3D DXF output

[wjh30]

Both Solidworks 2019 and Fusion 360 show a corrupted gear. When playing with the demo, and reading the manual, it suggested that I could export a 3D solid I could further manipulate in my favorite 3D CAD package.
The helical gears I am generating are far too complex for Solidworks to convert into a solid body. Best I can do is a surface body which isn't what I want.
Suppose the only thing I can do with the helicals is import the 2d DXF and do a swept extrude at the appropriate helical angle? Is it that simple?
It would REALLY be nice if the 3D DXF export worked as it should.

[ArtF]

 

  Its true, the 3d dxf's can be hard to import in some software and its mostly a case
of loose definition. DXF is probably one of the worst file formats in that way. In some
software your better off with the STL file when trying to convert to a solid, but even there
the standards are pretty unstandard.

  For helicals, you can rotate the base image, it has been predistorted so that a simple
rotational spin extrusion will work.

Art

[wjh30]

Thank you Art, today I will learn how to do that in both Solidworks and Fusion.

[wjh30]

I am an airline pilot by profession, not an engineer, when I specify the amount of twist in the extrusion, for a 45 deg helix gear, what formula do I use? Obviously 45 degrees for twist is a few magnitudes too much.
Ok... I did a 3d Sketch, came up with 12.09475708 degrees.

[ArtF]

Hi:

  The helical angle defines the angle of a gears face. So the angle you'd use would
depend on the facewidth of the gear. In other word show much "twist" one would use
is defined by Tan(45) * width = twist. That "twist" would be a circumferance
rotation of the other side to get  to 45 degrees from the starting gears potion.

 If you divide this twist by the gears radius, you have the radians of rotation.

Ex: .5" thick 45 degree gear. 4" diameter

 twist = Tan(45) * .5"
 twist = .5;
 RadiansToTwist = .5 / 4" = .125 = 7.16 degrees of rotation of the back side of the gear.

Ex: .25" thick 35 degree gear. 6" diameter

 twist = Tan(35) * .25"
 twist = .17505;
 RadiansToTwist = .17505 / 6" = .0291 = 1.67 degrees of rotation of the back side of the gear.


 Let me know if this leads to any questions.

Note:  The gears radius above is the pitch radius, not the outside radius..

Art



 
 

[wjh30]

Thank you Art, my gears are currently printing from my method and will try them out(they are Lego Technic compatible). I MUCH prefer your way, thank you very much for the formula.
One more question Art, can I make a custom axle for Gearotic? Namely for the Lego technic shafts?

[ArtF]

Hi:

You can, but its not intuitive. You need to import the dxf of the gear or
import it directly to Vexx. Draw the new shaft profile and remove the old
one, group the gear and select extrude.
 
Art