A comparison of different bearing types

Plain bearings with lubrication grooves are made from a solid material. They are often made of steel, bronze or other metals. These bearings obtain their sliding properties from lubrication channels or lubrication grooves that are incorporated into the surface of the bearings. These channels allow the lubricating grease to be distributed more evenly throughout the entire bearing. However, this also means that the bearing must be permanently lubricated. Solid plain bearings can withstand high loads and are therefore often used in larger bearing points. However, due to the complex machining and solid material, they are also comparatively expensive.

Advantages

• High load capacity
• Protection against corrosion and dirt when lubrication is maintained
• Lubrication grooves ensure distribution of lubricant

Plastic plain bearings – design and function

Plastic plain bearings are often injection-moulded components or manufactured from solid plastic bar stock. 3D printing and laser sintering are also common manufacturing methods. Many plastics are suitable for use in plain bearings. Depending on the type, they also have other specifications, such as high chemical resistance or resistance to high temperatures up to approx. 300°C. Since these plastics are in granulate form before processing, they can be mixed relatively easily with other additives such as solid lubricants, fibres or fillers, as well as additives. This material mixture is then melted during the processing stage. This results in components whose specifications exceed those of the plastics originally used. This allows for the production of very strong, exceptionally smooth-running and self-lubricating plain bearings.

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Advantages

• Consistent sliding properties across the entire wall thickness
• Weight savings compared to metal bushings
• Self-lubricating  and maintenance-free
• Chemical and media resistant
• Wide range of shapes possible
• Very low space requirement
• Insensitive to dirt
• Cost-effective

Sinter bearings are named after the way they are manufactured. They usually consist of bronze powder that is compressed under high pressure and high temperatures. This process is called sintering. Due to the grain size of the powder, the bearing has pores after manufacture. The bearings are soaked in oil, which then settles in the pores. During use, the oil in the sintered bearing is heated by frictional heat, becomes more fluid and is thus released from the pores. The bearing point must therefore be lubricated. Sintered bearings are relatively cost-effective and, due to their mode of operation, are particularly suitable for bearing points with higher rotational speeds and less suitable for slow pivoting movements.

Advantages

• If the bearing point is correctly designed and constructed, the bearing is maintenance-free.
• During movement, the lubricant is released and "stored" again when the bearing is at a standstill.
• Robust and pressure-resistant.

Fibre composite plain bearings – structure and function

In fibre composite plain bearings, fibres made of glass, carbon, cotton or plastic are woven together, combined with synthetic resins and other additives, and compressed under high temperatures and pressure. This creates extremely resilient bearings whose strength can even match that of metal bearings, depending on the type of load. Different winding and weaving techniques can also be used to create different layers, which in turn have different specifications. A robust fabric often serves as the outer shell, while an inner layer optimised for sliding properties reduces friction in the bearing.

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Advantages

• Suitable for high loads
• Self-lubricating and therefore low-maintenance
• Often more cost-effective than comparable metal bushings in large dimensions
• Corrosion-free