adopts iterative algorithm to calculate material removal and the bore roundness forming process. Based on the model, different inner bore grinding strategies are quantitatively simulated for a given grinding system. The material removal and inner bore forming process under different grinding conditions are compared. The final bore roundness roughly matches the experiment results. The proposed double rotor system model and the simulation algorithm could be a new path for further studies of the grinding transition process.

Wanli Xiong

Papers

A novel double rotor coupling model for inner bore grinding process

Research on double-rotor dynamic grinding model and simulation algorithm for crankshaft main journal