What are the common materials of plain bearings?

Most metal plain bearings are made of bronze.They have the highest load capacity of all three types and are resistant to corrosion.However,they introduce metal-to-metal contact with the shaft,which can lead to wear if proper lubrication is not maintained.Lubrication of bronze bearings must be supplied externally.

Plastic bearings,on the other hand,are self-lubricating.Because they contain no metal surface,they are very resistant to corrosion.However,plastic bearings act as thermal insulators because they do not dissipate heat easily and can deform.They may also expand in the presence of moisture,which can cause friction to be higher than expected.

Composite bearings are typically characterized by metal backing with sprayed or bonded PTFE(Teflon ®)bushing.Aluminum back bearings with PTFE bushing are perfect for straight-line motion applications.Since the bearing surface is PTFE,there is no metal-to-metal contact,and PTFE's self-lubricating properties eliminate the need for external lubrication.Unlike plastic bearings,the presence ofmetal backing also allows them to dissipate heat.The disadvantages of composite bearings are limited speed and reduced ability to handle cantilever loads.

The most important advantages of metal bearings are smaller clearances(i.e. tighter tolerances)and lower initial coefficient of friction (COF).However,they require hardening of shafting,which can be a considerable expense.In addition,certain types of metal bearings can also be corroded.

Plastic bearings,weigh less than other bearing types.They require no external lubrication and are completely maintenance-free.Another key point about plastic bearings is that they can be used in softer shaft materials,which means less weight and lower component costs.While plastic bearings are widely believed to be less robust than metal bearings,the variety of plastic materials offered by bearing manufacturers means that there are plastic bearing options for almost any load or application.One example:plastic bearings can actually perform better when subjected to edge loads or impact loads,which can cause metal bearings to break and fail.

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