topic Re: Allowing intersections? in Fusion Design, Validate & Document Forum

Allowing intersections?

makeable — Thu, 09 Feb 2023 10:59:53 GMT

I am trying to replicate the attached in fusion 360. It is a text stamp with a taper.

The method I have tried is:
- Import the text as an svg which becomes a sketch
- extrude the text with a taper

This fails because the taper intersects.

Is there some trick to doing something like this? It seems like it should be trivial, but the arbitrary restriction around the taper has me stymied.

Re: Allowing intersections?

TheCADWhisperer — Thu, 09 Feb 2023 11:14:00 GMT

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

Re: Allowing intersections?

makeable — Thu, 09 Feb 2023 11:19:49 GMT

I have attached, as well as a screenshot of the error i get in fusion.
Im not sure how much use to you the f3d is - it is effectively just a sketch.

Re: Allowing intersections?

makeable — Thu, 09 Feb 2023 11:22:39 GMT

FYI, I also tried a single profile at a time, but then i get problems with self intersection

Re: Allowing intersections?

TheCADWhisperer — Thu, 09 Feb 2023 12:17:17 GMT

Of course some real world logic based on geometry would have to make sense.

This is the shortest line in your sketch profile.

In the real world - what would happen after this converges to a point?

What if you removed that short line and instead had the angled line go to the horizontal line?

Extruding in the other direction results in a convergence to point here...

The root issue is that your input geometry is rubbish.

Notice that arcs are NOT arcs - all straight line segments. Even the lines are made up of unnecessary short segments.

In the last century we would call this the GIGO principle.

I would create the geometry natively in Fusion rather than importing rubbish into my design.

This geometry would not work in the real world and it will not work in Fusion (what happens in the real world after convergence to a point)?

Re: Allowing intersections?

makeable — Thu, 09 Feb 2023 12:46:38 GMT

Unfortunately, this is just a simple example - the shapes are predefined. As long as they are valid profiles, my expectation would be that it would intersect with other faces and for fusion to calculate the body accordingly. I get the same issue using complex native geometry.

Re: Allowing intersections?

TheCADWhisperer — Thu, 09 Feb 2023 12:48:03 GMT

@makeable wrote:
Unfortunately, this is just a simple example - the shapes are predefined..

You must have missed my point (pun intended).

The shapes profiles are made up of multiple tiny lines.

Can you show what happens in the real world geometry after convergence to a point?

Take care of this issue and the problem is solved.

Re: Allowing intersections?

makeable — Thu, 09 Feb 2023 13:22:26 GMT

Thanks for your help. I understand your point about the garbage geometry. Unfortunately in this case I have no control over the sketch, other than ensuring it is a valid profile - it would simply be far too much work to recreate the geometry. Even then there would still be problems where there are small details.

I guess fusions not a good for for this particular task, so ill just have to keep my old workflow for that.

Anyway - thanks for your input! Its always appreciated 🙂

Re: Allowing intersections?

makeable — Thu, 09 Feb 2023 15:02:20 GMT

FYI, I have attached a screenshot of how onshape handles this - as im sure this is a limitation of fusion, rather than a limitation of CAD in general. It allows the faces to intersect, creating new bodies, which i then union. Ive also attached the exported mesh so you can see how it removes any hidden geometry (not that its much use as a mesh). I am able to work with it as if it were any regular solid.

Re: Allowing intersections?

TheCADWhisperer — Fri, 10 Feb 2023 13:06:57 GMT

@makeable wrote:
- as im sure this is a limitation of fusion, rather than a limitation of CAD in general.

@makeable

Your mesh geometry does not match the geometry you are attempting to Extrude - this is different geometry.

You could duplicate this geometry in Fusion but it would be a lot of work.

Re: Allowing intersections?

makeable — Fri, 10 Feb 2023 16:56:36 GMT

The geometry should be the same?

To be sure, I have attached the DXF that i used in onshape. I couldnt use the SVG as onshape doesnt support SVG.

I just tried again with the DXF in fusion and I get exactly the same issue I did with the SVG.

Re: Allowing intersections?

makeable — Fri, 10 Feb 2023 17:00:53 GMT

I tried in shapr3d (based off parasolid) and that also works with the same DXF.

Its entirely possible that I am doing something silly in fusion, I just cant seem to replicate this behaviour that is supported in 2 other popular CAD packages.

Re: Allowing intersections?

makeable — Fri, 10 Feb 2023 17:45:03 GMT

I drew an "e" as a sketch in fusion, same problem. Its definitely not to do with the SVG/DXF - fusion simply cant handle self-intersection (at least thats is how it appears to me).

Re: Allowing intersections?

makeable — Fri, 10 Feb 2023 17:47:41 GMT

Yet it works for 2 concentric circles...

Re: Allowing intersections?

makeable — Fri, 10 Feb 2023 17:49:45 GMT

And squares. Note how the faces intersect. No issue with those lines converging to a point