Draft analysis - Plastic Part Design

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saso
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Re: Draft analysis - Plastic Part Design

Post by saso »

Surface analysis tools are indeed common in all cad programs, most common and basic are curvature, zebra and draft. FreeCAD has the zebra analysis and also sort of the curvature in the Mesh Design WB (I say sort of because it works only on mashes that one has to create manually, while normally this tools work also directly on surfaces). I am guessing that curvature and draft analysis actually work in a similar way in all cad systems, so maybe the existing curvature analysis could be adopted/updated to be able to do also the draft analysis and that they would work also directly on surfaces/solids (maybe some sort of in the background fast on the fly meshing)... ?

The fact that FreeCAD is missing this and that it would be nice to have it is however known for a long time, but as others have said, nothing happens by itself, someone with the needed knowledge and interest will have to take the time to do it :)
Last edited by saso on Wed Jan 18, 2023 7:36 pm, edited 3 times in total.
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onekk
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Re: Draft analysis - Plastic Part Design

Post by onekk »

saso wrote: Tue Jan 17, 2023 5:32 pm ... FreeCAD has the zebra analysis and also sort of the curvature in the mesh design wb (I say sort of because it works only on mashes that one has to create manually, while normally this tools work also directly on surfaces).
..

In the Curve WB if I don't remeber wrong there is a Zebra tool.

See as example:

https://forum.freecadweb.org/viewtopic.php?f=3&t=63911

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saso
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Re: Draft analysis - Plastic Part Design

Post by saso »

onekk wrote: Tue Jan 17, 2023 6:11 pm In the Curve WB if I don't remeber wrong there is a Zebra tool.
Yes, zebra is in Curves WB...

... here is "not the best" workaround for draft analysis using lights from Arch Texture WB (visually it is sort of ok, but the user does not really have the needed precise control over the angles that is needed for real draft analysis) :?

draft with lights.gif
draft with lights.gif (786.59 KiB) Viewed 1407 times
Last edited by saso on Wed Jan 18, 2023 7:37 pm, edited 3 times in total.
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onekk
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Re: Draft analysis - Plastic Part Design

Post by onekk »

saso wrote: Tue Jan 17, 2023 6:28 pm
yes, zebra is in curves wb...

... here is "not the best" workaround for draft analysis using lights from arch texture wb :?
...

The point that probably is missing is what is creating the texture, probably is something related to coin3D so some mesh passage is involved (Coin3D is reusing the tesselation that OCCT returns as a graphic representation of the solid), so probably what you are seeing is not the "real mathematical surface", but an aprossimated representation.

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Re: Draft analysis - Plastic Part Design

Post by saso »

onekk wrote: Tue Jan 17, 2023 6:50 pm The point that probably is missing is what is creating the texture, probably is something related to coin3D so some mesh passage is involved (Coin3D is reusing the tesselation that OCCT returns as a graphic representation of the solid), so probably what you are seeing is not the "real mathematical surface", but an aprossimated representation.
Yes I am guessing that for this type of analysis a mesh is used also in other cad tools (for example, they often have the option how precise the analysis should be, which is also typical for meshes), but I am guessing that they do the meshing in the background (the user does not actually see the generated mesh) when the user analyses a solid/surface.

The first thing to check would IMO be to see if there is existing support also for draft analysis in the code that is behind the curvature plot from Mesh Design WB (it has already support for abs, mean, gauss, min, max curvature, change it in property -> view -> display mode) or if it could be possible to somehow add it to it, also thickness analysis (MeshLab library http://www.vcglib.net/ for example has the shape diameter function for this, so maybe it would be interesting to check how/if draft analysis is possible to do in MeshLab https://www.meshlab.net/) and possible other similar analysis...

IMO it would be a good step forward even if at first this additional analysis would work only on manually generated mashes as the current curvature plot.
Last edited by saso on Wed Jan 18, 2023 7:37 pm, edited 5 times in total.
Ferdi
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Re: Draft analysis - Plastic Part Design

Post by Ferdi »

Hi! Yes, "Draft Analysis" would be a great tool to have!
A very bad, non FreeCAD workaround, would be the "3D-printing Toolbox" in blender. Turning the model downside in the draft direction, you can search for angles above a certain value.
draft_blender.jpg
draft_blender.jpg (75.07 KiB) Viewed 1285 times
If anybody knows a free tool for Draft Analysis, let me know!
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Re: Draft analysis - Plastic Part Design

Post by GeneFC »

Alexander Egistov wrote: Tue Jan 17, 2023 4:47 pm 3. Why doesn't the team who makes FreeCAD writes such fundamental things for FreeCAD?
Go back and read what I said.

This is a minority usage of FreeCAD. A pure guess, but I would expect a very small percentage of users have any interest. This is by no means fundamental.

That sort of function only happens when an interested coder gets busy. Could happen tomorrow or never.

Gene
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Re: Draft analysis - Plastic Part Design

Post by saso »

saso wrote: Tue Jan 17, 2023 7:14 pm ... so maybe it would be interesting to check how/if draft analysis is possible to do in MeshLab
Just a little test of the idea using MeshLab, filters -> range map -> select faces by view angle, on a very coarse mesh... :roll:

Animation.gif
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Alexander Egistov
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Re: Draft analysis - Plastic Part Design

Post by Alexander Egistov »

GeneFC wrote: Wed Jan 18, 2023 12:18 am
Alexander Egistov wrote: Tue Jan 17, 2023 4:47 pm 3. Why doesn't the team who makes FreeCAD writes such fundamental things for FreeCAD?
Go back and read what I said.

This is a minority usage of FreeCAD. A pure guess, but I would expect a very small percentage of users have any interest. This is by no means fundamental.

That sort of function only happens when an interested coder gets busy. Could happen tomorrow or never.

Gene

Sure buddy - draft analisis of molds is not fundamental, that's why almost every CAD package has it, because a LOT of people design molds.
But you're right - without such a feature it IS minority usage of FreeCAD, just like only a minority of people would attempt to use a hammer to screw in a bolt.
Alexander Egistov
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Re: Draft analysis - Plastic Part Design

Post by Alexander Egistov »

saso wrote: Wed Jan 18, 2023 12:47 am
saso wrote: Tue Jan 17, 2023 7:14 pm ... so maybe it would be interesting to check how/if draft analysis is possible to do in MeshLab
Just a little test of the idea using MeshLab, filters -> range map -> select faces by view angle, on a very coarse mesh... :roll:


Animation.gif
A quick thought - many slicing softwares can show you which angles on the part will need support, meaning of the value of the wall's angle is above or below a certain range, it will highlight it, and if I am not mistaken Cura and PrusaSlicer which can do that are opensource.

One workaround option would be to export the part, slice it in the right orientation and to see draft/support angles, another one would be to integrate that into freecad.
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