Small and reliable servo controlled valves can be easily 3d printed. They are suitable for controlling air or water and all kinds of robot projects.

Because they use standard RC micro-servos, they can be controlled by a standard RC radio setup.

They can also be easily controlled by a microcontroller such as an Arduino or Picaxe.

Intro pic shows the valve controlling a 3D printed artificial muscle.

Step 1: How It Works

The 3D printed valve is actually two valves that are controlled by one micro servo. When the cam (gray) is rotated to center, both valves are closed. From there, either one can be turned on, one at a time. The cam followers (black) push on the silicone tubing to compress it and create simple pinch valves.

The servo valve is quite efficient in that it is about the same volume of two 12 volt solenoid valves that handle the same pressure. It works efficiently at 20 PSI of air pressure and it has been tested at up to 30 PSI. It has also been motion tested and after more than 4300 on-off cycles it did not show significant signs of wear on the moving parts.

It is also considerably lighter than two solenoid valves and uses much less energy to operate. Once actuated, the valves can be left open or closed without using power.

Step 2: Supplies

I used a Maker-bot Replicator 2 to print the parts in PLA plastic. Other filament 3D printers could be used.

PLA filament

four 2-20 x 1/4" round head screws

Futaba S3110 micro- servo
If you cant find this exact servo, you will have to substitute another Micro-servo of the same size or cut off the servo part of the base and attach your own design for a servo holder.

1/8" O.D. Silcon Med-X silicone tubing and 1/16" I.D. nylon tube fittings-available from:

http://www.usplastic.com

Step 3: Print the Parts and Assemble

For the cleanest and most precise prints, print the three STL files separately. Make sure the cam followers are printed laying flat so that the curved end has smooth layers in line with the cam.

Replicator 2 Settings
These settings work well for a Replicator 2 and PLA. If you use a different printer, you may have to play with the settings.

Infill: 10 per cent
Shells: 2
Layer Height: .2mm
Temp: 230 C
Speed Extruding: 90 mm/s
Speed Traveling: 150 mm/s
No raft and no supports.

Assemble
Clean off any blips or protrusions to make sure the cam followers move freely in their sockets.

Step 4: Valve Control With a Microcontroller or Radio

Radio Control
The servo controlled valves can be connected to a standard RC receiver. The on-off points can then be marked on the RC transmitter to allow the control of animatronics, robots, or other devices.

Control By Microcontroller
Step 5 pic shows the schematic for controlling the valves using a Picaxe Microcontroller. Pic two shows the circuit board. A separate battery or power supply should be used to power the servo to avoid interference with the Picaxe.

Picaxe Code
Here is the programming code used to actuate the valves.

This program tests the valves with continuous on-off cycles and displays the number of cycles on a PC.

'o8m2 futaba servo valve cycle test
disablebod
high c.4
high c.1
'servo c.2,151 '77-225 initial position, 151 middle
b0=0
w1=0

main:
servo c.2,156
servopos c.2,110 ; move servo to left
pause 400
input c.2
pause 1000

servo c.2,210
servopos c.2,190 ; move servo to other end-right
pause 600
input c.2
pause 1000
b0=b0+1
w1=w1+1
pause 50
debug
pause 50
goto main ; loop back to start

Step 5: Other Possibillities

Step 6 pic shows one of my earlier designs for valves that are stack-able in several directions.

Other Valve Designs
Smaller volume valves should be possible. It should also be possible to enlarge this valve design to make valves that use larger diameter tubing. The base would have to be modified to accommodate larger servos.

Gear Motor Valves
Gear motors could be used to turn a longer series of stacked cams which could control multiple valves in a specific sequence.