Help on drawing a worm gear with its involute gear

[franceecad]

Dear all,
I beg your pardon, but I could not make this:

An example

Worm_Gear_and_Pinion.jpg (40.74 KiB) Viewed 6612 times

Source: https://es.wikipedia.org/wiki/Archivo:Worm_Gear.gif


I've tried to adapt an involute gear to an existing thread from a fastener M8, but it seems impossible to match.

This is what I achieve at best.

Selection_004.png (100.95 KiB) Viewed 6610 times

Do you suggest that I should continue trying or is there a better approach?

Thank you!

This is my About:
==============
OS: Ubuntu 16.04.2 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.16.6710 (Git)
Build type: None
Branch: releases/FreeCAD-0-16
Hash: f8eca0f9311f07c125dd6742a607724c1fa0b77c
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

[salp]

Do you need an accurate model to 3D print or just an approximation?

I created a rough model by using the same tooth pattern for the the pinion and the gear (see the attached FreeCad file).
Hope that helps.

Screenshot at 2017-06-06 20-54-19.png (178.71 KiB) Viewed 6609 times

Worm_Gear_and_Pinion.fcstd

(432.57 KiB) Downloaded 353 times

OS: Linux Mint 18 Sarah
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.11236 (Git)
Build type: None
Branch: master
Hash: 255b28138f6d512ce450e782a23c8cb739b0b306
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.1.0

[franceecad]

Many thanks for your help.

My intention is 3d print this model. Perhaps it would be a bit easier if there is a way to move objects with the mouse, constrained to a working plane, but I could not find it.

[UR_]

Hello franceecad,
some weeks ago, there was a similar question on this forum.

Please have a look.
https://forum.freecadweb.org/viewtopic.php?f=3&t=13906

[franceecad]

Thank you, UR_...
Amazing! I did not find the topic

I will definitely investigate this example and the workbench. Thanks again!

[franceecad]

Hi... I'm sorry but I'm not being able to get good results using this workbench... I read the documentation on Git hub but it is beyond my understanding.

Is there another doc to read or a more basic example to download?

Thank you in advance,

[qurn]

I had the same question, came across this thread and like to share a good solution i found on the way.

Here is a parametric globoid worm gear drive for OpenSCAD.
https://www.thingiverse.com/thing:2776688

It's nicely written. It explains the way to get geometry in the gif.
To import it in FreeCAD OpenSCAD Workbench paste the content of the 3 .scad files and adapt the parameters.

Pros: easy, fast, precise, good documented
Cons: won't be a native FreeCAD object.

[NormandC]

Another drawback is that it will produce a tessellated shape like a mesh.

[easyw-fc]

Importing an OpenScad file in FC will generate proper Features, not tessellated objects.
From the wiki:

FreeCAD will import the OpenSCAD-File and build up a tree with primitives and boolean operations

https://www.freecadweb.org/wiki/Import_OpenSCAD_code

[meme2704]

Hello
Here is a suitable approach often used in economic constructions:
a biconnic screw and a spur gear,
Can be improved by making a slightly inclined pinion parallel to the tangent to the screw