| Summary: | 碩士 === 國立勤益科技大學 === 機械工程系 === 102 === Currently, the linear guides have been widely used in high-precision linear positioning stages for CNC machine tools. In the guide modulus, there exits a nonlinear relation between the contact load of rolling elements and the deformation of the ball grooves, which further shows that the contact properties such as the contact stiffness and damping coefficients will change with the preload amount applied on the rolling elements. This will further bring the guide modulus and the feeding stage to behave a different dynamic characteristic. Gaining understanding of the dynamic characteristics of a stage with different preloaded guide modulus is therefore important. This study was aimed to assess the relationship between the preload amount and modal parameters of linear guide modulus, and the effect on the dynamic characteristics of the feeding stage. To this purpose, we used the commercialized linear roller guides with different preload as samples to assess their dynamic characteristics through the vibration tests. The modal parameters such the modal stiffness, modal frequency and modal damping of the guide modulus and the feeding tables were evaluated from the measured frequency response functions, respectively. Also the preloaded amount of each guide module was examined in terms of the dynamic friction measurements. The relation between the modal parameters and the preload of the stage were examined.
According to the experimental measurements, the actual preload of the linear guide modulus was found to deviate from the rated values as setting in factory. This may be due to the assemblage errors of guide modules. For linear guide module, the modal parameters were affected to vary with the change of the preload of the rolling elements. Basically, the guide modulus with higher preload shows a higher natural frequency, but a lower damping property. For the stage with different preloaded guide modulus, the dynamic stiffness was affected by the preload. For feeding stage, the dynamic stiffness in vertical direction at low frequency was mainly affected by static stiffness of the linear guide, which was contributed by its preload, rather than the damping effect induced at the rolling interface. However, the dynamic stiffness in lateral direction was affected by the damping properties, which was contributed by the preloaded amount on the linear guides. This further demonstrates the importance of the selection in the preloaded amount of linear guide modulus.
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