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.
This article presents an experimental investigation into the damping characteristics of a linear damper with a newly designed oil groove. The damping performance of the damper is tested in four different viscosity grades by the sweep frequency method. And a test bench is used to move the damper for a several kilometers to examine the damping maintenance. The experimental results show that a higher oil viscosity leads to a higher damping capacity of the linear damper, and the increase in the oil viscosity will improve the damping maintenance of the damper. The newly designed oil groove efficiently improved the damping capacity of the linear damper; a proper oil selection will further optimize the effect of the oil groove via minimizing the oil leakage.
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