Overview

Overview

Today's OEM engineering community has many bushing alternatives to choose. When making a design decision, it can be difficult to compare differences between materials to come to a conclusion which is optimal for your design. An application-driven discussion follows, comparing composite bearings to traditional metallic or thermoplastic bearings.

Use the tabs above to see how composite bearings compare to many common bearing types and materials.

Metal Backed

Metal Backed Bearings

Metal backed bearings have great features and benefits for the price. However, Polygon’s line of PolyLube™ bearings are competitive against this family of conventional bushing materials with recent advances.

Additional Performance Differences:

• With any metal backed bushing, once the overlay is broken into the shaft is in intimate contact with the metal backing–this can result in premature failure.
• Dynamic capacities are typically 20,000 PSI max, vs. 30,000 PSI for a PolyLube Fiber Series bushing.
• As with any metal structure, this type of bushing is subject to severe corrosion–as little as 24 hours into basic immersion testing.

Metal

Greased Metallic Bearings

The most obvious difference? This family of bushing materials requires perpetual greasing. When the lubricating film fails due to contamination, the bushing will prematurely wear. Performance of this bushing is entirely reliant on the end user properly maintaining and servicing the bushing joint in question.

Additional Performance Differences:

• Loads only to 20,000 PSI with lubrication compared to PolyLube™ dynamic loads to 30,000 PSI and static loads of up to 70,000 PSI without lubrication.
• Greased metal-backed bushing materials have very fine operating temperature ranges. They traditionally span from -40 to +210°F compared to PolyLube ranges from ±325°F.
• Once mixed-mode lubrication (grease &/or oil) fail due to particulate ingestion and contamination, this type of bushing can no longer operate successfully.

Rolling Element

Rolling Element Bearings

PolyLube™ bearings are able to handle higher load capacities than traditional rolling element bearings, particularly with shock loading.

Additional Performance Differences:

• Reduce the weight and profile of the bearing–in many cases the weight and profile of the bearing can be reduced by over 50%.
• Higher static load capacities than traditional rolling element bearings–an equivalent sized needle bearing will only have 30% of the static capacity of a composite PolyLube bearing.
• No external lubrication is required with PolyLube bearings–there are no concerns with failed lubrication media resulting in shaft damage.
• By using the PTFE film transfer process instead of macro mechanical moving parts, PolyLube is able to have more predictable performance stability over the life of the application.

Sintered Metallic

Sintered Metallic Bearings

Sintered metallic bearings have innate limitations due to their structure and lubrication mechanisms. Sintered materials dramatically reduce impact or shock loading capability, as well as static and dynamic loading capacities.

Additional Performance Differences:

• At best, dynamic capacities of 8,000 PSI.
• Alloyed bronze bearings have the highest dynamic capacity within this family-and that is 10,000 PSI or less than 5 SFM with lubrication.
• Lowered impact or fatigue strength properties.
• Prone to corrosion and shaft fretting.
• Many times burnishing tools are required to get product to final geometric tolerances.

Filled Thermoplastic

Filled Thermoplastic Bearings

Filled engineering grade thermoplastics have much lower mechanical properties. They also are subject to cold flow, an inherent problem when using any engineered thermoplastic today.

Additional Performance Differences:

• Dynamic and Static Loading Capacities. Engineered thermo-plastic bearing materials exhibit very poor loading capacities.
  PolyLube™ improves this by use of continuous filament reinforcement and a thermoset resin matrix. Thermoplastics are prone to creep under prolonged loading.
• Sizing predictability. Injection molding is prone to variation.
• Impact Fatigue. Even glass filled thermoplastic resins have limits to repeated impact resistance.
• Limited Self-Lubrication Capabilities. Filled thermoplastics have a low lubrication percentage, and PolyLube's PTFE coatings are superior. In-use coefficient of friction and break-in characteristics of each bushing material is different.