Friction in linear guides.

2024-06-17

One big reason to minimize friction? It extends the lifespan of your linear guide. Why?

• Less friction = less heat
• Less heat = less thermal expansion = less stress
• Less heat = better lubrication retention
• And of course, less wear on surfaces

What affects friction in a linear guide? A few key factors:

• Type of guide: Sliding guides = high friction. Linear guides = rolling motion = much lower friction.
• Contact surface design: A ball rolling on a shaft moves uniformly. But in a linear guide, ball contacts have varying surface speeds, leading to slightly more friction – but much higher load capacity.
• Rollers are best in terms of low friction and high load.
• Lubrication: Proper grease or oil keeps balls from contacting the raceway directly – they "hydroplane" on a thin film.
  - The important factor is the base oil viscosity, not just whether it's grease or oil.
  - Grease is basically oil mixed with soap to make it thicker.

Why do we want minimal friction?

• Save energy
• Reduce environmental impact
• Ensure smooth operation

Example:

If your load weighs 1000 kg (approx. 10,000 N), and your linear guide has a friction coefficient of 0.002, the force required to move it is:
FR = µ × FN = 0.002 × 10,000 = 20 N
So you only need 20 N to move 1 ton!

Note: seals also add some friction, but they don't reduce the guide’s lifespan.

Check out the video with Carry Lindholm on this topic: