A 3D Printed Snake Automaton.
Introduction: A 3D Printed Snake Automaton.
Just prior to designing an enclosure for "A 3D Printed Snake Automaton", family, friends and followers who viewed the mechanism became mesmerized watching it in action, so mesmerized that they were disappointed that I would hide it from view in an enclosure. So here is "A 3D Printed Snake Automaton" for all to see in "open format" form!
During operation, this mechanism assembles two chains into one "pseudo rigid" chain to create a snake and raise it out of its cartridge. When completely assembled and raised, the mechanism mechanically reverses direction and disassembles the snake back into two chains as it lowers the snake back into the cartridge.
The mechanism uses a rotary gear carriage for mechanical reversing. When the carriage rotates to the ascend position, the carriage gears drive an ascend gear to assemble and raise the snake out of its cartridge. And when the carriage rotates to the descend position, the carriage gears drive a descend gear to disassemble and lower the snake back into its cartridge.
However, without intervention the rotary gear carriage will continually rotate via the gear motor and as such must be paused to drive the ascend and descend gears in order to assemble / raise then disassemble / lower the snake. To pause carriage rotation at the proper positions, the carriage wheel has two stop tabs; one for the ascend position and a second for the descend position.
A mechanical switch assembly moves a single pin alternatively between the ascend and descend carriage wheel stop tabs in order to pause the rotation at the ascend and descend positions. The mechanical switch is positioned by an arm attached to the chain drive sprocket that sets the travel limits of the snake as it ascends and descends.
At 6VDC, the mechanism draws an average of 15MA, low enough for solar powered operation which was one of my numerous design goals.
As usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to comment as I do make plenty of mistakes.
Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.8.0, and 3D printed in PLA on Ultimaker S5s.
Supplies
* Soldering Iron and Solder.
* Thick cyanoacrylate glue.
* Light machine oil to lubricate the gears, arms, slides and axles.
Step 1: Parts.
I acquired the following parts:
* One N20 100RPM 6VDC gear motor.
* One 4AAA battery holder with on/off switch.
* Four AAA batteries.
* One 6.35 by 10.3 spring.
* One R08 (11mm ID, 2.5mm Section) o-ring.
* 2mm diameter music wire.
The attached file "Parts.pdf" contains the name, quantity, infill, layer height and support of all 3D printed parts I printed for this mechanism. 949
Note parts with a ".3MF" extension are dual extrusion prints.
This mechanism is a high precision print and assembly using at times very small precision 3D printed parts in confined spaces with highly precise alignment. I printed the chains, gears, levers, arms, cams and wheels using the Ultimaker Cura 4.8.0 "Engineering Profile" on my Ultimaker S5s, which provides a highly accurate tolerance requiring minimal if any trimming, filing, drilling or sanding. However, prior to assembly, I still test fitted and trimmed, filed, drilled, sanded, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth using small jewelers files and plenty of patience to perform this step.
This mechanism also uses threaded assembly, so I used a tap and die set (6mm by 1, 8mm by 1.25) if required for thread cleaning.
Step 2: Pins.
The mechanism uses two metal pins (one 14mm in length, the second 8mm in length) for ascend / descend control. I made these pins from 2mm diameter music wire as follows:
* Used a cutoff blade in a hand held rotary tool to round one end of a length of the 2mm diameter music wire.
* Marked the music wire at 14mm from the rounded end.
* Cut off the 14mm length.
* Filed the cut end smooth.
* Repeated the previous four steps for the 8mm length pin. 632