Technical Analysis of Sliding vs. Rolling Bearings: Selection Guide & Application Comparison

May 8, 2025

I. Core Definitions & Fundamental Structures

1. Rolling Bearings

Rolling bearings facilitate relative motion between shafts and bearing housings via rolling friction. Their core structure includes:

Inner Ring: Tightly fitted to the shaft, rotating synchronously with it.
Outer Ring: Fixed in the housing, providing foundational support.
Rolling Elements: Balls, rollers, or tapered rollers that convert sliding friction into rolling friction (key performance determinants).
Cage: Distributes rolling elements evenly, preventing collisions and guiding their trajectory.

Friction characteristics depend on manufacturing precision (e.g., raceway roundness error ≤1μm). Suitable for medium-to-high speeds (≤10,000RPM), typical in motors and gearboxes.

2. Sliding Bearings

Sliding bearings carry loads through surface-contact sliding friction between the shaft and bearing bushing, with core advantages in material adaptability:

Metallic Types: Tin-based Babbitt alloy (low melting point, self-lubricating) and copper-based alloys (high thermal conductivity).
Non-Metallic Types: Engineering plastics (e.g., PA66+GF30, wear-resistant and lubrication-free) and carbon graphite (heat-resistant up to 200℃+).

Friction and wear are reduced via lubricating oil films (5–50μm thickness) or self-lubricating materials. Ideal for low-speed heavy-load or high-precision scenarios, such as steam turbines and injection molding machine clamping mechanisms.

II. Core Performance Comparison Matrix

Comparison Dimension	Rolling Bearings	Sliding Bearings
Friction Type	Point/line-contact rolling friction (μ=0.001–0.005)	Surface-contact sliding friction (boundary lubrication μ=0.1–0.3; full-fluid lubrication μ=0.001–0.01)
Structural Complexity	Four-component precision fit (clearance control ≤10μm)	Simple bushing structure (reliant on material properties and surface treatment)
Speed Range	Medium-to-high speed (≤10,000RPM, limited by rolling element centrifugal force)	Wide speed range (hydrostatic bearings up to 100,000RPM, dependent on lubrication state)
Load Characteristics	Point loads (suitable for combined radial/axial loads)	Uniform surface loads (high heavy-load capacity, single-bearing load ≥10,000N/mm)
Precision Grade	Rotational accuracy ±5μm (ABEC-7 grade)	Dynamic accuracy ±2μm (hydrostatic bearings)
Maintenance Requirements	Periodic lubrication (grease lubrication cycle 500–1000 hours)	Strict lubrication management (oil cleanliness ISO 16/14 class)
Noise Level	Mid-high frequency noise (60–85dB, prominent at high speeds)	Low-frequency noise (≤55dB, no rolling element impact)

III. In-Depth Performance Analysis

1. Friction Characteristics & Power Loss

Rolling Bearings:
Low starting friction resistance (≈0.1% of rated load), but windage loss from cages increases at high speeds. Ideal for efficiency-critical applications (e.g., power tools).
Sliding Bearings:
Require overcoming boundary lubrication resistance at startup (≈1–3% of rated load), but power loss is 30% lower than rolling bearings under full-fluid lubrication. Suitable for continuous-operation equipment (e.g., industrial fans).

2. Lifespan & Failure Modes

Rolling Bearings:
Typical L10 lifespan of 5–10 years, with primary failure from rolling element fatigue pitting (correlated with load spectrum, safety factor ≥1.2 required).
Sliding Bearings:
Theoretically infinite lifespan (no fatigue failure), but bushing wear rate must be controlled ≤5μm per 1,000 hours. Ideal for long-cycle equipment (e.g., marine propeller shafts).

3. Environmental Adaptability

Rolling Bearings:
Require dust-proof sealing (IP65+). Lithium-based grease is necessary for low-temperature scenarios (-40℃~+120℃).
Sliding Bearings:
Self-lubricating plastic types operate oil-free. Metallic types adapt to high humidity (RH≥90%) via surface coatings (e.g., molybdenum disulfide).

This technical translation maintains professional terminology and structural consistency with the original, ensuring accuracy in engineering parameters and application contexts.

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