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Laser-cut Pinch Valve

by nickjohnson, published

Laser-cut Pinch Valve by nickjohnson Oct 8, 2011

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Description

This is a pinch valve for 6mm silicon tubing, made from laser-cut 3mm acrylic, stacked and held together with machine screws. It's ideal for controlling the flow of air, water, fruit juice, hard liquor, or whatever you desire. It's ideal for controlling the flow of stuff you don't want to risk contaminating with a regular valve, and as a result it's intrinsically food-safe.

Power and control is provided by a lightweight '9g' hobby servo; the silicon tubing is simply a push-fit into the top of the valve arrangement.

The photos and video are of an earlier prototype; the uploaded design is slightly refined, but functionally identical.

You can see it in action here: http://www.youtube.com/watch?v=4raXnoKUtow

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No, a 3d printed version would work fine. I only design for laser cutters because that's what I find most convenient.
Is there any reason this couldn't be 3D printed rather than laser cut?
Metric machine screws from here:
http://www.boltdepot.com/Metric_machine_screws_Phillips_pan_head_Stainless_steel_18-8_2mm_x_0.4mm.aspx

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Instructions

Bolts must be at least the length specified, but can be longer. If you find M2 screws longer than 12mm for an affordable price, let me know, though!

The servo I used is a Hextronik HXT900, but pretty much any cheap 9g micro servo will work. Some may require some changes to the bottom 2 layers to fit their housings.

  1. Cut the parts out of 3mm acrylic with a laser-cutter.
  2. Attach your servo with M2 machine screws to the bottom-most layer (the one with cutouts for the top of the servo and the small holes for the screws. The screw head should be on the acrylic side, with the nut under the servo mount.
  3. Lay the second and third layers on top of the first. Take a servo horn and cut the end off so it will fit within the cutout made by the third layer.
  4. Screw an M2 machine screw through the horn about 8.5mm from the center, with the screw head facing down - eg, so the screw will be 'upside down' when attached to the servo.
  5. Connect the servo to your device and set it to the counter-clockwise-most position. Attach the servo horn so it's parallel with the body of the servo.
  6. Now start assembling the body of the valve from the other end. Put M3 screws through the corner holes of the top 3 (identical) layers. Next, place flat washers on top of those, then the third, second, and finally first (with the servo attached) layers. Attach the M3 nuts and tighten.
  7. Turning the valve right-side up, drop the 3 plastic rollers onto the shaft formed by the M2 screw coming out of the horn. Take an M2 nut and screw it down a little, not so far that it prevents the rollers from turning. Use glue or epoxy to hold the nut in place.

Congratulations, you've assembled a pinch valve! Give it a try!

Is there any reason this couldn't be 3D printed rather than laser cut?
No, a 3d printed version would work fine. I only design for laser cutters because that's what I find most convenient.
Metric machine screws from here:
http://www.boltdepot.com/Metric_machine_screws_Phillips_pan_head_Stainless_steel_18-8_2mm_x_0.4mm.aspx
Stupid question, but I'm assuming that the scale to print is 1:1 units to mm, I plan on using this for a final project so I need it to work
Hey, I've built this one but it's not quite working. I think it might be the tubing, got any advice on that? Do you have specification for the tubing you used? Thanks!
You want the very flexible, thin-walled silcone aquarium tubing - not the thick-walled, tough plastic stuff. Where did you source yours?
I got mine from a medical supplies store (Clear Plastic (PVC) Tubing 3/16" I.D. x 1/4" O.D. (wall thickness 1/32")).

Also, I didn't use the washers from step 6, do you think they may make a big difference?
Thank you very much for the quick answer!
You could conceivably control the flow rate by opening it half-way; I haven't tried. How accurate your dispensing is depends on how reliable your flow rate is and how accurately you can measure what's dispensed. The valve itself opens and closes very quickly.
Thanks. Have ordered some servos so will give it a go. Will let you know the results.
Can you change the flow rate or is it just on/off? How accurate did you estimate you could dose?
Love it!

Where did you get the pump you use in the video?
It's the mechanism out of a battery powered aquarium pump (yes, they exist). They're pretty useful, because they run off 1.5 or 3 volts, are cheap (this one cost me $10), and as you can see from the water levels, have a decent flow rate.
Very cool. The medical profession and the cocktail robotics enthusiasts will both appreciate this!
Cocktail robotics is exactly what I built it for. :)
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