Pneumatics firing at different times?

My team and I have been having a hard time understanding this issue, we are all new to pneumatics and have not been able to understand the problem.

Pictured above is a photo of our grabber and a link to the cylinders used, it features a 775 in the center and two pneumatic pistons to actuate the two arms which have spinning wheels at the ends. When we trigger the 5-way solenoid, there is a large delay between when the click occurs and when the cylinders move. This is something I have not seen other teams have an issue with even with similar styles of grabber. Another interesting thing which happens is that one cylinder swings its arm slightly faster than the other which leads me to believe that they are not being pressurized fast enough. We have checked the pressure, which is 120psi stored and 60psi working, the solenoid is very close to the cylinders maybe 7-8 inches away while I estimate the tank has around 100 inches of tube. There also don’t seem to be any leaks in the system, the compressor fires at the start then stops at 120psi. After the pistons and arms actuate, the arms are extremely hard to move in both directions. The pistons, as shown in the photo, are also placed far away from the pivots to give them a larger advantage but still the system is slow.

Would a bad solenoid or improperly wrapped fitting cause an issue like this, or could the system be too long?

Any help would be appreciated,


What solenoid valve are you using?

We are using this solenoid, it looks like its well within spec, I think it has a 1/8 inch valve.

I would check out the supply line. It looks like you have it running up the arm. I would make sure you don’t have it kinked somewhere or maybe a zip tie was pulled too tight. If you have more air line just temp it in from the source to the valve without running through the arm. If that makes it better then you know something is wrong where it goes up the arm.

A picture of the valve could help as well. Typically a valve like that would have the 2 outputs that I can see in the picture. Also has 3 ports on the other side. The middle most likely is the pressure port and the other two would be exhaust. Sometimes the exhaust have mufflers in them. In industry I have seen dirty mufflers that will make cylinders run slow.

From what I remember, the air is going into the middle of the three ports, and the other two ports are shut with brass plugs, is it normal to have these two ports closed?

I bet that’s your problem. Remove the plugs and try it

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There should be 5 ports, 3 on one side and 2 on the other. The middle on one side is the “supply” port, and is where the supply side of your pneumatics system gets plumbed. The other 2 on that side are exhaust ports and should generally be left open (though there are reasons you may want to plug one or both in more advanced usages). The other 2 ports are working ports and will generally be connected to either end of your pneumatic cylinder/“piston”. The valve will toggle between which port gets supply pressure, and which is connected to its associated exhaust port.

This image shows a single solenoid, whereas yours is a double, but this still gets the idea across fairly well.


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Definitely a problem. Those are the exhaust ports. When you switch direction, the air flows out of the (previously) pressurized side through those ports. Slowing that down (or stopping it altogether) will make the piston move slower (or possibly not at all).

If you need still need help, find me on Friday when pits open - I’ll be your LRI at North Star!

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Thank you all so much for the help, I definitely learned a lot about pneumatics and will share this information with my team.

I will also try to post a quick clip tomorrow of the before and after for future reference, thanks again!

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