Plain bearings are used in products across industries, and many of those bearings are manufactured from metals. While metal may be a viable choice, in many cases, engineering plastics may be better because today’s modern plastics are designed to handle challenging applications and severe environments.
What are Plain Bearings?
Plain bearings operate on the science of tribology – technology of interactive surfaces in relative motion. Plain bearings are used to reduce friction or support relative motion between two surfaces. Unlike rolling element bearings, plain bearings have no rolling components, like balls or rollers, and are designed from solid material. There are several reasons why plain bearings are preferred to rolling bearings, including cost, predictable life cycles, non-catastrophic failure (no balls or rollers to shoot out), and higher load capacity by size.
Plain bearings operate under a load, and the two surfaces rub together to create friction. To lower the coefficient of friction and reduce wear, lubrication is required. For metal bearings, this is typically a grease. For engineered plastics, the components may be self-lubricating or contain graphite.
There are five types of plain bearings:
- Sleeve bearing function via a slide motion and support linear, oscillating, or rotating shafts.
- Flange bearings operate in rotary and linear motions and have a flange for axial guidance.
- Thrust bearings (or washers) are flat and prevent metal-to-metal contact in thrust load applications.
- Spherical bearings are self-aligning and allow angular movement to compensate for shaft misalignment.
- Pillow block bearings are mounted units that offer alignment flexibility.
Why Convert to Engineered Plastic?
While bearings may be a small component of your part, they play a significant role in its functionality and, in some cases, safety. It is reasonable to be hesitant about converting your metal bearing to plastic. Working with a plastic manufacturer with extensive polymer and bearing and wear product experience will ensure the transition products have a bearing that meets all functional, environmental, and safety requirements.
While there are many benefits for using plastic plain bearings, common ones include:
- Weight reduction
- Corrosion resistance
- Wear performance improvement without lubrication
- No maintenance
- Coefficient of friction consistency throughout life
- Noise reduction
- Insulating properties
- Part-life longevity
- Predictable end-of-life
- Design flexibility
- FDA, USDA, and 3A sanitation-compatible materials available
When designing a plain bearing, there are a variety of resins they can be made from, including filled resins. For those not wanting to walk away from metal completely, steel-backed, composite-lined bearings may be an option. The choice will depend on the application. Bearing design isn’t about finding a material that can work across all bearings but tailoring it to the application based on costs, performance, and maintenance.
The primary considerations for designing a plain bearing are the pressure (P) or the load on the bearing and the velocity (V) the two surfaces are traveling against each other. Together, referred to as the PV limit, the load and velocity create frictional heat. Each polymer has a maximum PV limit, as well as a maximum pressure and velocity limit. Evaluating all three is necessary. In addition, each material will have a continuous service temperature, which also must be considered.
Ensinger Precision Components Plain Bearing and Wear Products Experts
When you are ready to convert from metal bearings to engineered plastic plain bearings, we are prepared to help. We specialize in self-lubricating, low-cost, and long-lasting plain bearings and wear components with more than five decades of combined experience creating bearings for real-world applications. We will customize your plain bearings to suit your application, but if a standard plan bearing works for you, we have them, too. Our objective is to ensure the material choice will minimize the bearing’s maintenance and maximize its wear life. Many engineers specify our plain bearings because they are cost-efficient, simple in design, and can handle high loads in aggressive environments.