Pneumatics help please

Sorry to be a bother but could use a little help. I’m not a pneumatics guy. I’m actually a RN. I just have a little side thing packaging parts. I need two small pneumatic pistons to work, #1 first then # 2 emmediatly after or as first one is retracting. Engaging cycle with one step on pedal. Any help would be appreciated.

Let’s see if I understand the question:
You have 2x pneumatic cylinders and 1x pedal. You want to fire the cylinders #1 extend, #1 retract and as #1 retracts #2 extends (and after some time #2 retracts).

There’s a few ways to do that.

One possible way–if I knew where to find the parts–would be to set up the pneumatic circuit itself to trigger the second unit. There’s also the option of using a microcontroller to trigger solenoids with timing controlled by same. There’s always having two separate pedals but that’s likely to be rather cumbersome.

What if anything do you already have for electric controls in this setup?

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Not very familiar with microcontroller. You very correct on process. Would i need 2 solenoids working off controller? If I get this right I would double my production. Which means I double my income. Wod be nice.

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You’d probably need two solenoids, yes. There might be a way to do it entirely pneumatically, though.

See, I know there are switches around that can toggle airflow and make a logic circuit (sort of “if this is here then activate this valve”). Depending what you’re doing you might not even need the pedal.

So… here’s my thoughts.

  1. You’re going to need a control valve. There are foot-pedal control valves, so let’s keep things simple and use one of those.
  2. Some of the foot-pedal valves come in 2-action types (so one per foot or rapid-fire with one foot). That might be making it too much work for you, though. We’ll file that away for later.
  3. I’d suggest using the exhaust air from the first cylinder’s retraction to extend the second cylinder, but that simply won’t work for a variety of reasons.
  4. On the other hand… a well-placed check valve will probably do exactly what you want it to do.
  5. You haven’t said when you want the #2 cylinder to retract…

I’ll do some quick diagramming and see if what I’m thinking is going to work.

2nd cylinder needs to retract right after the extend. …I have a nail and plastic piece go in jig. #1 cylinder pushes nail in plastic piece and retracts. #2 cylinder pushes the plastic part out of jig, down and into box. Has to be done with one step on pedal for efficacy. 2 pedal system becomes to cumbersome and I lose time.

Immediate retract, eh?

That’s going to cause some interesting nuisance without a microcontroller. I’m trying to see what if anything might work to automatically bring it back and I’m coming up empty. (There’s a fair amount of ideas involving switches but I’d have to get exceptionally creative to get something that would work–and they all involve a spring-return cylinder). I’m out of my depth on this one.

If you have a microcontroller, it’s simple enough. Pedal switch (or button, or…) triggers a command that says fire 1, wait 1 second, release 1 and fire 2, wait .5 seconds and release 2. You’ll need a microcontroller and a pair of pneumatic solenoid valves. Arduinos are simple; this would be an Arduino Micro job I think as you only need 1 input and 2 outputs.

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It seems like there are two actions here: Pushing the nail into the piece then ejecting it.

Is it possible that we could use one pneumatic cylinder and make it do both?
Extend → Push in nail
Retract → Eject piece

Going to throw that out there. Will respond back once my subconscious gets to process it more.

I was thinking about that. It would depend a lot on jig design, but you could rig a linkage to do that.

OK, so this is going to sound a little radical. If you want this to be a fully automated process, where all you do is apply air pressure and the mechanism operates from there, you may want to look at a having the cylinder rod motion open and close the pneumatic valves. Steam locomotives used something called a Stephenson Valve Gear or a Walschaert Valve that runs on an eccentric cam on the axle to push the steam valves open and closed at the right time to apply the steam pressure on the correct side of the working pistons. You could do something similar for your setup (except using a linear valve actuator instead of a rotating valve actuator). When the cylinder rod reaches the end of the travel to drive the nail, a linkage also attached to the same rod could manually open a valve to apply pressure in the opposite side of the cylinder to cause it to retract. Then, during the retraction of the #1 cylinder rod, it could pass by and flip a toggle valve that would route pressure to cylinder #2 causing it to extend. You could have similar linkages on cylinder #2 that would open and close the valves to apply pressure to retract cylinder #2 and extend cylinder #1 for the next cycle.

A similar approach would be to have the cylinder rods open and close contact switches at some point in their travel and then you could have those switches apply power to your solenoid valves. You could use limit switches or toggle switches and have some physical feature attached to the mechanism on the ends of the rods actuate those switches as you pass by them.


Another thing you might consider doing is asking us a different question. There seems to be two problems currently. let’s call them X and Y

X = How do I use actuate two pneumatics
Y = How do create an automated system to put a nail into a piece, then eject it into a bucket.

If you specify the parameters (cost, resources, jig type, etc) of Y well enough, we might be able to help you find plenty of additional solutions.

It would be very helpful if the amount of motion required is defined (in inches or mm). Otherwise, If the control of the solenoids is purely based on time, variations in the plastic pieces may cause incomplete penetration.

I’m looking into microcontroller. Suggestions on one. Not looking to get to crazy. Remember I do this on the side for couple bucks in my garage.

Arduino Uno.

Cheap, easy to program with a computer, lots of training material out there and possibly even some example code. Able to drive a solenoid valve.

Nice. Thanks for the time. Ill look into those controllers and see what we come up with.

Personally, I prefer the Arduino pro micro. Most of the pins, much smaller, and you only need a USB micro cable [and your PC] to program it. I’ve built it into T-shirt launchers, flag-waving hats, and more.

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