One of the chief difficulties in traditional bushing design is lowing friction and preventing premature wear, despite lubrication. This lifecycle concern comes as no surprise given that efficient machines run around the clock and typically produce varying degrees of heat profiles within the operating systems. A secondary lubrication source, such as a costly grease or oil, should be avoided but may need to be considered to help manage the destructive heat influences.
A bushing designer can work on the problem by analyzing the source of the wear and examining parts that show signs of high wear and heat discoloration. Many times wear elimination can be as simple as avoiding metal-on-metal contact between the interfaces, pin and bushing. By adding a polymer between these surfaces, wear and friction can be controlled. Keep in mind the absence of a lubricant can still lead to failures in a very short period of time and subsequent frequent maintenance.
A less obvious source of wear emerges from the lack of secondary lubrication that can control run-a-way heat. Adding a thermoplastic polymer liner with grease/oil will oftentimes solve the problem associated with metal on metal bearing failure.
Metal-polymer bushings have a similar structure to the PTFE-based materials that are used in dry service conditions. With this technology, the bushing liner consists of a filled or unfilled thermoplastic interlocked as a thin wear-resistant layer for the shaft to run against efficiently.
These Metal-polymer based bushings are generally designed to operate with marginal lubrication and extend service life. They are commonly offered with a uniform dimple pattern of indents in the bushing poly-surface, which act as grease reservoirs. Applications where medium/high loads and high oscillations force friction to spike and wear on parts are the ideal fit for these bushings. This technology is able to withstand varying temperatures and have high load-bearing tolerances.
The Bottom Line
Metal-Polymer bushings are suitable for linear, oscillating and rotating movements.