A linear model for the machine tool assembly error prediction considering roller guide error and gravity-induced deformation

In assembly, error prediction and control according to the error state of the machine parts are the key links to ensuring the accuracy of the entire machine tool. In this study, an assembly error modeling method considering the error of the roller guide and gravity-induced deformation is proposed. First, based on the Hertz contact theory, a nonlinear error propagation model for the roller guide to the moving part is proposed. With this model, the analytical relationship between the straightness error of the guide rail and the errors of the moving part can be established. Then, after the linearization of the guide error model, a machine assembly error model considering the guide error is proposed. This model expresses the linear relationship between the error of the rolling joint surface and the error of the machine tool after the final assembly. Additionally, considering the influence of gravity deformation of structural parts, the gravity deformation is extracted by the finite element analysis method and added to the model by linear superposition. As a result, the model corresponds more with the practical assembly process. Finally, an assembly error prediction method of the precision horizontal machining center is presented, and a case is studied to demonstrate the validity of the proposed model and method.

Modeling of Static Stiffness for Linear Motion Roller Guide

The purpose of this study is to investigate the modeling method of static stiffness for the linear motion roller guide (LMRG) with five degrees-of-freedom (5DOF). The model of static stiffness for the LMRG with 5DOF was established using the slicing method, the guide deformation compatible equation, and the force equilibrium equation of the guide. The static stiffness of the LMRG was analyzed systematically via a case study, and the simulating results were verified by the experimental data. The results show that the proposed model can be used to calculate the complete static stiffness for the LMRG with 5DOF.

Improved design of roller linear guide for heavy load based on finite element method and measurement

Roller linear guides are key components in machine tool. The accuracy and efficiency of a machine toll are determined by the stiffness and friction torque of roller guide. This study proposes an improved design method for roller guide. The influences of the rollers profile on stiffness, stress distribution of roller linear guide are analyzed using finite element simulation. In this work, the design of the roller, slider, and the overall structure is modified. Moreover, experimental investigations on noise and sliding friction of roller linear guide are compared to validate the proposed design method. It seems that the proposed design can improve the dynamical performance of the roller linear guide.

Real contact total length of linear motion roller guide without preload based on Greenwood–Williamson rough contact model

In traditional studies of linear motion roller guide, the static stiffness is a main indicator to evaluate the mechanical behavior. However, the local contact profile between the roller and raceway surface, although very important to the precision maintenance, cannot be reflected in the measured value of static stiffness. In this article, a new indicator, named the real contact total length (RCTL), is proposed based on the Greenwood–Williamson model and the Hertz contact theory. In particular, an electric contact model is presented where the RCTL of linear motion roller guide without preload is expressed in terms of the measured electric resistances. To verify the model, an experiment is conducted to measure the electric resistances under different vertical loads by a designed load test bench and a digital, direct-current, high-resolution electric resistance meter (DRRM). The test results show good agreement with the model. Based on the electric contact model, the main parameters that affect the RCTL value are roughness Ra and the length of roller, which are directly related to the mechanical behavior of linear motion roller guide in the design and manufacture stages.