IGUS - The 5 Major Benefits of Plastic Bearings

Some engineers hesitate to use plastic bearings in their designs. Maybe because they have trusted metal and bronze bearings for years or they simply don't think plastics can handle the tough applications or environmental elements. Plastic bearings, however, can endure extreme temperatures, heavy loads and high speeds. However, it's important to understand both the advantages and disadvantages of the options available.

Metal-backed, PTFE-based (polytetrafluoroethylene) polymer bearings have a steel backing bonded to a porous bronze sinter layer. The layer is impregnated and overlaid with the filled PTFE bearing lining. This thin lining can be scratched off by contaminates causing metal-to-metal contact between bearing and shaft. This increases the coefficient of friction (COF) causing higher wear rates and shaft damage.

With sintered-bronze bearings, oil is drawn from the bearing as it rotates on the shaft (minimum speed of 1 metre per second). The oil creates a thin film that then separates the bearing and shaft, preventing wear and shaft damage. At high speeds, a low COF is achieved. However, shaft oscillation, slow speeds, irregular use or uneven loads can impede film lubrication from being maintained. As a result, the coefficient of friction and wear rates increase.  This type of bearing should really never be used for linear motion.