Introduction: Laser-Cut Wooden 4 Axis Positioning System

The following instructable details the process of building a 4 axis positioning system (X,Y,Z+theta). While we leveraged this setup for an automata aquarium, it may be useful in your other projects as well.  Anyway, our build targeted modified Hitec HS-55 servos (see this other shamelessly plugged instructable), but servos of similar size should also be usable with similar steps.  Note that if another type of servo is used for this project, the CAD models for the 3D printed parts may need to be changed as well. This was part of a project for the spring 2012 Things That Think class at CU Boulder.

Supplies:
    1/4 in. basswood
    laser cutter
    3D printer
    4 sub-micro servos modified for continuous rotation and position feedback.

Step 1: Laser Cut Parts

Using a laser cutter, cut the pieces from the attached file laser_cut.DXF out of 1/4 in. basswood.  We recommend this material because acrylic and other plastics did not hold gear tooth shapes well when laser cut and, moreover, the basswood provided a good compromise between cut-ability and strength.  The laser cutter patterns are designed for a beam width of 0.25 mm. The units for the .DXF file are in milimeters

Step 2: 3D Print Parts

The following parts need to be 3D printed. The units for the .STL files are in milimeters.

Step 3: Install Wooden Gears to Servos

Press the three gears onto the output shaft of three of the servos.  If they do not press fit well, install a washer and screw to hold them in place.

Step 4: Add Sidewalls

Insert the 2 ft. long tracks and x rack into one of the rows on one of the side walls.  The teeth on the rack should face the bottom of the side wall. Press the other sidewall onto the other end of the tracks and x rack.  Ensure that the second sidewall has the same front-back and top-bottom orientation as the first sidewall, so that the x rack and both tracks are all parallel.

Step 5: Install Racks and Servos

First, place the cart on the tracks and x rack and install one of the servos with a gear into the servo slot on the bottom  of the cart to hold it in place. Afterwards, press the y rack cap onto the end of the y rack. Then, place the y rack in the cart and install one of the servos with a gear into the servo slot on the top of the cart to hold it in place. Next, press the z rack cap onto the end of the z rack. After that, slide the z rack through the y rack cap and install the remaining servo with a gear into the servo slot in the y rack cap to hold it in place. Finally, install the last servo into the servo slot on top of the z rack cap.  Be careful that the wires are correctly passed through their slot and are not pinched under the servo.

Comments

author
sitearm (author)2012-04-08

@DancingFish; Hi! Is it possible to add a short video of this positioning system in action? Your article is timely: I'd just heard of 4 axis machining rigs at a conference. Cheers! : ) Site

author
DancingFish (author)sitearm2012-05-05

Hi sitearm, we would love to post a video, unfortunately we had to return the arduino. You can see it working in the full aquarium automata https://www.instructables.com/id/Automata-Aquarium/.

author
bobwantzanapple (author)2012-04-08

could this be applied to CNC milling or 3D printing?

author

This could indeed be applied to CNC milling and possibly 3D printing. We decided to use the laser cutter because it provided a higher level of accuracy and detail than the 3D printer available to us.

author
CopterRichie (author)2012-04-08

What are the procedure for modifying a servo for continuous rotation? the one shown appears to be a 9G.

Thank you.

author
mikolynn (author)CopterRichie2012-04-08

https://www.instructables.com/id/Sub-Micro-Continuous-Rotation-Servo-Modification/
;)

author
rimar2000 (author)2012-04-08

Forgive my ignorance: what is that theta axis?

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