Friction in pneumatic cylinder

[PrintScaffold]

Hello everyone!

Pneumatics and sealings is not exactly my field, hence the question.
Is there a rule of thumb helping to estimate losses in the pneumatic cylinder? Pristine Force calculation is obviously Area times Pressure. Is it possible to estimate the reduction of the force due to friction in the cylinder of fairly common design (no quirks)?

http://www.cadroad.com

 

[EdStainless]

When the cylinder is in motion the friction is negligible.
However the initial breakaway force (sticktion) can be an issue.
Look in the design guides from some of the cylinder makers (SMC or Bimba).

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P.E. Metallurgy, Plymouth Tube

 

[btrueblood]

Rolling diaphragm cylinders can have much lower friction/stiction than more traditional o-ring or wiper seal designs.

Airpot is a brand of "cylinders" that have ridiculously low friction (tightly toleranced graphite pistons sliding in glass tubes) but at the expense of a slight leakage past the piston.

The biggest loss in pneumatics is expansion or throttling loss, i.e. they are never controlled well enough to make best use of the available work of the expanding gas.

 

[EdStainless]

Just like liquid cylinders air cylinders only work when there is actually a small amount of leakage. When there is no motion the leakage is very small.
People usually only care about it when they are working from a limited gas source (small bottle) and then they use special tricks.

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P.E. Metallurgy, Plymouth Tube