In this Instructable, we'll be going through how to 3D print a piston, create seals using bathroom sealant, and assemble it to produce a working, air-powered actuator that can be used for a variety of projects. These are great for where you want to have moving parts, without extra electronics i.e., lifting arms or a makeshift crusher. The model I'm going to be assembling fits some quarter-inch tubing I had laying around and can attach to foot-pump to supply the pressurised air, but the model can be scaled and altered to produce stronger pistons and larger volume ones too. In my models, I have included a vent near the end of the case, so that the air can vent out the side and not fire the piston out of the case when high pressure is put in.
For this Instructable I used:
* A 3D Printer and filament
- I used a 3D Touch with PLA, but any printer/material should work, so its worth playing about with.
* Multi-purpose Silicon Bathroom sealant
- Must form Acetic Acid during curing as this means it is usable to create rubber with.
* Mixing cups and sticks
* Suitable Tubing
- You can create your own piston to fit any you have lying around, my model has an 8mm outer diameter input port.
Details for making your own piston are at the end
Step 1: Print Your Parts
First off, you'll want to print the component parts: The Case, The Piston and The Mold. These are fairly small, so I've put them in one STL file which should be ok for most build areas.
Mine were printed in PLA, at 0.25mm layer height with a raft, although other print specification will work too. Use the build profile you'd normally use for other parts.
Remove as much support as possible, however support inside the casing's input pipe is fine as long as air can flow through. There isn't any necessary finishing otherwise required.
Step 2: Make the Seal
Now, this step was only made possible after reading mikey77's Instructable on Sugru Substitutes (http://www.instructables.com/id/How-To-Make-Your-O...)
To make our seal, we'll follow this method by mixing a 1:2 Cornflour to Sealant ratio in some plastic cups, and making enough to fill the mold half-way.
Once the mix has been thoroughly mixed, it can be scraped out into the mould and the plunger section of the piston is then pushed into the sealant, within the cap, until it reaches the bottom and excess cleaned off.
This is then left to cure for a few hours.
After curing, the seal is then best loosened with a thin paper clip or similar before pulling the piston out, bringing the seal with it.
It's important that the "Ring" section is intact as this will form the seal.
Step 3: Lube and Assembly
Finally, the whole actuator can assembled with a little lubricant. I used Vaseline since I couldn't find any WD-40, and it forms quite a nice seal. Once again, it's your piston so feel free to test and see if it's slick enough for your project.
The lubricant is applied to the inside few mm of the casing and the seal. Once fitted it should move about fairly freely, but keep the seal.
Step 4: Completed - Want to make your Own?
So there you have it, one 3D printed, working, pneumatic actuator,
If you want to design you own its pretty simple.
1) Find the size of tubing you'll use
2) Decide how wide the cylinder will be and 3D model it with one open end, and a tube for the tubing at the top.
3) Design a piston to fit inside, leaving room for the seal
4) Make a simple mold for casting and print it all
5) Assemble accordingly.
Be aware that the piston may shoot out if there isn't a proper vent/stop at the end of the case.
Anyway, thanks for reading along, and I hope you enjoy your new Actuator. I'm entering the 3D printing Contest so votes would be greatly appreciated as would feedback, as this is my first Instructable