Spiral Bevel Gear solid model creation.

[Ken_Shea]

Just to make sure I am not over looking something.

Is it possible to create a solid model of these gears?


Thanks
Ken

[ArtF]

Ken:

Yes, you can create stl files of almost anything GM makes. BUT, its models of bevels are bad. There is a workaround though to get good ones. Download the latest dev. version of the software. A new Icon called Gearotic Thoughts will be added to your desktop.

Create a bevel with GM , save the project, run GearoticThoughts, load the project with the Import button. A proper and fixed bevel will load. Right click it in the tree and "Save as STL" will appear. It will save as a binary stl as I havent put a user switch for ascii yet.
The printed examples you may have seen in previous posts were from GT, after saving a project in GM.

  Future version as GT expands will allow for adding splineshaft holes, or square shaft holes as well as keyways,likely within a couple weeks.

  Let me know if you have any trouble..

Art

[Ken_Shea]

You can't really work/model with .STL's Art, their not a solid, surface or geometry just a zillion little triangles  ;D

Thanks

Ken

[ArtF]

Ken:

:), tell me about it, they not only are a zillion triangles, but the rules say no triangle can share a face with any more than 1 other triangle..real learning curve to create them well. But to get a solid model requires all them triangles for most software..
  What kind of 3d model are you looking for? There ARE many types..but so far Ive only been using stl's as my main output
for models. Actually, I think you can consider an STL to be a geometry as well as a solid model..or even a surface..its just one
representation of all of those..many more are possible of course..


Art

[Ken_Shea]

Art,
I am not sure what CAD uses them for really, haven't figured their use out from my limited experience.
Seems most CAD can import them but at least with in OneCNC you can't do much with them to alter them or convert them to a Solid. I guess they could be considered geometry but don't believe they use arcs.
OneCNC does not consider them a Solid, not that that means anything particularly.
Common solid and/or surfaces formats are  .Stp/.IGS/.Sldprt/.3dm .stp and .igs being the most universally used.
Am modeling a 90 degree gear box, found one gear but not a RH and LH so they don't mesh but that does not matter in this case, only a model.

Thanks Art

[ArtF]

Ken:

  Ahh, I think I get what your saying...

    STL, .Step, .etc are all really the same thing, just with the information given differently. An STL for example CAN represent curves,
or functions. They can be nonsolid, or solids. All of them are used by CNC toolpath algorithms to determine a shape form which to
make a solid object depending on the method used to build it. Never used OneCNC, but from what I understand it should be as able to
generate Gcode pathing from an STL as a .step or igres. They all simply tell the program what the end shape your looking for is.
  Now as far as converting them to a solid, thats a bit unclear as to meaning. They are a solid by definition. In fact , if you look inside an STL, the file format
checks that the first word is "Solid" in order to check its an stl. OneCNC may have a different definition of "Solid", Id guess there are several
ways to define it. A .step file for example isnt a solid either. Instead of triangles, its a list of "steps" one woudl take to build something.
Basically a list of faces ( which can be triangles , quads or contours) and a list of things to do with them. ( Thats a very general description ).
  So in terms of a cad output, .step makes as much sense as anything else. But the end model, wether stl or .step or whatever shoudl be able
to be used to generate toolpaths or whatever one needs to do. STL's are pretty standard that way, look to Vectric Cut3d and such programs
and its what they expect in order to machine a solid from a shape.

  Much of this is really a matter of what a specific program wants to see as its input or what it wants to put out for output, no one format is actually any better or
worse per say..just different depending on the application..

Art

 

[Ken_Shea]

Art,
OneCNC is a Nurbs modeler and that's as far as I can go with what that may mean  :D

Even that one little .stl gear really taxes the CPU with the zillion entities having to be calculated when rotating etc, it is also has a 40mb file size, any other file format would be a fraction of that. An example is a very similar gear with a .igs format file that is 1/10 that size and even less when saved in OneCNC .xfa file format.

.STL may be what's needed for 3D printing though and a little reading on .stl tonight seems to indicate that is exactly what it was designed for.

Glad it's you doing GM and GT, I'd gave up long ago and no one would have had GM and GT would not have been so much as a dream.

