I love 3D printing, and I really like to push its limits as a technology. And one of the most special feature's about it is being able to print different parts in place. So a useful example that I thought of is a one-way valve. In my case, I made it at Techshop on one of their MakerBot Replicator 2s =)
Step 1: Designing the Valve
So basically what needs to happen here is that the ball bearing inside needs to seal if pushed in one direction, but still allow flow if pushed in the other.
So basically I start with a hollow tube that narrows done at both ends into little cups with a hole through them. One end will have an extra X shaped cut that allows flow even if the ball bearing is pushed in that direction. The size of the cups needs to be slightly larger than the ball bearing itself about 0.5-2mm depending on the accuracy of your printer.
Also the tube where the ball bearing resides needs to be slightly larger than the "cups" because air/water needs to be able to flow past the ball bearing and the ball bearing itself needs to be able to move freely between the two ends. Finally you'll also want to fillet the inside so that the ball bearing if pushed in either direction by a change in flow will immediately seat in one of the "cups."
Step 2: Assembly
Okay now here we need to place the ball bearing level with the bottom of the valve. This is because we’re using a fused deposition material printer and we can’t use supports because we can’t really get them out of the valve afterwards.
Also make sure that it makes this + sign and not an X sign when printed. The X has free floating parts that cannot be printed without supports (think about the top part of the X). The + sign has some hanging parts, but if you don’t make them too big, it’ll still be okay.
Step 4: Freeing the Ball Bearing!
Use something thats just the right size to poke the ball bearing free. I actually accidentally poke it too hard, and wedged the "poker" next to the ball. This is bad, because it deforms the ball bearing, which reduces the quality of the seal. So be a bit careful.
Step 5: Sweet Functionality!
Here it is! I tested it out using my water faucet by turning it on and leaving the water pressure the same. As you can see with the first image, the water runs out pretty smoothly. But when I flip it over to the other side, there is a significantly higher amount of back pressure, spraying me all over in fact. It's not a perfect one-way valve, mainly due to the FDM style printer and the 2mm clearance for the ball bearing. But if you had a better printer that provided a smoother surface finish, higher accuracy plus easy to remove supports, you could get a very high quality one-way valve from this design.
I've also provided the STL file in case you wanted to skip the cadding part or have a closer look at the design. Both ends are one inch in diameter. Have fun!
PS: If you ever need to hire a CAD designer or want something custom made, feel free to contact me at =) CatalystFrame.com