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| * Effect of Pre-load and Rigidity |
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| The rigidity of a linear system must be taken into consideration when it is to be used in high-precision positioning devices or high-precision machinery. Preloaded slide guides and ball splines, which use a ball as the rolling element, are available upon request to meet the need for greater rigidity. If a force is applied to the ball elements without a pre-load, an elastic deformation proportional to the applied force to the 2/3 power will result. |
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| Therefore, the elastic deformation is relatively large during the initial loading stage, however then becomes smaller as the load increases. The contact angles for all of the ball elements in SGL slide guides are the same as shown in Figure 1-7. Therefore, if the pre-load (P1) applied results in an elastic deformation of δ1, the deformation will vary linearly with the applied load until the elastic deformation of the ball element on the other side cross the race becomes zero, as depicted in Figure 1-8. This permits the determination of the deformation of linear systems. The ratio between the applied load and the elastic deformation is defined as the rigidity of the system. Equation (9) can be used to determine the elastic deformation with an applied load of up to 2.8 times the pre-load. |
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| * Types of Pre-Load and its Specification |
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| Pre-load is categorized into three primary ranges:normal, light, and medium. At NB, pre-load is applied by installing rolling elements that are slightly larger than normal. Therefore, the specification of the preload is expressed by a negative gap value. |
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