Effect of surface topography of scraped machine tool guideways on their tribological behaviour

Abstract

Tribological behaviour of two kinds of scraped surface topography of machine tool guideways — the conventional form named ‘narrow-deep’ scraping and an improved form termed ‘wide-shallow’ scraping — is described. Behaviour is compared under the following conditions: average pressure p = 0.135−0.675 kgf cm −2 and sliding velocity V = 15−600 mm min −1. In comparison with narrow-deep scraping of slideways, wide-shallow scraping may reduce the friction coefficient by about 50–90%, relieve the phenomenon of stick-slip, and increase the amount of table floating. Consequently, the positioning accuracy of the machine tool feed drive system and the wear durability of guideways can be expected to be improved greatly. The amount of scraping work might be decreased to less than 1 2 . An attempt is made to explain the above results from the viewpoint of hydrodynamic lubrication and to summarize the characteristics of the two kinds of scraped surface mentioned above. Based upon a series of experiments, the authors propose that in evaluating the performance of guideway surfaces, the concepts of oil-film-forming ability and oil-film-retaining ability are helpful.