Air Spring for pick & place
Air Spring for pick & place
(OP)
I would like to use a pnuematic cylinder as an air-spring for pick&place? I need to be able to adjust the pressure from as low as 100 grams, up to 10-20Kg. I am looking at using a double actuated Airpel cylinder which has a graphite piston inside of a quartz tube. These are extremely low friction cylinders. My problem is I'm not sure what I will need on the control end. I need to be able to pick up a part with a lower load (100-500 grams), and place it at a significantly higher load (up to 20Kg). I also need to be able to control the speed for smooth pick/place. Does anyone have an idea of what type of control valves, regulators etc. I would need? I would much appreciate your input!





RE: Air Spring for pick & place
Self relieving regulators could be used in the circuit to limit pressure on one side or the differtial pressure between ports. I have used cylinders in the fashion as counter balances for lifting loads. We also include a air tank near the cylinder to keep the pressure constant.
One other trick I have used for a different reason is to plumb both the ports together on a single rod cylinder. This will make the cylinder extend quickly but be very weak. The amount of force is the area of the rod times pressure. This is mostly done to get a larger cylinder extended quickly in a press application then apply pressure to the rear port only after the ram hits the part. This can save a lot of money on the HPU.
Barry1961
RE: Air Spring for pick & place
RE: Air Spring for pick & place
If this is the case remember that while you can counterbalance the weight that the mass will stay the same and at the speed of most board stuffers decell can be a problem. You could end up with the same effect as a sledge hammer in zero gravity. Making any part you need to acell or decell very low mass.
I would also guess your cylinder stroke will not be much, so venting the air should not be a problem. I would go with plumbing the ports together then switching to rear port to P and front to T(vent). Just calculate your difference between push and pull to see if the force will be right for you with your rod size. I would be afraid to try a self relieving regulator at high speed but I may be very wrong about them.
Big ports, big and short hoses. Maybe a small air tank nearby with 10 times the volume of the cylinder.
Barry1961
RE: Air Spring for pick & place
RE: Air Spring for pick & place
How about a hard stop on your pick stroke? Maybe with a small hyraulic shock to cushion the blow. ACE and Enydine makes little shocks.
Any compliance at the pick point(under tape?) would be a lot less mass to deal with.
It just seems to me that you should be able to stop accurately enough to pick up a part quickly when using a servo system. Maybe your reflected inertia is to high or tuning is off. If you have any integral gain in your tuning I would dump it and try 10:1 P:D ratio. Turn up your proportional until it whines then back it off a bit.
Good luck
Barry1961