iglidur® - Coefficients of friction

iglidur® bearings have the self-lubricating property due to the solid-lubricant additives. The solid lubricants lower the coefficient of friction of the bearing and thus support the wear resistance. The coefficient of friction, specifically the friction coefficient µ, is proportional to the normal force and states which force should be applied to move a body against another. Depending on whether a body moves from a position of rest, or maintain the already existent motion, one differentiates between the coefficients of static friction and gliding friction.

The connection between coefficients of friction and surface finish of counter partners is interesting. Here it can be clarified that the friction is a product of various components.

If the counter partner is too rough, abrasive operations play a significant role. Small unevenness of the surfaces that tend to get stuck must be removed. If the surfaces are too smooth, there occurs higher adhesion, which means the surfaces positively stick to each other. Higher forces are then required again for their overcoming, a result of the increased coefficient of friction. Stick-slip effect can be the consequence of a great difference between static and gliding friction and a high adhesive tendency of gliding pairs. It arises by bumpy running behavior and can become noticeable with a loud squeaking noise. One can observe time and again that such noises can be stopped or eliminated with coarser shafts. For applications with a particular tendency toward stick-slip – slow movements, strong resonances of the housing – the ideal surface finish (coarseness) of the shafts should be considered.