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General Category => Do-more CPUs and Do-more Designer Software => Topic started by: timk5000 on August 16, 2017, 10:48:36 AM

Title: A good way to control a pneumatic cylinder
Post by: timk5000 on August 16, 2017, 10:48:36 AM

I have tried several different ideas for controlling  a double acting air cylinder. I am sure there is a proper way to do it but have not really found it.

Does anyone have examples of controlling air cylinders they could share or point me to some examples.

Thanks

Title: Re: A good way to control a pneumatic cylinder
Post by: DLTimmons on August 16, 2017, 11:30:36 AM

What do you mean by controlling air cylinders? If you trying to position mid stroke with it then for get it. If end of stroke to end of stroke simple air valves.

Title: Re: A good way to control a pneumatic cylinder
Post by: deep6ixed on August 16, 2017, 01:27:29 PM

We have quite a bit of pneumatics at our shop, what exactly are you trying to do?

Title: Re: A good way to control a pneumatic cylinder
Post by: timk5000 on August 16, 2017, 01:54:19 PM

All I need is an example of ladder program showing how to do the following

I have a double acting cylinder with a sensor for extended and another for retracted
I have a air valve with 2 coils that will extend and retract the cylinder.

As a starting point for a project I want to make sure the cylinder is retracted.
I usually start with a latch circuit to start "Home Mode"

Then if the retracted sensor is not made I want to turn on the output to retract the cylinder until it is retracted and then turn off.

Usually when I try this I have to use a timer or it will just cycle real fast and never stop.

I was hoping someone new of a site that had several examples of controlling cylinders for different circumstances.

Thanks

 

Title: Re: A good way to control a pneumatic cylinder
Post by: Controls Guy on August 16, 2017, 02:29:25 PM

You might have the wrong type valve to be able to turn it off when it gets to the end of travel.  Some valves have detents on the spool so it stays at the last position you signaled, but some have a third position in the center and automatically return to it if neither coil is energized.  Then the three-position ones come in several flavors.  Both ports closed, both exhausted, both pressurized, etc.

Also, I include a jam/sensor fault timer if the valve is energized and doesn't make it to the sensor within a reasonable time, as well as sensor diagnostics (for example, both end sensors should never be able to come on at the same time, so if they do, that's also a fault.  The jam fault timer will catch sensors that don't come on when they should.  And....if you do a jam fault, you should also monitor supply air pressure, and create a fault for that, and interlock that fault to prevent a jam fault, otherwise you'll be getting jam faults when the problem is actually lack of air.

Title: Re: A good way to control a pneumatic cylinder
Post by: ATU on August 16, 2017, 05:57:24 PM

Try stage programing. Its a piece of cake for sequential stuff like that.

Title: Re: A good way to control a pneumatic cylinder
Post by: AustinT on August 16, 2017, 11:54:58 PM

I have used s2 valves from enfield technologies with success .  You will need feedback and an analog signal for control

Title: Re: A good way to control a pneumatic cylinder
Post by: Evilbeard on August 17, 2017, 09:05:00 AM

This would look at the cylinder, retract if it wasn't, and then go to a stage where it was waiting on an input to "fire" the cylinder. It would then extend the cylinder, and then retract again, and wait for the process to repeat.

(https://i.imgur.com/xDYV2Wu.png)