| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 103 === Hard rails are usually employed for feeding system of heavy load and heavy-duty machine tools. While hard rail requires lubrication on the contact surfaces scraping is applied to allow lubricant flow into the interface. However, the characteristics of such feeding system is hard to control because of the quality of manual scraping varies depending on the craftsmen’s skill as the technique is inherited between masters and apprentices. Previous studies have revealed that friction characteristics are can be improved micro-structure textures fabricated on the friction surfaces by computer numerical controlled machining. However, the friction characteristics of such texture are not consistent, found from characteristic tests. This study is to design and to fabricate a new texture to improve the stability of friction characteristics in the reciprocating motions of feeding system.
The major results achieved in this study can be summarized as follows. (1) Results of pilot experiments showed that the friction coefficient, based on previously designed textures, of forward and backward strokes are different in the reciprocating motion. (2) The friction characteristics of three types of manually scrapped blocks are close to that of manually scraped hard rail of a machine tool. The result showed that the friction coefficients of forward and backward strokes are stable, unless under the condition of low velocity and low pressure. (3) A new texture with new configuration of grooves is designed and tested. The results showed that the friction coefficient of the new texture is about the same as that of manual scrapping, in both value and stability.
The results of this study revealed that, by comparison with manual scraping, the friction properties of the sliding blocks with new texture are on the same level. While the texture is machined by CNC machining, the quality and repeatability can be well controlled that overcomes the major drawback of manual scraping. This study also reveals that current manual scraping of hard rails can be replaced by this technology with better quality.
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