Homemade silicone O-rings and tubing

Make your own O-rings and tubing from silicone!
The object in this picture is a homemade submersible camera housing, made possible by the silicone O-rings.  (my next instructable will be the camera housing)

Quick and dirty explanation: Inject silicone adhesive straight from the tube with a caulking gun into clear Vinyl tubing, let it cure, blow the silicone out with compressed air, cut the silicone to length, re-glue it to form rings. If you want tubing, blow out the silicone before it cures...
This instructable will not only show how to make the O-rings and tubing, but go into detail about the way silicone adhesive behaves so you can exploit it, and make even more things!

Step 1 Materials

The primary material is Silicone adhesive that comes in tubes for caulking guns.

1. THERE IS A DIFFERENCE AMONG SILICONE TYPES. DO NOT USE "Silicone II", it is not pure Silicone, and will not behave as predictably as "Silicone I" , (or 100% silicone). The black Silicone is from ACE and is my favorite. Clear GE Silicone 1 is great too.

2. Clear Vinyl tubing. This is what you will be pumping the silicone into, it's the mold for the O-ring and tubing. The "I.D." or inside diameter of the tubing will be the "O.D." of the Silicone O-ring you are making.

3. Masking tape, compressed air, sharp knife, high quality caulking gun, about a week of cure time.

Comments

[gabdab]

Would it be possible to extend your procedure to make optical fibre ?
Crystal clear silicone and teflon tape on the outside should work ..

[thedanger]

you can add corn starch, like in mike77's instructable, it will speed up the cure time dramatically. here is the link to it http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/

[$0m3_0n3]

it sounds good, but how do you get it in the tube after it's mixed? I really want to try this

[CaptainChrisso]

I have since tried mixing the corn starch with silicone, and it does cure much faster, however there seems to be some weakening of the material. It doesnt stretch as much. If I were going to mix starch with silicone to use in o-rings, i would use an empty caulking gun tube: mix the starch and silicone very fast, and spoon it into the empty tube, put the piston thing in and then fill the vinyl tubing.
Also, roaches like to eat silicone cured with corn starch!

[CaptainChrisso]

Wow, that corn starch sure is an unexpected curing agent - and with all the messing around I do with silicone, I will give it a try, thanks!

[kebmoore]

How does the cost of this method compare to buying pre-made O-rings? I have a project in mind that requires 3-4 O-rings of different sizes, and buying a pack of 50 to use 2 of a size seems wasteful.

[CaptainChrisso]

If you can get the o-rings you need in a kit, go for it! My method is more time consuming than it is expensive, and gives you large o-rings that you would not be able to buy off the shelf. Regular o-rings will probably be a stiffer kind of rubber / nitrile, my silicone ones are very soft and flexible, yet seal irregular surfaces better. What kind of project are you doing?

[kebmoore]

I am planning to build a pneumatic spud-gun with a high-flow piston valve. I need a couple of O-rings to seal the piston in the valve chamber that will allow free movement of the piston when triggered. The groove in the piston will be 1.6 inches (the OD of 1.25 inch Sch 40 PVC), and the valve body is 2.05 inches (the ID of 2 inch Sch 40 PVC).

I was thinking of using standard Buna-N -326 O-rings, but places like McMaster-Carr sell them in packs of 50. Granted, the cost is only $6, but it seems like a waste to use 2 out 50. Your method would allow me to make only what I need. Plus, if I needed different sizes, I wouldn't have to buy another 50.

[CaptainChrisso]

OK I'm jealous of your project! Designing that piston mechanism sounds more fun than shooting the spud gun, but that's just me... The silicone o-rings may not work. (if i understand your plan correctly) First I think they will "fart" air if they are not under enough pressure from being squeezed between the groove and the inner wall of the larger pvc pipe... but if they are tight enough, they will not slide easily, so they may need to be greased. But - the inner walls of pvc pipes are not extruded to the same precision as the outside, not perfectly round, so a stiffer hard rubber o-ring still may not seal perfectly.
Maybe make some piston rings out of pvc, like an automotive piston, and bed them in the grooves with silicone?
Let me know how it turns out!!

[kebmoore]

I am a little worried about finding the best durometer for the O-rings. As you pointed out, I need something that will be stiff enough to hold up to 60+ psi and compressible enough to seal the imperfections between the PVC pipes. I think it likely that I want to go softer and use backup rings to keep the rings from being blown out.

The project has been in the planning phase for a long time. I also get as much joy from the design and build process as I do from using the results. I keep picking up ideas that will make the project more affordable and easier to make, ideas like making my own O-rings. When it gets built, there will be an Instructable to document it.

[clemsonguy1125]

 Thanks for posting, this is a great instructable, I wish I found this when I was building a nerf vortex launcher, I never could find large orings  

[rimar2000]

Good instructable!

I had been contemplating to do a circular groove in a piece of soap and fill it with silicone, but this method seems much more practical. Except the fact that we have to wait that long. Do not you can make a small paper tube to dry faster? For unmolding, wet the paper and wait a few minutes to soften ...

[CaptainChrisso]

Thanks rimar2000, I like the soap idea!
I thought about making grooves in MDF with a router to make a channel for the silicone, and using a straight edge to level off the silicone, and the MDF will breathe enough to let the silicone dry quickly. The orings wouldnt have a round profile though. Paper is great too, in fact i cover large square floor tiles with craft paper, and squeeze silicone between them to make sheets of silicone to build stuff out of.
Woo-hoo!

[maxstevenson]

What a great way to make big O rings. I'd sure like to see how you made that underwater camera housing, too. And some underwater pictures! I bet it would get featured if you posted some underwater pictures.

ps (i think it is spelled vinyl?)