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Author Topic: 3D DXF output  (Read 222 times)
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wjh30
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« on: March 27, 2020, 12:32:18 PM »

Both Solidwork s 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 manipulat e in my favorite 3D CAD package.
The helical gears I am generatin g are far too complex for Solidwork s 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 appropria te helical angle? Is it that simple?
It would REALLY be nice if the 3D DXF export worked as it should.
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ArtF
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« Reply #1 on: March 28, 2020, 06:55:46 AM »

 

  Its true, the 3d dxf's can be hard to import in some software and its mostly a case
of loose definitio n. 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 unstandar d.

   For helicals, you can rotate the base image, it has been predistor ted so that a simple
rotationa l spin extrusion will work.

Art
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wjh30
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« Reply #2 on: March 28, 2020, 11:23:57 AM »

Thank you Art, today I will learn how to do that in both Solidwork s and Fusion.
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wjh30
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« Reply #3 on: March 28, 2020, 12:40:05 PM »

I am an airline pilot by professio n, 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 magnitude s too much.
Ok... I did a 3d Sketch, came up with 12.094757 08 degrees.
« Last Edit: March 28, 2020, 01:17:43 PM by wjh30 » Logged
ArtF
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« Reply #4 on: March 28, 2020, 04:43:21 PM »

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 circumfer ance
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;
  RadiansTo Twist = .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;
  RadiansTo Twist = .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



  
  
« Last Edit: March 28, 2020, 04:47:43 PM by ArtF » Logged
wjh30
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« Reply #5 on: March 28, 2020, 06:03:22 PM »

Thank you Art, my gears are currently printing from my method and will try them out(they are Lego Technic compatibl e). 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?
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ArtF
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« Reply #6 on: March 28, 2020, 07:58:56 PM »

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
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