Pneumatic Construction Practice

FIRST General Forum
1

Hello,

I want my team to get practice building, programming, and operating a pneumatic arm with a gripping mechanism. Currently, they do not have that experience or skills. Can someone send me a list of materials and some build/programming guides?

2

Spectrum Robotics has a great deal of information on all topics. Below is their Advanced Pneumatics guide.

WPI.lib on wiring
For software there are many topics in WPIlib
FIRST Pneumatics Manual

3

Others likely to give you a good list of basics, but if learning is the goal here there are a few things that will really help with trouble shooting and such:

  • Cutter to get 90deg angles on tubing
  • Teflon tape
  • Spray bottle with soapy water to find leaks
  • flow valves
  • Don’t forget various mounting hardware including rod ends and brackets (Should be cheaper plastic ones around)

Some projects:

  • A good first project is a simple pneumatic gripper for an inner tube, 1" *1/8" aluminum bar and hardware store hinges makes an easy set of hardware to play with for this task.

  • A more advanced project is mounting and controlling the ratchet on a winch with a small cylinder.

  • Coupling two cylinders end to end to get 3+ position control with two cylinders. Remember, pneumatics are not hydraulics, this catches some novices up every once and a while and there are multiple threads on this forum about that.

Other:

Here is some basic freeware cad software I use for designing linkages. It takes a little bit to get used to it, but is a valuable tool to check motion paths etc. Also useful for motor control. Good software for teaching linkages because it doesn’t have assemblies and such that one would have to learn in a full featured CAD software to get basic geometry. It has some preloaded examples to let you see what is possible.

4

I’d split into 3 main concerns.

First just knowing how pneumatics work and the rules. The game manual is a good source of info for that and also there are different guides. Spectrum 3847 has one. They also have an advanced guide that has some interesting info.

You’ll find that there are many different options for pneumatics and purchasing the correct parts is part of the challenge. It is okay to use the regular gauges and regulators, but many have switched to the automation direct mini ones to save weight and space.

Here is the slides from spectrum training:

Second, is how to design pneumatic cylinder joints. There is some CAD training people have done but I don’t have one to share.

Third, is programming. I think the best source is is docs.wpilib.org and search pneumatics. If you want more, find robots that use pneumatics and lookup any public code for it on GitHub. Our claw and elevator were pneumatic this year: GitHub - frc1108/Robot2023

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5

Thank you so very much. It looks helpful.

6

Thank you. Good stuff.

7

Thank you. Good info.

8

Also we have a pneumatics section on frczero.org that is mostly filled in. It references WPIlib but focuses on the hardware components and some basic troubleshooting. We are missing some component images still. Our cataloging got interrupted with moving labs over the summer.

Edit: Also the Official 2024 safety manual talks about Pneumatics safety a tiny bit.

Pneumatic Energy (FIRST Robotics Competition Only): • Always vent any compressed air to the atmosphere (this applies to all parts of the pneumatic system). • Open the main vent valve and verify that all pressure gauges on the robot indicate zero pressure.

But that’s all it has to say on the subject.

1 Like
9

Would anyone out there who regularly does this share their best practices or even a video of the process? We struggled to find some mysterious leaks last year, but never quite had the nerve to start spraying water into our robot

10

Great. Thanks.

11

That’s a valid concern. The general idea is isolate to some area of the robot, test connections in a methodological order. It is almost always a bad connection into a push fitting that causes problems, either a bad cut end or strain on the fitting.

Basic order of operations:

  1. Determine if the leak is upstream or downstream of your high pressure side. (Remember you can always use a “T” with a short piece of line in two ends as a makeshift stopper to help isolate), mark any fittings you have tested with masking tape or some other tracking to avoid doing extra/redundant work.
  2. Look for any lines that are putting leverage or strain on a push fitting, if you find any you need to re-route the tubing or use a more appropriate fitting. This can also occur if lines are just a tiny bit too short.
  3. Check connections to/and air tank integrity, plastic can crack! (you can use soapy water here to help)
  4. Check for Teflon tape on NPT connections (again, careful application of soapy water)
  5. Continue working your way down on the low pressure side, remembering that some lines will not be pressurized on double acting cylinders.
  6. Test the other side of double acting cylinder line.
  7. Test any other connections you may have unplugged with a spray bottle of soapy water (1-2 Tbs of soap per quart). Use a paper towel to prevent over spray, you do not need much, just get the connection wet, not dripping. if there is a leak you should see bubbles. Another option is to apply soapy water with a damp sponge.
  8. Test other joints, if you found one leak there may be others. It may be easier to start with areas that do not have any electronics/motors nearby. (REMEMBER check the other side of double acting solenoids)
  9. Whenever you find a connection that looks suspect be sure that the tubing has a nice clean 90 degree cut with no burrs. (this can easily occur if you use scissors or a bandsaw to cut the tubing)
  10. Other sources of leaks: solenoid gaskets, damaged fittings, over tightened metal fittings (no one wants a cracked compressor head), defective pressure regulator (yet to see this in the wild), overly used and abused push fittings (the seals don’t last forever), not clean cut line ends, not clean cut line ends, not clean cut line ends.
12

We often use a cup of soapy water and a paper towel from the restroom to dab the soapy water onto the joints. We often don’t have a spray bottle handy and we find that this works just as well.

If there are electrical components that may get wet, cover them with something like a piece of cardboard. There is no need to use a lot of the water.

1 Like
13

If you are not in love with the idea of putting soapy water on your robot, an alternative is to buy a stethoscope, remove the part that normally goes on your chest, and just hold the open tube end next to any pneumatic fitting. You’ll be able to hear the air leaking, loud and clear.

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14

I bought a stethoscope to diagnose a vacuum leak in my car after seeing a student with one set up the way you describe at Ontario Provincial Champs. I have loaned it to my team but that was after their pneumatic system was already working properly. We used a piece of tubing to extend the end to make it easier and safer to probe inside the robot.

1 Like
15

Thank you.

16

Thank you very much.

17

That’s innovative.

18

Good info. Thanks.

19

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