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I want to create a micromouse project for fun that use 2 20 mm x 8.5 mm (0.8 mm shaft) motors. I have my own PCB as base. I want its built-in gears will be attached to two 3D-printed wheels with gears at the back of the wheels at each side. I'm having hard time to start designing the gears since I couldn't find any tutorial.

(photo for reference and not mine) enter image description here enter image description here

My Question:

  1. How to design the gears at the back of the wheel? (I use Sketchup)
  2. Is 3d-printing such small objects possible?
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    $\begingroup$ designing is engineering. Is printing possible is here. $\endgroup$ – Trish Jan 31 '19 at 22:23
  • $\begingroup$ About gear geometry: youtube.com/watch?v=Q-XOM4E4RZQ $\endgroup$ – Trish Feb 3 '19 at 0:07
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    $\begingroup$ I would use OpenScad and probably a library to do this. $\endgroup$ – E Doe Feb 4 '19 at 8:58
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Designing gears is very difficult for a variety of reasons. Let me list what you should take into account:

  1. The shape of the teeth are very peculiar, trapezoid shape will not work as the meshing will not be constant. Exact shape is controlled by the pressure angle

  2. In lower number of teeth, teeth shape must be modified to avoid any locks, these are called cutoffs

  3. Reducing the amount of material to print requires careful design, most people simply place circles but they cause weak points.

  4. Herringbone and double herringbone gears improve meshing but are even more difficult to design.

For the reasons stated above, creating gears by hand is next to impossible without special tools. Luckily for those who are searching for it, there are systems that generate gears for 3D printing. This customizer has many options and is very open about the licensing, which is another issue with many scripts. For example, it is explicitly forbidden to print parts imported from the McMaster-Carr Catalogue.

If you use OpenSCAD, this library can create racks to go with the gears.

The parameters of the customizer are explained in the page. The script also contains explanations of every module and function.

Disclaimer: Both scripts are mine, yet I do not earn anything when people use them. I created the library when I was unable to find the gears I needed, published with a relaxed license to help others.

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    $\begingroup$ @CarlWitthoft Comments are transient and aren't meant for answers to the question. This would be better as a more detailed answer, explaining a little bit about the customizer. $\endgroup$ – Tom van der Zanden Feb 1 '19 at 22:03
  • $\begingroup$ Added more explanation about the process of creating gears. Better? $\endgroup$ – Cem Kalyoncu Feb 2 '19 at 16:17
  • $\begingroup$ @TomvanderZanden bump for Cem $\endgroup$ – Trish Feb 2 '19 at 17:21
  • $\begingroup$ @CarlWitthoft you had said something that was adressed, so I bumped you for Cem :P $\endgroup$ – Trish Feb 3 '19 at 18:36
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There are also several gear generators out there. Correct gear geometry is important for long life and noise reasons.

One thing to keep in mind is that iff you are able to print accurate gears it's easy to print herringbone gears which are not easily machinable with other techniques.

That should cover the how (use a generator and import the geometry). The "is it possible" depends on your 3d printing skills, if possible you need to be able to do 0.1 mm tolerances, elephant footing will make the gear unusable.

That said I was able to print some planetary gears 'in place' (ie. assembled on the print bed) using a raft to avoid fusion of the lower layers:

left: printed with raft, right: printed on build plate

Spinning the gear printed on raft: https://imgur.com/IRlulJF Spinning the gear without a raft directly on the print bed: https://imgur.com/0p02uKV

The first one is still on my work desk as a fidget spinner because it spins so nicely ;-)

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  • $\begingroup$ Can you explain the term " elephant foot" ? $\endgroup$ – Carl Witthoft Feb 1 '19 at 15:55
  • $\begingroup$ Sure! It's when your first layers squash out. Mostly that's caused by too low nozzle height or to high bed temperature. $\endgroup$ – fho Feb 2 '19 at 17:00
  • $\begingroup$ Example pictures and solutions: google.com/amp/s/m.all3dp.com/2/… $\endgroup$ – fho Feb 2 '19 at 17:21
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    $\begingroup$ I bought a program to make gears and chain gears, but this one looks great! $\endgroup$ – Fernando Baltazar Sep 18 '19 at 18:33

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