Gas bearings are rarely used, but broadly speaking, guideways are also called linear bearings, and gas floating guideways are still relatively common. The purpose of bearings is also to provide support while reducing friction. So there are two basic key elements, one is the bearing stiffness and the other is the coefficient of friction. In most cases, of course, people want the greater the bearing stiffness the better, and the smaller the coefficient of friction the better, but the reality is that it is always difficult to have it both ways. Generally speaking, bearings can be divided into five categories.
bearings can be divided into five categories
Air-bearing guides, hydraulic bearings, ball bearings, roller bearings and plain bearings. From left to right, the coefficient of friction gradually increases, but at the same time the support stiffness also gradually increases.
Ball bearings are the most widely used and most common. However, for the requirements of precision positioning occasions, such as three-coordinate machines (resolution of 1um large stroke three-dimensional precision measuring instruments), friction caused by the jump when the sliding phenomenon will lead to the inability to precise positioning, when it is hoped that the friction is as small as possible, so the use of air floating guide design. On the contrary, for some occasions requiring high support stiffness, such as cylindrical grinding machine tools, the grinding wheel axis is subject to a large transverse grinding force, and fluctuates greatly in processing, if the support stiffness is low, it will inevitably lead to the centre axis of the grinding wheel wobble offset, when the workpiece will be ground out of round. Therefore, many precision grinding machines will use sliding bearings (commonly known as shingle bearings), where the inner and outer layers of the bearing are rubbed directly against each other with a wear-resistant layer for sliding type friction.
