Extrusion Tool extrudes in wrong direction, shown correct in preview and wrong after extrusion

[Anonymous]

As you can se in the pictures below, Fusion changes the direction it extrudes in after confirming. It's the last extrusion in the attached file. A workaround i found is to change the direction so it's wrong in the preview and right after.

[TrippyLighting]

While this is likely a bug, my recommendation would be NOT to use any 3D sketches for this. Just not needed!

[Rushikesh.kadam]

@Anonymous Thank you for reporting this. I have created a ticket and assigned it to the concerned team.

Once again, appreciate your effort in developing the software.

Also, as mentioned by @TrippyLighting my recommendation is also not to use a 3D sketch for this.

---------------------------------------------------------------------------------------------------------------------------

If my reply was helpful, please click the "Accept as Solution" button. This helps others get the answer more quickly! "Like" is always welcomed.

[jm.10]

I'm also experiencing this exact bug. Screen recording is attached.

- The preview of the extrusion is in the correct direction

- After clicking OK the extrusion reverses itself

Also note that I am not using 3D sketches. This affects normal sketches just the same.

The fact this is still happening over 4 years after being reported and acknowledged is insane. Autodesk should be ashamed of this garbage.

[TheCADWhisperer]

@jm.10 

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

[jm.10]

So I created a "minimal" demo file that shows the problem. Just try to extrude the bottom profiles together as shown in the screenshot and note the preview is correct but the resulting geometry is wrong.

With a bit of experimentation I can also reliably reproduce this with other geometry. The bug seems to be triggered when extruding multiple profiles together that have opposite normals. In this case, the outer "shell" is the bottom face of the part with a -Z normal, while the inner profile is sketched on a construction plane whose normal points in the +Z direction.

This obviously should not be a problem, as evidenced by the fact that the preview handles it perfectly fine. The geometry kernel itself is perfectly capable of handling the geometry. The bug is some sort of logic bug in Fusion that causes it to change how it interprets the geometry depending on where the geometry is being computed. I strongly suspect that similar bugs are also responsible for some of the unexplainable "broken geometry" problems where a part's geometry suddenly changes in unpredictable ways just by closing and reopening the part. It really proves just how fragile and unreliable Fusion is.

[TheCADWhisperer]

@jm.10 

Can you Attach the file after completing the Extrusion?

[jm.10]

File after extruding the lower profiles in the -Z direction. The resulting "extrusion" instead applies in the +Z direction.

[TheCADWhisperer]

@jm.10 

OK, now I see the issue and can reproduce the unexpected behavior.

[T_J_OBriensWeldX]

Rushikesh your "recommendation" is rude and disrespectful. Every time someone on these discussions does something in a way that isn't like all the old people do they are told "just don't do that" and given no clear instruction on how they should or an overly complicated way to do it.

Using a 3d modeling program in 3D should not be discouraged.

[T_J_OBriensWeldX]

Same issue here. always spending more time trying to work around bugs or "old ways" of doing things instead of just modeling. I just wish that SolidWorks wasn't so computationally intensive so that I could use it on my laptop.

[TheCADWhisperer]

---

@T_J_OBriensWeldX wrote:

Using a 3d modeling program in 3D should not be discouraged.

---

@T_J_OBriensWeldX 

3D sketching as used by many beginners is use incorrectly. True for ANY CAD software.

If you have a specific question, you should ask it here, someone will show you how to use the 3D sketching correctly when appropriate or how it is not needed/appropriate in a particular case.

[TheCADWhisperer]

---

@T_J_OBriensWeldX wrote:

I just wish that SolidWorks.... 

---

@T_J_OBriensWeldX 

Computationally efficient techniques are identical in all CAD softwares.

There is a lot more functionality in mature softwares, but basic techniques are largely identical.

Let's communicate with actual geometry.

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

[TrippyLighting]

---

@T_J_OBriensWeldX wrote:

... I just wish that SolidWorks wasn't so computationally intensive so that I could use it on my laptop.

---

Do you have any first-hand experience with that?

At work, I run SolidWorks and Fusion on a 6-year-old Dell Precision Laptop. Both work just fine.

The sketch engine in SolidWorks is much more mature. It is faster and more stable than Fusion's sketch engine.

The parasolid kernel is also faster in many operations than the ACIS-based Autodesk Shape Manager.

Both are licenses from Siemens

[TrippyLighting]

---

@T_J_OBriensWeldX wrote:

Rushikesh your "recommendation" is rude and disrespectful. Every time someone on these discussions does something in a way that isn't like all the old people do they are told "just don't do that" and given no clear instruction on how they should or an overly complicated way to do it.

Using a 3d modeling program in 3D should not be discouraged.

---

At some point, the folks at Autodesk decided to create a single sketch engine that unifies 2D and 3D sketching. I have submitted hundreds of bug reports since I started using Fusion in 2014. The current state is that, while the sketch engine is vastly improved from even 5 years ago, the 2D portion still has many bugs and some limitations not present in more mature software. For example, you still cannot define tangency between a spline and another sketch object. There are still cases where the sketch engine cannot accurately determine if a sketch is fully defined in 2D.

The 3D part of the sketch engine is not fully developed and fully functional, so that a sketch can be fully defined.

That is why we are recommending working with 2D sketches. 

Also, clearly, a bug was recognized and recorded. So if a user wishes to complete their work, a workaround or alternative workflow must be provided, at least until the bug is removed.

Hence, the recommendation was not rude or disrespectful!