What Is an Oilless Bushing?
An oilless bushing, also known as an oil-free bushing or bearing, is a type of plain bearing designed to function without the need for lubrication. Unlike traditional bearings that require oil or grease for smooth operation, oilless bushings contain materials with inherent lubrication properties, enabling them to support rotating shafts in industrial machines efficiently.
Applications of Oilless Bushings
Oilless bushings are essential in various applications where lubrication is impractical or undesirable, including:
- Food processing machinery, where they avoid contamination.
- Industrial machinery where lubrication access is difficult.
- Automobiles, railcars, construction equipment, printing machinery, housing equipment, and power plants for their lubrication-free operation.
They offer significant benefits such as reduced maintenance costs and simplified machinery design by eliminating the need for lubrication systems.
Working Principle of Oilless Bushings
Oilless bushings achieve lubrication-free operation through:
1. Solid Lubricants
Incorporating solid lubricants like molybdenum disulfide or metallic saponite into the bushing material, reducing friction.
2. Engineering Plastics
Using engineering plastics with low friction coefficients, such as Teflon (PTFE), polyacetal, and PEEK, which offer excellent balance in strength and safety.
Types of Oilless Bushings
Oilless bushings are categorized by their material composition into:
1. Resin Type
Made from materials like polyacetal and tetrafluoroethylene, these bushings are lightweight, low-cost, and have a low coefficient of friction.
2. Double-Layer Type
These bushings feature a back metal and a surface layer of resin or solid lubricant, offering a compact design and excellent mechanical strength.
3. Metal Type
Constructed from copper or aluminum alloys embedded with solid lubricants like graphite, suitable for high-load applications and offering a long life.
Maintenance and Lifespan of Oilless Bushings
The lifespan of an oilless bushing is determined by wear and tear from use. Theoretical formulas calculate the wear rate, considering factors like specific wear rate, design surface pressure, operating speed, and friction time. Proper design ensures that the bushing meets its required lifespan without exceeding the designed wear volume, thereby maintaining operational efficiency and reliability.