Shop-Made Pneumatic Cylinders From PVC And Plywood

You see a lot of pneumatic actuators in industrial automation, and for good reason. They’re simple, powerful, reliable, and above all, cheap. Online sources and fluid-power suppliers carry a bewildering range of actuators, so why would anyone bother to make their own pneumatic cylinders? Because while the commercial stuff is cheap, it’s not PVC and plywood cheap.

Granted, that’s not the only reason [Izzy Swan] gives for his DIY single-acting cylinder. For him it’s more about having the flexibility to make exactly what he needs in terms of size and shape. And given how ridiculously easy these cylinders are, you can make a ton of them for pennies. The cylinder itself is common Schedule 40 PVC pipe with plywood endcaps, all held together with threaded rod. [Izzy] cut the endcaps with a CNC router, but a band saw or jig saw would do as well. The piston is a plywood plug mounted to a long bolt; [Izzy] gambled a little by cutting the groove for the O-ring with a table saw, but no fingers were lost. The cylinder uses a cheap bungee as a return spring, but an internal compression spring would work too,. Adding a second air inlet to make the cylinder double-acting would be possible as well. The video below shows the cylinder in action as a jig clamp.

True, the valves are the most expensive part of a pneumatic system, but if nothing else, being able to say you made your own cylinders is a win. And maybe you’ll get the fluid-power bug and want to work up to DIY hydraulics.

Thanks to [Shawn Gorman] for the tip.

26 thoughts on “Shop-Made Pneumatic Cylinders From PVC And Plywood

  1. Substitute polycarbonate for plywood, and this was the barrel advance cylinder I used on a “potato chaingun” I attempted about 18 years ago. :) That was really heavy, and a failure, but this part worked pretty well. Too well.. My 1.5in PVC version of this generated like 200lbs of pushing force, which was enough to destroy itself if left to impact the endstop. The solution was to not drill a relief hole on the opposing end, which made the opposing trapped air into a spring.
    The ID of PVC foam core pipe can vary dramatically between runs, and be pretty rough. Save yourself a lot of trouble and measure/look at it.
    PVC also does tend to fail in dramatic and dangerous ways, but a couple wraps of good duct tape will keep most of the shrapnel contained. Tested.
    Ok.. I’m done.

  2. $5 for a blow gun brings the cost of valves down. Making your own spool valve wouldn’t be that difficult either using the same wooden piston construction or casting epoxy ones so you can use smaller pipe.

      1. I think I had one that went to 100, but in either case, I don’t think you need the max rating for something like pneumatic work holders. 30-40lbs seems plenty (but I think he’s getting close to 3X that), especially if you’ve got some rubber or friction tape on the working face.

  3. Izzy’s youtube channel (especially the earlier videos) were very exciting. Dangerous, but exciting. He’s a wildman and I like it. Above all, he solves problems in unique ways. He thinks out of the box.

    1. True, but he is running 60psi. Schedule 40 2″ pipe has a minimum burst rating of 890psi and an operating pressure of 166psi. If that is too tight a spec, you can get the same force with a 3″ pipe (840 psi burst, 158 operating) and 30psi.

      1. The problem isn’t bursting due to overpressure (unknowable in practice without actual failure, so max allowable is generally some fraction of a calculated value), but due to a) the significant stored energy in compressed gasses, and b) the propensity of PVC to undergo brittle failure, in particular due to impact, in particular where there is already damage (cuts, scratches, abrasion, any stress riser). This isn’t a big deal with liquids, as there is little stored energy in the working fluid.

        The nature of pneumatics is that impact and abrasion are pretty much going to happen.

        You need to balance risk of failure against the penalty. Not worth it.

      2. The burst rating is for (mostly) non compressive fluids and while the pressure “ratings” are the same, the fail modes are not. Importantly though, what happens when you accidentally strike the cylinder while it is under load or the force comes from the other direction as opposed to the air supply side or the cylinder is worn or internally and not visibly scratched, etc? There is a reason cylinders use inexpensive aluminum tube as a cylinder material because they don’t fail in the same way that PVC does (and can take significantly more pressure as well).

        I like the concept of what they are doing but this is another example of going so far in the “make it as cheap as you possibly can” that you start to go beyond and start to sacrifice safety just to make this “work”.

        Just buying a cylinder is probably cheaper in almost every case and will result in a significantly better end product.

        What happens when they try to make a 6″ nominal cylinder next? Might want to explore those PSI ratings really carefully if you are that intent on still doing so with plastic cylinders.

        1. Or just use HDPE pipe instead of PVC. It costs a bit more but it deforms and tears rather than fragments. It is commonly used for professional fireworks mortar tubes. It can take a lot of abuse.

  4. How about a 50 mm pipe around the 40mm pipe, as a shrapnel capturing shell. A pressure bread off hole will be nessasary, either in the wood or the pic. The final product could look as clean and be almost as simple as the unprotected version.

  5. > You see a lot of pneumatic actuators in industrial automation, and for good reason. They’re simple, powerful, reliable, and above all, cheap.

    From what I’ve heard in the industry, it’s the most inefficient and expensive kind of power to supply…

    1. Losses, losses everywhere, ’tis true. Lose on compression (adiabatic heating of the fluid). Lose at point of utility (adiabatic cooling of the fluid). Lose in transport (friction/flow losses). Lose at the system level (leaks; head space losses, and so on). And it goes on…

      But actuator size, speed, and force are an unbeatable combination at any price (for now… pure electric is catching up), and can’t even be approached with any other technology without appending zeroes to the price. Delivery of power is reliable, simple and cheap .Maintenance is reasonable, and, in many cases, can make up for the cost difference in energy.

      Not the choice for precision positioning or finely controlled speed, but Bimba is still in business because the overall system (install, operate, maintain) is the least expensive for many applications.

      1. > Not the choice for precision positioning or finely controlled speed

        You would be surprised what can be achieved with some simple encoders and two variable flow valves when using hydraulics. For pneumatics yeah, too much springiness.

    2. Yes, compressed air is quite inefficient due to the thermodynamics. But it has a high power density and low weight. If you have a danger of explosive atmospheres it is also a very good choice.

  6. I keep wanting to design a water pump and I would use PVC for that, but I would 3D print the end caps and valves. Very similar though really. BTW if I had the CNC router I may go a different route (no pun) with the end caps etc. It all depends on what you have on hand and where you comfort zone is with what you have.

  7. So … does anyone have a link to a reference for aluminum tubing and max safe working pressure? I mean, for say, 6061 extruded aluminum tubing, a 1/8″ thick wall can safely handle xx PSI?

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