View Single Post
  #21   Spotlight this post!  
Unread 12-05-2011, 16:18
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,823
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: Slowing down the action of a cylinder with flow control, mechanical or via softwa

If you're using a double solenoid, then you can just turn it off (rather than reversing it) to stop the additional flow of compressed air before the cylinder reaches the end of it's travel. Probably using an adjustable reed switch feedback (fairly exact final pressure), or less reliably-time, to signal when to stop adding air. That would result in a lower final pressure in the cylinder than the 60-30psi you might be operating from, but it'd start with full pressure to make it move, then have lower than normal pressure by the time it hit the stop.


Quote:
Originally Posted by Randy Forgaard View Post
One odd thing about using the flow control fittings on the cylinders themselves is that it seems like it will reduce the flow of air in both directions --

Cool idea! We could start with a high flow path to raise our arm, and as it reaches the top, we could switch to a low flow path to slow down its motion so it won't slam so hard into the top.
The flow control fittings typically only restrict the air flow in one direction if that's what you are worried about.
For instance, NAS2201F-N01-07S translates to: 1/4" elbow, meter-out, one-touch fitting, NPT, 1/8"port, 1/4" tubing, with seal.
The fittings are marked on the side with a large arrow (no restriction) and a small arrow (restricted flow) showing the direction.
(Added a photo showing the flow arrows)

A side note on the high flow/low flow switching idea.
Just be careful in your design to use only one solenoid value per<R74>.
Quote:

<R74> Each commanded motion of a pneumatic cylinder or rotary actuator must be accomplished via the flow of compressed air through only one approved pneumatic valve. Plumbing the outputs from multiple valves together into the same input on a pneumatic cylinder is prohibited.
Restricting the flow from the exhaust port of a single valve would affect both extension and retraction of the same cylinder if the valve is connected to both ends.
Attached Thumbnails
Click image for larger version

Name:	FlowControl.jpg
Views:	17
Size:	128.1 KB
ID:	10692  
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle

Last edited by Mark McLeod : 12-05-2011 at 18:27. Reason: Added photo