Study on Comparison of Friction Force between Ball- and Roller-LM Guides

The linear motion guideway (LM guide) is one of the key parts of precision motion and positioning, and it requires high straightness, form accuracy, stiffness, and surface quality. LM guides are actively used in manufacturing facilities for automobiles, aerospace, optics, semiconductors, robots, displays, and portable communication equipment. At present, most of LM guides are based on rolling contact, using either balls or rollers. Roller LM guides have been in high demand in recent years in various industrial fields that require high rigidity. In this study, the friction characteristics of ball and roller LM guides with the same rail width were compared, and friction behavior was analyzed. An experimental setup consisting of a driving unit, specimen, force sensor, and signal acquisition unit was constructed, and signals were collected under various conditions. Three lubrication conditions were used: no lubrication (dry surface), ISO-VG 32, and 68, and a wide feed-rate range from 1 to 100 mm/s was selected. The experimental results showed that the ball LM guide and the roller LM guide had significantly different friction characteristics, which were analyzed from the aspect of Stribeck curve components. In conclusion, friction behavior differed according to lubrication conditions in the no-payload state of the ball and roller LM guides, and the effect of lubrication conditions on friction behavior was shown.