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Unread 03-02-2011, 12:59
cmass cmass is offline
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Re: Pistons only halfway up

Quote:
Originally Posted by tonystark_23 View Post
Hi, I am not an expert on the situation, but i have mentored a team that did multi position pneumatic cylinders. (pistons). Bimba sells pistons with magnetic switches attached to the outside. The way this works is that the "plunger" in the cylinder has a magnetic tip. The magnetic switches on the outside of the cylinder detect when the plunger passes and return a value 0 or 1. You can use this value to write code that turns on the solenoid and then turns it off when it reaches the appropriate switch position.
The purpose of the magnetic switches on cylinders is to confirm that the piston has reached its destination (start and or finish). The reason that the switch can be placed anywhere along the travel is because people often design systems where the cylinder never reaches full stroke.

You should NEVER plan to try to stop a pneumatic cylinder partially through its stroke to a defined position with the use of air pressure / flow. There are precision valves which can accomplish this but there is no reason to do it that way. Hydraulic cylinders and valves do this all the time but oil is not as compressible as air!

As others have mentioned, use two position cylinders, mount cylinders in series (we are doing this), put intermediate hard stops or use motors and chain or belt.