Jul 132015

Before you read on, please make sure that you have seen part 1 which introduces my Online Involute Spur Gear Builder. This second part addresses DXF export and compares the generated tooth profiles with the output from a commonly used OpenScad script.

DXF Export

Unfortunately there are many variants of the DXF format and not every tool is capable of importing the dxf output generated by the tool. Here are a few pointers:

  • Inkscape: Inkscape is a free, open source vector graphics tool that can import the generated dxf output without any issues. Inkscape’s native format is svg but it also supports many other output formats that are useful when dealing with other tools.
  • Illustrator and VectorWorks do not seem to recognize the generated output. Lael and Jeroen Donker reported workarounds (thank you, both!):
    • Lael: Just an update for anyone else trying to use illustrator or having issues importing into drawing programs. I downloaded Dassault draftsight, opened the dxf generated by this generator, then saved it as 2009, 2010 and 2013 dxf. 2009 and 2010 opened fine in illustrator.
    • Jeroen Donker: I found that the dxf output file can be opened in Inkscape (freeware on all platforms) and then saved in any vector format (I use eps) Opening the file in Adobe Illustrator is an easy next step.

Generated Output Comparison

It is interesting to compare the generated output with that of other tools. In particular this makes it quite easy to see when the undercuts become relevant. For the following I used Leemon Baird’s featured Public Domain Involute Parameterized Gears for OpenScad. Upfront I want to clearly state that this comparison by no means is intended to diminish Leemon Baird’s code. Like many other tools it simply does not cater for undercuts which in most real-world scenarios can be ignored. If undercuts are not an issue Leemon Baird’s tool is a perfect choice.

For the comparison I chose a pressure angle of 20°, 8 mm circular pitch, no clearance, and no backlash. For reference here is the scad file with the configuration for the 6 tooth gear and the resulting dxf file generated by Leemon Baird’s script.

The images below (excerpts from the svg file InvoluteGearComparison.svg) show the tooth profiles for tooth count 40, 20, 10, and 6. The thicker black background lines represent the output generated by Leemon Baird’s code. The thinner red lines in the foreground are the tooth profiles generated by my online generator:



As expected the two profiles match almost exactly for large tooth counts. It is interesting to see that even for a tooth count of 20 there is a slight undercut visible. I expect in real live this would not matter since it is compensated for by a non-zero backlash.



  6 Responses to “Online Involute Spur Gear Builder – Part 2”

  1. Hi Dr Rainer.

    I am trying to make a rack and pinion gear for fun….I cant seem to be able to do this.

    I have gone through your instructions, but it keeps giving me an error.

    What am I doing wrong…..I am using a mac?

    Kindest regards

    Tony Watts

  2. Are you using the Safari browser on the mac? I am fairly confident that my tool worked in Safari in the past but I just tried it out again and saw it crash. Please use the Chrome browser (https://www.google.com/chrome/browser/desktop/) instead.


  4. Hi Rainer,

    I just wanted to say that I’m really glad to have found your involute gear builder. It is the best I have ever seen. I’m on Mac, and it’s the only thing I’ve found to work on OS X.

    It would be great to chat with you if you have some time!

    – Noel .oO(http://teknoel.com)

    P.S. Cool blog!

  5. I actually think Trinity's slightly overrated as well – had a really good meal there a couple of years ago, but the couple of times I've been recently, the cooking's been nice but not really good, and service has been a bit weak.

  6. Hi Dr. Rainer Hessmer
    Thanks for that very fine tool. Unfortunately in AutoCad 2017 (and 2014) I can not open the dxf file, it says “Tabellenmarken fehlen auf Zeile 32, ungültige oder unvollständige DXF Eingabe ,, Zeichnung abgebrochen”
    Do you have a workaround?
    Hubert K.

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