SKF
Friction (Bushings)
Friction characteristics of SKF plain bushings depend on the material pair, surface roughness, load, and speed. PTFE-based composites exhibit low, consistent friction coefficients (0.03–0.08) making them ideal for stick-slip sensitive applications. POM materials have slightly higher friction but better wear resistance under high loads. SKF provides friction coefficient data for both dry and initially greased conditions. Understanding friction helps designers calculate actuator force requirements and predict start-up torque in linkage and pivot applications.
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PTFE Composite µ
0.03‑0.08; near‑constant across speed range.
POM Composite µ
0.05‑0.12; slightly higher but more load‑resistant.
Bronze (lubricated) µ
0.06‑0.10 with grease; 0.15‑0.25 if dry.
Breakaway vs. Running
PTFE composites show very low breakaway, ideal for precise low‑speed movements.
Friction‑Force Calculation
Enables actuator sizing and power loss estimation.
Temperature Influence
PTFE friction drops with increasing temperature; POM remains stable.
Why Low Friction Matters in Pneumatic Cylinder Pivots
A pneumatic cylinder has limited force. Excessive bushing friction can cause the cylinder to stall or require a larger, more expensive bore. PTFE composite bushings minimise this friction, allowing designers to use smaller, more efficient cylinders, reducing air consumption and cost.
Testing Friction in the Field
A simple pull‑test with a spring balance attached to the pivoting part indicates whether the friction is normal. If the force exceeds twice the calculated value, the bushing may be overloaded, misaligned, or contaminated. This quick check helps maintenance teams identify bushing problems before they cause linkage damage.