Étude sur les dommages des embouts coulissants en plastique
Date de sortie：2008-06-23 Total des Hits：472
While the abrasion resistance of plastic sliding bearings is chiefly determined by the wear resistance of the bearing materials, the wear of plastic sliding bearings is closely connected with the following factors: material of the grinding axis, hardness, roughness, bearing operating speed, load, and ambient temperature and humidity, etc. As a manufacturer of plastic sliding bearings, CSB is constantly striving to improve the abrasion resistance of plastic sleeve material, and provide users with correct selection information. Users should consult sliding bearing selection and fitting instructions in the plastic sliding bearing manufacturer's product handbook.
The key moment for all sliding bearings is when they begin to move.
At this time, the bearing begins to operate before the lubricating film is formed, this is the most common situation.
Whenever a bearing must operate under a load, the bearing will suffer small amounts of wear.
During the start-up stage, when micro-wear is relatively great, the particles resulting from micro-wear will adhere to the surface of the shaft, which will create an optimal lubricating film when in low-wear operation.
After start-up, micro-wear will decrease quickly, and this effect is almost independent of size.
During continuous operations after the start-up phase, the wear rate will be low and steady.
All types of plastic sliding bearings have their own optimal working conditions, including optimal shaft material, roughness, working pressure, rotational velocity, and temperature. For instance, in the case of CSB-EP series plastic sliding bearings, the optimal shaft type has a hard chromium-plated surface. In addition, different types of CSB plastic sliding bearings have different shaft roughness requirements, and we can see from Fig. 3 that the roughness requirements of CSB plastic sliding bearings range from Ra0.1 to Ra1.6. The optimal operating temperature of CSB-EPB5 plastic sliding bearings is not room temperature; instead, the EPB5 bearings offer optimal frictional wear performance at a temperature of 160°C.
After simulating various types of operating conditions, CSB's laboratory has found that the wear on plastic plain bearings takes the following forms:
Normal wear - Wear occurred during normal operation conditions. In these circumstances, bearing wear occurs mostly during the start-up stage when the lubricant from the bearings migrates to the surface of the grinding axis. After the optimal lubrication conditions have been established, the rate of bearing wear will gradually decrease.
Creeping wear - The fact that the shaft surface is too smooth induces friction surface creeping. If the shaft surface is too smooth, lubricant matter from the plastic sliding bearings cannot migrate to the surface of the shaft, fill pits in the shaft, and form a lubricating film. This will prevent the establishment of an optimal friction couple. The bearing's coefficient of friction will therefore increase, and the driving force will increase with it;
Furrow wear - A shaft that is too rough will cause furrow-like scratches in the friction surface. Because the height differences in the shaft surface are too great, the lubricant matter migrating from the bearing surface cannot form an optimally smooth friction surface, and wear in the form of scratches will occur;
Adhesion wear - Occurs when the bearing's safe operating temperature is exceeded or a bare shaft causes adhesion. When a bearing exceeds its acceptable safe operating temperature, the bare shaft will stick to the partially softened bearing friction surface, causing wear.
Burn wear - An excessive operating speed may cause burn wear of the friction surface. If a bearing's operating speed exceeds the acceptable operating speed, this will cause friction and heating of the friction surface, and the abrupt increase in heating may result in burning of the friction surface.
Of course somewhere of plastic sliding bearings is an inevitable phenomenon. When the performance of plastic sliding bearings has been specified, we can only try to comply with the use recommendations of the bearing model as much as possible in order to minimize bearing wear and achieve the best possible performance from plastic plain bearings.