Ken

[JustinO]

Triangles! I'm still working on understanding these dang "line segments".

[Ken_Shea]

JustinO

This is a line ____
This is a Triangle ▲

;D ;D

[ArtF]

Ken:

  Size of file doesnt mean much. STL's for example can be binary or ascii format. Ascii makes them 10 sizes
larger. Binary is almost like a zipped form.
  In the end, its all about data and how you describe it to a computer. Generally the more data you need, the more
complex the item. Take a cube, easy to describe as its 6 sides all the same. As you can imagine, describing a bevel gear
is much more complex, with a million faces, each normal to a specific plane.... no matter what language you use (format)
describing it to a blind man to make is going to be tough. ( And thats basically what all these formats are, a way to decribe
to a blind man ( Your computer) how to make an object..

  Nurbs is common with some software too, A nurbs program try's to reduce the complexity of an object by describing it
with formula's. BUT, if a shape is too complex the number of formula's can increase to a level where the complexity
makes more data than even an STL.
 

Art

[Ken_Shea]

Way beyond my understanding Art.

Is it a possibility for gear out put to be added for  .iges or .stp ? at some point?
If not I understand.

Shouldn't take long, only took a few seconds to ask  ;D

Thanks
Ken

[ArtF]

Ken:

It may happen. Trouble is that Step or iges are very complex formats having more to do with process
than with objects. I do have it listed ot invstigate it more, but it looks to be a very expensive proposition to
attempt to add such a thing. There are however, free convertors for stl2Step if you doa  google for that.

  Probably best for now to attempt to convert your stl's to iges or step via pu8blic software. Mileage will vary.
A typical conversion of a 8meg stl file can generate about 150megs of step file, so its not a trivial data conversion.

Art

[Ken_Shea]

Hi Art,
I did see one of the conversion programs last night, think it was Meshlab or like that.
Works but as you mention makes huge files and not with out model cvompramises.

OK then, I won't hold my breath  ;D

On another note, can a GM gear train, say just two spur gears be out put as a single .2D dxf?
Haven't found a way to select both if it is possible.
Can load them individually into CAD but then the center to center measurements and gear mesh does not seem to work out with out some repositioning.

Thanks
Ken

[ArtF]

Ken:

  At the moment at least you cannot. One of the reasons for all these types os limitations is due to the
reasoning of usage. Take the step file.. its great for when one wants to modify a part. It describes operations
really that allow you to modify a part beyond its design criteria. But, since there are really no modifications
that should be done to something like a gear, it doesnt make a whole lot of sense to have it partitioned that way.
    I will grant that some woudl like to do things like modify spokes and such, and its commonly done by simply
importing the dxf, a 3d model is a lot harder to modify for anything like spokes and such.
  A 2d dxf that includes 2 gears I can see, it at least cuts down on having to copy and place another gear properly
to center. ( But if you do load a second dxf and place it at the right center diatance they will mesh, but you may have to
rotate one of them on its center to make that happen. ). If you load a second dxf and place it inline with the first gear
it will mesh, but if its at and angle to that first gear youd have to rotate it by the angualr amount to get a mesh. Its
how GM causes everything to mesh. BUT, even if I were to put 2 gears in a dxf, youd find you cant move one without
its mesh becoming just as bad as if you loaded two separately and placed one in the wrong spot.

  All of the above are reasons that its hard to use any CAD program to do gearing on, it can be done but its difficult
because the programs usually dont keep track of the important meshing variables to control how they draw. 

    As  I develop the new GUI, I will look at additional output formats and ways to ease import to other programs,
but with the variety and proprietary nature of many of these "standards" its a hard road to pave.

Siemens owns most of the code for these thing,s , even SolidWorks is really a siemens based program as all the parasolids are
made by siemens Code. ( Im an ex Siemens employee and I know how that stuff is to emulate...)

  I will do my best to make sure I give as much power as I can that makes sense for this type of problem though..

Art


 

[Ken_Shea]

Hi Art,
I understand that this is mostly beyond the scope of GM but not knowing what the suggestion would entail thought I'd ask.

If it works out to add additional file formats that would be great and believe it would enhance GM, if it doesn't then I understand why now.

Thanks
Ken