Assembly of Rolling and Plain Bearings

Assembly of Sliding Bearings

Sliding bearings operate on sliding friction, offering smooth performance, low noise, and the ability to withstand heavy and impact loads. They are categorized into integral, split, and tile types based on their structure.

1. Assembly of Integral Sliding Bearings (Bushings)

• Method:
  • Primarily assembled using pressure and hammering methods.
  • Hot installation is used for special cases.
• Material:
  • Most bushings are made of copper or cast iron.
• Precautions:
  • Use a wooden hammer or hammer pad to prevent tilting.
  • Ensure oil grooves and oil holes are correctly positioned after assembly.
• Post-Assembly Adjustments:
  • If deformed, trimming is required:
    • Smaller sizes: Ream.
    • Larger sizes: Scrape.
  • Maintain clearance tolerances to prevent sleeve rotation.
• Positioning:
  • Use positioning pins or seam screws to ensure proper contact between the sleeve and housing.
• Drilling:
  • Use a punch to guide the drill or a short drill bit for accuracy.

2. Assembly of Split Bearings

• Structure:
  • Consist of two shingles on the shaft tile and a shim at the joint to set clearance.
• Steps:
  • Assembly of Shaft Tile and Bearing Body:
    • Ensure the upper and lower shaft tiles fit well with the bearing body.
    • Use thick-walled tiles as benchmarks for scraping if necessary.
    • For thin-walled tiles, ensure the parting surface is ~0.1 mm higher than the bearing body.
  • Installation of Shaft Tile:
    • Prevent radial or axial displacement.
    • Use shaft tile steps or pins for positioning.
  • Shaft Tile Scraping:
    • Start with the lower shaft tile using its matching shaft research point.
    • Adjust by increasing shim thickness as scraping proceeds.
    • Tighten the bearing cover to ensure the shaft rotates freely with minimal clearance.
  • Measurement of Bearing Clearance:
    • Use the lead pressure method:
      • Place lead wires (larger than the bearing clearance) on the journal.
      • Tighten the bearing cover and measure the flattened lead wires for average thickness.
    • Clearance should be 1.5‰–2.5‰ of the shaft diameter (e.g., 0.09–0.15 mm for a 60 mm shaft).

Rolling Bearing Assembly

Rolling bearings are favored for their low friction, compact size, and easy maintenance.

1. Technical Requirements for Assembly

• The coded end face of the bearing must face outward for visibility.
• The radius of the journal or shell hole step must be smaller than that of the bearing.
• Ensure no skewing after assembly on the shaft or in the shell hole.
• At least one of two coaxial bearings must accommodate shaft movement due to thermal expansion.
• Prevent dirt from entering the bearings during assembly.
• Ensure the assembled bearings operate flexibly, produce minimal noise, and maintain temperatures below 65°C.

2. Assembly Methods

• Hammering Method:
  • Use a hammer pad against a copper rod to avoid direct hits on the bearing rings.
• Press Assembly:
  • Use a screw press or hydraulic press for bearings with large interference.
  • Ensure the shaft and bearing are leveled and lubricated before pressing.
• Heat Assembly Method:
  • Heat the bearing in oil to 80°C–100°C to expand the bore for installation.
  • Not suitable for bearings with dust covers or pre-filled grease.

3. Tapered Roller Bearing Clearance Adjustment

• Adjust clearance post-assembly using shims, screws, or nuts.

4. Assembly of Thrust Ball Bearings

• Identify the tight ring (smaller diameter) and loose ring.
• Ensure the tight ring remains static relative to the shaft steps or hole end face during operation.

Key Takeaways

• Sliding bearings are ideal for heavy loads and low-noise applications.
• Rolling bearings offer low friction and compact design.
• Proper assembly techniques and clearance adjustments are critical for optimal performance.
• Use appropriate lubrication and positioning methods to ensure longevity and efficiency.

Bimetallic Plain Bearings Overview

Bimetallic plain bearings are engineered to deliver high strength, excellent bearing capacity, and superior wear resistance. They are constructed using a high-quality low carbon steel substrate with a sintered tin bronze alloy surface, making them ideal for applications involving medium loads, low speeds, and high-impact loads.

Manufacturing Process

1. Material Composition:
   • Substrate: Low carbon steel for structural strength.
   • Surface Layer: Sintered tin bronze alloy for wear resistance and lubrication properties.
2. Production Process:
   • Multiple high-temperature sintering and densification steps ensure a reliable bimetallic strip coil.
3. Customization:
   • Oil grooves, oil holes, and specific features can be incorporated into the friction surface to accommodate various lubrication conditions.

Key Features

• High Strength: Capable of withstanding high-impact loads.
• Excellent Bearing Capacity: Suitable for medium to heavy loads.
• Wear Resistance: Enhanced durability due to the tin bronze alloy surface.
• Compact and Lightweight: Facilitates mass production and conserves copper.
• Temperature Resistance: Performs well under high-temperature conditions.

