Sliding Plain Bearings

In-Depth Analysis of the Advantages and Disadvantages of Engineering Sliding Plain Bearings

1. Definition: Sliding plain bearings are a type of bearing that operates with sliding motion between the bearing surface and the shaft or other moving parts. Unlike rolling bearings, which use rolling elements like balls or rollers, plain bearings rely on a sliding interface.

Sliding plain bearings are among the most fundamental and ancient types of bearings, tracing back to the early stages of human industrial development. A prime example of their historical use includes the ancient Egyptians utilizing sliding methods to move stones for pyramid construction. They employed chutes, hardened slippery slopes as guides, mud-water mixtures for lubrication, and ropes for pulling stones. Interestingly, this basic principle still finds relevance in modern machinery and factory construction.

These bearings are characterized by their large contact surfaces, providing high load capacity. However, this also results in significant resistance. The shift from sliding to rolling bearings marked a pivotal advancement in technology. Rolling bearings, while efficient, require lubrication and protection against dirt and moisture, leading to complex designs with covers and seals. Their cage and ball structures are also prone to external impacts and vibrations, causing noise or potential dislodgement.

Despite these challenges, ball bearings remained a preferred choice until the advent of special material plain bearings. Modern composite self-lubricating plain bearings leverage advanced material technology, blending solid grease, metal matrices, and fiber materials for reliable, lubrication-free operation. Particularly in extreme conditions (such as high heat or humidity), bearings made from high-performance metal composites outperform traditional ball bearings and offer broader application potential.

▲ Comparison of Metal Composite Plain Bearings and Recirculating Ball Bearings

I. Vibration Resistance

Recirculating ball bearings, with their numerous small components, are highly sensitive to shocks, notably during rapid, short-path directional changes. Their assembly requires careful centering with the shaft to avoid steel ball dislodgement or retainer deformation. Metal plain bearings, in contrast, boast simpler construction and lower noise and vibration due to the absence of hardened lubricant material and inter-component collisions.

II. Load Bearing Capacity

Plain bearings’ load capacity hinges on the maximum permissible surface pressure. In contrast to the point contact of recirculating ball bearings, plain bearings have a larger shaft contact area, distributing the load across the sliding element’s entire surface. This allows plain bearings to support considerably higher loads under identical shaft conditions.

III. Shaft Compatibility

Plain bearings create a face contact with the shaft, minimizing shaft erosion. This compatibility extends the shaft’s life, particularly with common materials like lightweight aluminum, carbon fiber, and stainless steel. The optimal material for linear plain bearings varies with the shaft type.

▲ Point Load versus Surface Load

Sliding Plain Bearings Dust and Dirt Resistance

Self-lubricating plastic plain bearings, initially used in the timber and furniture industry, address downtime costs caused by bearing failures. Traditional bearings often fail due to rust, seizure, deformation, or internal buildup of foreign matter like dirt or wood shavings. In contrast, sliding bearings have self-cleaning grooves that expel grit and dust, significantly reducing the impact of contaminants on shaft and bearing longevity.

Applications:

• Food and drug processing
• Home building materials
• Automated warehousing
• Automated cleaning equipment

Experience the benefits of self-lubricating plain bearings now!