| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 102 === Slideway of a machine tool often employ hard rail, i.e. sliding contact instated of
rolling contact, for its feeding system in particular for heavy-duty machines. While
hard rail requires lubrication on the contact surface, manual scraping is the most
commonly used approach to improve the friction characteristics as the scraped surface provides channels for lubricant to spread over the surface. However, manual
scrapping is an inherited craftsman technique that led the quality of scrapping highly
depends on craftsmanship and results in incapable of controlling the performance of
sliding surface. Based on fluid dynamics, this research developed a micro-structure
texture, which can be fabricated by computer numerical controlled machining, on
sliding surface as a replacement of manual scrapping. Frictional performances of
these designed hard rails with micro-scale texture are further measured in a feeding
system to verify its feasibility.
The results of this research can be summarized as follows: (1) The friction
coefficients of the developed hard rail with micro texture are between 0.04 and 0.05,
under surface pressure from 0.8 to 2.3 kgf/cm2 and velocity from 1200 to 4200
mm/min, which outperforms current industrial practice by manual scraping; (2)
Surface texture with transversal grooves at the front provides better flowability for
lubricants that results in less friction; (3) Surface texture with grooves passed through multiple dimpled oil cavity provides better frictional characteristics as the lubricants can rapidly flow into the dimpled cavity that reduces the friction; (4) Although the Turcite-coated surface gives higher friction, the friction coefficient keeps stable as the sliding velocity increased.
The results in this research showed that the newly developed non-scraping hard
rail provides better frictional performance than those with manual scrapping in current machine tool industry. Moreover, this developed hard rail can replace manual
scrapping to improve the quality and the machining efficiency.
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