Who needs plastic bearings?

Chris Johnson explains five applications where plastic bearings could be your next choice

Hostile. Harsh. Corrosive.  If you’re looking to source bearings for these kinds of environments, then plastic bearings could be the ideal option for your project. But how do you know if it’s time to put the traditional steel bearings to one side and use this alternative material?  

Here are five applications where plastic bearings could be your next choice.

Marine

The marine industry offers a great challenge, due to the ever-present risk of corrosion. Plastic bearings used in the marine industry, depending on the ball and cage materials, can be permanently submerged in seawater.

Acetal resin bearings with 316 stainless steel or glass balls have very good resistance to seawater but can only be used in lower precision, low load and low speed applications.

The speed capacity of plastic bearings can be increased by using an alternative material such as PEEK, but these are still classified as semi-precision, low load bearings.

Food and beverage

The food industry has many corrosive pitfalls for bearings. From sterilising chemicals, to recurring wash-downs, bearings in operation in this sector must contend with a lot.

For applications that are too corrosive for stainless steel bearings, food grade plastic bearings made from acetal resin, polypropylene or PEEK provide an alternative.

Many steel bearings for this industry need to be supplied with non-toxic lubricants approved to NSF (formerly USDA) H1 or H2 standards. These lubricants are also designed to be resistant to washout.

However, plastic bearings can run without lubrication, eliminating the risk of contamination and concerns about washout.

Pharmaceutical or chemical

In the pharmaceutical or chemical industry, acetal resin corrosion resistant bearings cope well with many alcohols and chlorides while polypropylene bearings will offer good resistance to acids and alkalis.

If your application is highly changeable, PEEK bearings can be used in the presence of a wide range of chemicals.

Acetal resin corrosion resistant bearings cope well with many alcohols and chlorides while PTFE bearings will offer excellent resistance to acids and alkalis. If your application is highly changeable, PEEK bearings can be used in the presence of a wide range of chemicals.

Vacuum or cleanroom

Plastic bearings generally operate cleaner than metal bearings because they do not need lubrication to run and do not rust.

Plastic bearings made from PEEK perform well in low load, semi-precision applications in this environment as PEEK is a material with very low outgassing characteristics.

Great care must be taken when choosing bearing lubricant for a vacuum or cleanroom because most greases will vaporise to an unacceptable level, contaminating the environment and preventing the grease from lubricating correctly.

Plastic bearings can also be equipped with special low volatility, perfluorinated greases with very low outgassing rates, which are designed to perform well in highly regulated conditions such as cleanrooms. These greases are regularly used in applications such as semiconductor manufacturing or in equipment used in deep space.

MRI equipment

MRI scanners are high value pieces of equipment that hospitals want to keep running without high maintenance parts. That’s why high-quality plastic bearings could prove crucial in the design of this equipment.

Plastic ball bearings become completely nonmagnetic when fitted with polymer, glass, or ceramic balls. They are ideal for use in MRI X-ray equipment or sensors where there cannot be any magnetic distortion.

Plastic bearings are ideal if you need corrosion resistant, non-magnetic or non-conductive bearings.

Chris Johnson is managing director of plastic bearing supplier SMB Bearings.