Quote:
Originally Posted by ttldomination
So, suppose a piston uses 1 cubic inch of air, and is fired thirty time. As per your math, it would be:
1 cu in * 30 actuations * (60 output psi / 120 psi) ~> 15 cu inches of "theoretical" storage?
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This is how we calculate air needs, but we usually multiply by 2, which would mean (using the simplified linear model) that you end the match with full working pressure, so that your actuators don't lose force. Basically this also becomes a safety factor - you can continue using the system for more actuations if necessary, but the force will reduce with continued usage.
Quote:
Originally Posted by ttldomination
And as far as the design question is concerned, my question, which I now understand was slightly misleading, was more in regards to CADing the piston.
Are there nice models with the appropriate motion constraints built in, or do people just model in a pole and restrict its range of motion?
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We pretty much exclusively use Bimba cylinders - between the free product voucher in the KoP and the fact that McMaster carries them. Bimba has configurable CAD models of all their cylinders
on their site.
If you use the Direct Insert method (which controls your Solidworks/Inventor/ProE remotely using a Java app and effectively generates the part on the fly) I think it may add the constraints. (It's been a while since I've used it, though, so I may be wrong.)
The Direct Insert process takes quite a while on my computer, so I usually opt for the STEP file download. STEP files don't have constrains, but if I need motion simulation, then I group the parts into either two subassemblies: cylinder and piston, then apply a single constraint to enforce axial motion.
I use Inventor - if you use Solidworks or ProE, it looks like there are application-specific formats which may include constrains.