Advantages Over Solid Bearing Materials

• Mass Production: Easier to manufacture in large quantities.
• Compact Design: Reduces size and weight of the bearing.
• Copper Conservation: Uses less copper compared to solid bronze bearings.
• Superior Performance: Better bearing capacity and temperature resistance.

Applications

Bimetallic plain bearings are widely used in various industries and applications, including:

Automotive

• Engines: Connecting rod sleeves, rocker arm shafts, crankshaft thrust discs.
• Chassis Systems: Spring shafts, bushings, brake shoe sleeves.
• Transmission: Variable gear sleeves, friction plate clutch sleeves.

Industrial Machinery

• Gear Pumps: Side plates and bushings.
• Lifting Equipment: Bearings for heavy-duty applications.

Other Fields

• Engineering, Metallurgy, Mining, and Petroleum: High-load and high-impact applications.
• Textiles and Agricultural Machinery: Wear-resistant components.
• Machine Tools and Hydraulics: Precision bearings for smooth operation.
• Locomotives and Transportation: Durable bearings for heavy loads.
• Instrumentation, Household Appliances, and Office Equipment: Compact and lightweight solutions.

Summary

Bimetallic plain bearings are a versatile and reliable solution for applications requiring high strength, wear resistance, and excellent bearing capacity. Their specialized manufacturing process allows for customization to meet specific lubrication and operational needs, making them a preferred choice across automotive, industrial, and general machinery sectors. Their compact design, lightweight nature, and superior performance further enhance their appeal in modern engineering applications.

Comparison of Rolling Bearings and Plain Bearings

Bearings are critical components in mechanical systems, supporting rotating shafts and reducing friction. They are broadly classified into rolling bearings (rolling friction) and plain bearings (sliding friction). Here’s a detailed comparison of the two:

1. Structure and Motion

• Rolling Bearings:
  • Contain rolling elements (balls, cylindrical, tapered, or needle rollers).
  • Support the rotating shaft at point contacts, increasing with the number of rolling bodies.
  • Motion type: Rolling.
• Plain Bearings:
  • Lack rolling elements; rely on a smooth surface for support.
  • Motion type: Sliding.
  • Contact type: Surface contact.

2. Bearing Capacity

• Rolling Bearings:
  • Lower load capacity compared to plain bearings.
  • Less capable of withstanding impact loads.
  • Capacity decreases with higher speeds due to centrifugal forces.
• Plain Bearings:
  • Higher load capacity due to larger contact area.
  • Fully liquid-lubricated bearings can absorb vibrations and handle significant impacts.
  • Capacity increases with higher speeds due to dynamic pressure.

3. Friction Coefficients

• Rolling Bearings:
  • Lower and more stable friction coefficient under standard conditions.
• Plain Bearings:
  • Friction coefficient varies greatly due to external factors like speed and vibration.
  • Higher starting friction due to the absence of a stable oil film (except in hydrostatic bearings).

4. Speed Applicability

• Rolling Bearings:
  • Limited to medium and low speeds due to centrifugal forces and temperature constraints.
• Plain Bearings:
  • Perform well at high speeds, especially fully liquid-lubricated bearings.
  • Hydrostatic sliding bearings can reach up to 100,000 r/min.

5. Power Loss

• Rolling Bearings:
  • Lower power loss due to small friction coefficient.
  • Loss increases with improper lubrication or installation.
• Plain Bearings:
  • Fully liquid-lubricated bearings have low friction power loss.
  • Hydrostatic sliding bearings may experience higher overall losses due to oil pump demands.

6. Service Life

• Rolling Bearings:
  • Design life of 5 to 10 years, often requiring replacement during overhauls.
• Plain Bearings:
  • Incomplete liquid lubrication bearings require regular replacement due to wear.
  • Fully liquid-lubricated bearings can theoretically last indefinitely, though dynamic pressure bearings may suffer fatigue damage over time.

7. Rotational Accuracy

• Rolling Bearings:
  • Higher rotational accuracy due to minimal radial clearance.
• Plain Bearings:
  • Incomplete liquid lubrication bearings may experience instability and wear, reducing precision.
  • Fully liquid-lubricated bearings benefit from oil films that enhance accuracy.
  • Hydrostatic plain bearings offer even greater precision.

8. Other Considerations

• Rolling Bearings:
  • Use minimal oil, grease, or solid lubricants.
  • Require cleanliness and sealing.
  • Easy to replace without journal repairs.
• Plain Bearings:
  • Use larger volumes of liquid or gas lubricants.
  • Require higher cleanliness standards.
  • More frequent replacement and sometimes journal repairs are needed.

Summary of Key Differences

Applications

• Rolling Bearings:
  • Automotive wheels, electric motors, gearboxes, and machinery requiring high precision.
• Plain Bearings:
  • Heavy machinery, marine applications, high-speed turbines, and environments requiring high load capacity.

Both types of bearings have their unique advantages and are chosen based on specific application requirements such as load, speed, precision, and operating conditions.