DIY PVC pneumatic cylinders???

[Lornie McCullough]

Have you made your own pneumatic cylinders using PVC? Either for automated operations (blast gates, etc.), or for hold downs for jigs and such? It seems like it should be very easy and cheap to do. (with the possible caveat of being limited to lower pressures for safety?)

What is your experience? How did you put them together? How did you use them?

Lornie

[Jim German]

Would there be much point? Looking on ebay you can get pneumatic cylinders for quite cheap.

[Lornie McCullough]

I visited a cabinet shop once where the owner had made use of homemade pneumatic cylinders to help around the shop. The one that sticks in my mine was a pneumatic assist to a homemade panel saw (the her-saf kind). I suppose you could also use a pulley and sash weight for a panel assist..... (I am not looking for a panel assist....)

I guess the point would be innovation and imagination. And cheap. Without the usual limitations.

Lornie

[Jim Neeley]

Lornie,

The engineer in me says it'd be very doable.. subject to your ability to make them to high enough tolerances to avoid leaking air. Lacking that you'll need something more akin to a regulator to control them rather than an open-close valve or have a "catch" to hold it afixed in a location.

Jim

[Jerry Bruette]

I work with and repair air cylinders every day at work. Maybe I'm not thinking out of the box, but what would you use for a piston, cylinder rod, and rod seal? Curious how you'd mount them too.

Jerry

[Alan Schaffter]

Tried it, didn't work well, too many leaks, too much trouble. Needed bi-directional cylinders which are even harder to make since they need piston and rod seals. Went with Bimba cylinders from Ebay for my autogates.

Experimental cylinder on the left:

http://www.ncwoodworker.net/pp/data/1329/medium/P21500741.JPG

[Steve Rozmiarek]

Alan, that is an interesting valve assembly, what is it?

[Steve Milito]

Tried it, didn't work well, too many leaks, too much trouble. Needed bi-directional cylinders which are even harder to make since they need piston and rod seals. Went with Bimba cylinders from Ebay for my autogates.



How do you actuate them?

[Joe Hillmann]

Right now you can find smaller cylinders on ebay for $5 each so I don't know if you will save anything other than being able to say you made it yourself. You can easily convert screen door closers into air cylinders by removing the set screw and re-threading the hole to 1/8" pipe thread. You have to thread it in an upside down position so any metal chips fall out instead into the cylinder. Since it has a spring inside it will pull itself back and you can control it with one ball valve and a very small bleed hole drilled in the pipe between the valve and the closer. To push the ram out you open the ball valve and leave it open (air will be leaking out of the small bleed valve but not enough to matter) to pull the ram back in shut the ball valve. Air will continue leaking out of the bleed hole and the spring will pull the ram back in.

With this set up you only have any real pressure in one direction.

[Alan Schaffter]

Alan, that is an interesting valve assembly, what is it?

It is a typical pneumatic solenoid valve manifold from some type of automated machine. Solenoid air valves come in many configurations. This is just one available on Ebay and how I bought many of the valves for my DIY electro-pneumatic autogates. These are 5-2 (5 ports two way) valves that are needed for bidirectional cylinders. I disassembled the manifold and put "cheek" blank-outs on each side to make a single valve. Some of the valves I bought were of the single, standalone type- I bought what was available and the best price I could find. I would have preferred all individual valves since they are smaller and lighter. Though more work to adapt to my needs, valves were often much cheaper when purchased in manifolds.

L. - single solenoid valve, C.- valve and ported body removed from manifold. R. - valve ready to go with plexi cheek plates, quick connect right angle inlet fitting w/flow restrictor and nylon barbed hose fittings installed.

http://www.ncwoodworker.net/pp/data/1329/medium/IMG_2991.jpg

Close-up of valve and ported body after manifold disassembly:

http://www.ncwoodworker.net/pp/data/500/medium/P2150076.JPG

Close-up of blank-out:

http://www.ncwoodworker.net/pp/data/500/medium/P2180006.JPG

Upgrading manual gates to auto-gates with the addition of bi-directional (Bimba) pneumatic cylinders:

http://www.ncwoodworker.net/pp/data/500/medium/P3080015.JPG

Typical single valve installations. Not fancy but they have been working great for years:

http://www.ncwoodworker.net/pp/data/500/P4280025.JPG

http://www.ncwoodworker.net/pp/data/500/P4280020.JPG



How do you actuate them?

They are powered by 26VDC from a transformer and triggered by current sensing switches at each machine outlet. If the current sensor switch senses current flowing to the machine (a torroid coil generates a slight current and causes an internal solid state switch to close) it sends power to the solenoid valve which changes state and allows 15 psi shop air to power the cylinder (and blast gate) to the open position. (the DC is triggered as well) When no current flows and the valve is in the unpowered state it ports air to close the cylinder and the gate. (DC is NOT triggered off)

Current sensing switch mounted in a box adjacent to the outlet box (not visible):

http://www.ncwoodworker.net/pp/data/500/medium/P50400021.JPG

[Lornie McCullough]

[QUOTE=Joe Hillmann;2079150] You can easily convert screen door closers into air cylinders by removing the set screw and re-threading the hole to 1/8" pipe thread.

Joe.... this looks like it will be promising to explore.

Alan, I find all of your posts inspirational.

As woodworkers, we almost all have compressed air in our shops. I'm interested in hearing your stories of how you have made compressed air work for you (other than the obvious staplers, nail guns, blow nozzels, and spray equipment ).

Lornie