CNC machine tools has made necessary the rapid response of slides to a command signal and constant frictional resistance to slide movement is desirable. The phenomenon gives rise of the familiar stick of oil is lubricated sliding surfaces when the adjustment is needed or jerky action when movement takes place at low velocities, the term stick-slip is used to describe these situation.
To overcome these problem of stick-slip CNC machine use
· Anti-friction bearing elements like re-circulating roller packs, re-circulating ball bushing or
· Non metallic liners like Pol Tetra fluro Ethylene [PTEF], Turcite-B and Ruion being very commonly used or
· A combination of anti-friction bearing elements and nonmetallic liners which provide low friction and necessary damping or
· Hydro-static or Aerostatic slide ways
Advantages of friction guideways
· Used on conventional machines
· Low manufacturing cost
· Good damping properties
· Do not possess constant coefficient of friction
· Problem of stick slip occurs
· Can not be Preloaded
· Guide ways are integral part of structure and hence can not be replaced
· Turcite / PTFE lining to reduce stick slip.
Examples of friction guideways
V guide way : self aligning
Flat guide way : better load bearing capability
Dovetail guide way : compact
Cylindrical guide way : ideal for shorter traverses
