Involute gear without CAD skills?

3D Fabrication
1

I would like to make a small involute gear (to help my brother-in-law repair a favorite animated Christmas display). The gear is about the size of a quarter and about 3/8" thick. In the Z-dimension it is straight. But I lack CAD skills. If I could create a vector outline of the gear shape, would it be possible to import that somehow into Sketch-up or equivalent and “pull” it into a gear with depth?

Or is there some other easy way to get there?

Thanks,
Chris

2

This may help…
http://lcamtuf.coredump.cx/gcnc/ch6/

3 Likes
3

Thanks Brian! That’s a good treatment of gear design / teeth.

I have a gear that I need to replicate, so it doesn’t need to be designed, just modeled. That’s why I was thinking about a vector path … I can create a 2D scan of the tooth profile and create a vector replica. But I need a way to get it to a 3D model.

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It is relatively easy in Inventor to do what you are wanting to do. I can do it for you (aren’t I funny? I hope you don’t have a deadline), but if you’re up for learning by feeling around in the dark this is a very quick and dirty “explanation”:

  • create vector path (I would save to dxf/dwg) however you were going to. Make sure it is closed.
  • open Inventor, create a new part
  • create a 2D sketch, select a plane, import your dxf (there is some thought as to what plane to use for complex modeling, but I don’t know what your end use is…)
  • finish the sketch, you should now see your linework in the plane you selected
  • extrude, select the linework, input the thickness, and go!

There is a thought in my mind that a gear that is scanned and 3D printed (or otherwise repro’d) wouldn’t work well, but that is pure speculation.

5

If you have some useage of basic 2D cad this site walks you through drawing a gear in 2d; http://www.cartertools.com/involute.html

This produces a file you can laser cut from plastic pretty easily, and would be relatively easy to use with feature cam to mill out of aluminum.

If you were planning on using the manual machines to produce, then you don’t need a cad file, just the basic information about the gear to reproduce. And some tooling we don’t have (involute cutters).

1 Like
6

There’s a SketchUp plugin that will create the gear outline for you based on input parameters and you can then extrude to whatever thickness you want. I’ve modeled and 3D printed gears this way that worked well.

Info here: Drawing gears in Sketchup. | Capolight Electronics Projects.

1 Like
7

There is a program called “Gear template generator program” that will generate the gear if you give it the diametric pitch, pitch diameter, tooth spacing, number of teeth and the shaft hole diameter, and it will generate a sketchup file in 2D that you can import and expand to whatever depth you want. If you know that info I can plug them in and generate the file for you so you can import it to sketchup. I think you can actually use it on line at http://woodgears.ca/gear_cutting/template.html but I think you can only print it out to make a wooden gear. How do you intend to make this gear? What material?

1 Like
8

Inkscape has a gear profile generator. You can use this to make a wooden or plastic gear on the laser cutter.

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Online involute spur gear generator.

Creates a downloadable DXF file.

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Here is an online, interactive involute gear generator which will generate an STL file which you could then download and 3D print. X3D (3D DXF) export is also available.

http://joostn.github.io/OpenJsCad/

Just click on the link, edit the params, preview, and download to print.
Number of teeth:
Circular pitch:
Pressure angle:
Clearance:
Thickness:
Radius of center hole (0 for no hole):

Note: length units are in mm, not inches.

Uses Open JSCAD, a Javascript implementation of OpenSCAD (I believe).