Papers by Author: Yi Lei Liu

Abstract: Volumetric error has large effect on machine tool accuracy; improving CNC machine tool accuracy through error compensation has received significant attention recently. This paper intends to represent volumetric error measurement based on laser tracker. The volumetric error is modeled by homogenous transformation matrix with each coordinate corresponding to each motion axis. Based on parts of spatial points volumetric error, the geometric errors which affect volumetric positioning error are verified through particle swarm optimization with the L₂ parameters as the target function. The chebyshev orthogonal polynomials are applied to approximate geometric errors.

Abstract: Thermal error of machine tool is the main in total machine tool error, and obviously impairs the accuracy of the machined workpieces. Ram is a very important component of heavy-duty floor type boring-milling machine, and its thermal deformation is a significant source causing errors in machining process. Aiming at the thermal elongation of heavy type milling boring machine tool ram, the machine tool thermal errors are measured and compensated. Temperature compensation function in NC system is applied. Experiment results shows that 90% ram positioning error can be compensated.

Abstract: Ram is a very important component of heavy-duty floor type boring-milling machine, and thermal deformation is a significant source causing errors in machining process. The law of thermal deformation of ram is researched for real-time compensation for thermal deformation error of ram. Meanwhile, DRF function compensation is proposed based on 840D NC system. Real-time error compensator is made and proved to be available by experiment.

Abstract: Guide ways of ultra-precision machine tools always have sufficient stiffness and guiding precision. But guide way rails deformation caused by oil film pressure and slider offset lead to oil film clearance change which affects static stiffness and guiding precision. An inside-slider hydrostatic guide way is designed, and its static characteristics are analyzed. As a result, the effect of slider offset on stiffness and guiding precisions is obtained. A FE model of guide way is established. An elastomer of virtual material properties is used to simulate oil film, so that the relationship between oil film clearance and pressure can be represented in a certain range. Static stiffness and guiding precision are obtained considering deformation of rails.