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I have a tiny tube that sprays lubricant but I need it to move between some holes in a line. The total distance is only 10 inches.

So imagine the holes like this:

[ o o o o o o o o o o ]

And I need to move the lubricant tube between them.

I think I need a linear actuator to move the tube, but it doesn't need to be strong at all (less than 1 lb of force) or very accurate. If it lubricates a little bit off center it doesn't matter.

My issue is that linear actuators are so expensive! I'm currently leaning towards building one with Knex or Lego Technic and a servo. But does anyone know of a cheap/weak/inaccurate hobby option for less than $30?

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closed as off-topic by brhans, Scott Seidman, Matt Young, uint128_t, Chris Stratton May 1 '17 at 4:42

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  • \$\begingroup\$ Shopping is off-topic. \$\endgroup\$ – brhans May 1 '17 at 1:35
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    \$\begingroup\$ This is off-topic. But consider a belt-sled system to translate rotation motion into linear motion. Ya know, like a 3D printer. But instead, it's a 1D printer. 1/3 the price... \$\endgroup\$ – uint128_t May 1 '17 at 1:55
  • \$\begingroup\$ @uint128_t That is a great idea and I actually already have the parts for that. Thanks! If you post this as an answer I'll mark it. I'm laughing at myself for not thinking of this. :) \$\endgroup\$ – CornSmith May 1 '17 at 2:34
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    \$\begingroup\$ I'm voting to close this question as off-topic because it is a mechanical design problem rather than an electrical design problem. \$\endgroup\$ – Chris Stratton May 1 '17 at 4:42
  • \$\begingroup\$ Arrange 10 holes in a circular arc and connect circular arc to the linear arrangement via 10 flexible tubes. \$\endgroup\$ – Chu May 1 '17 at 9:03
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A hobby micro servo and a fabricated rack and pinion with a worm gear.

Or rip it out of a dead cdrom. Dime a dozen.

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  • \$\begingroup\$ A hobby servo won't begin to have enough travel, unless you remove the endstop and modify it into a DC gear motor with goofy drive electronics. \$\endgroup\$ – Chris Stratton May 1 '17 at 4:42
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worm gear is good but long, and you still need a datum optical sensor.

Also a cog belt drive from a stepper motor is very accurate with one optical end-stop for calibration by design. these are all used in any cheap printer or scanner. Controller is simple if you can program a uC card with motor driver. Otherwise, beyond scope of this questioner.

Stepper drive cards are usually direction and step# or step in/out from "home" sensor. Pulley size & steps per rev determine resolution.

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