Bug report - 3d cosmetic thread visual versus 2d drawing

[b.ognjenovic]

Haven't check if this one was already reported or not.

When using the "move face" feature and the face contains a "Hole feature" with cosmetic thread visually shown, then in the 3D model the cosmetic thread is streched together with the face. So by looking at the 3D model, all looks fine.

When creating the 2D drawing, the costmetic thread length has not grown in the same amount as the 3D model did, basically resulting in a incorrect 2D drawing thread depth.

Although the "move face" feature is absolute not the way to draw such geometry, the draftsman was tricked anyway, because the 3D model appears correct.

Suggestion: either the hole feature  and it's costmetic threads should not be affected by a "move face" command. Alternatively if they should be affected, then the 2D drawing needs to be corrected so that it reflects the actual 3D model appearance.

[CGBenner]

@johnsonshiue 

Just wanted to bring this one to your attention.

@b.ognjenovic 

Welcome to the forum!  Can you share what version of Inventor you see this in?

[SBix26]

The quickest way to fix this is to move the hole feature in the feature tree to after the Move Face features.  That way it is calculated from the new location instead of the old one.  It may not be possible because of other dependencies, but that's what I would try first.

If you're able to post the part here, I'll take a look at other methods to deal with it.

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Sam B

Inventor Pro 2023.1.1 | Windows 10 Home 21H2

[b.ognjenovic]

The version I am using is 2021.4.2.

Thanks for all the replies. It is not relevant for me to fix the issue as it is already resolved.

Preventing this from happening again is what I'm aiming at. The mismatch between what is visually shown in 3D versus 2D (in the scenario when a draftsman used the Move Face feature) and the procured parts that follow with mistakes in them. This part was copy-designed and then modified to fit a different assembly and, this is the reason why the move face feature was used. Normally this feature is not used for designing such parts. The file is attached.

[SBix26]

I have no knowledge of the details of how Inventor stores such information, but my suspicion is this: that the 3D model representation and the 2D drawing view representation have essentially nothing to do with each other. 

The 3D texture is applied to the appropriate face, but cannot extend past the face, so it only shows as far as the face goes.  The 2D view is calculated from the model data, and is therefore "correct" as far as the model history goes.  The thread depth is calculated from the face as it exists at that point in the model history and is not recalculated farther down in the tree.  While it would be nice for Inventor to alert us to the potential problem in such a case, I don't think this could be called a bug-- pretty sure this is working as intended.

You'll notice that the same thing applies to any feature that references a face that is later moved by Direct Edit.  It is calculated per conditions as they were at its location in the model tree history, and is not recalculated later in the tree.  The problem in this instance is that the 3D model cannot display the discrepancy.  I would liken it to the problem of male and female cosmetic threads looking as if they match in diameter, when in fact they are two different sizes, simply due to the female cosmetic thread displaying (by default) as the minor diameter.  Hard to detect in the 3D model, but important to look for.

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Sam B

Inventor Pro 2023.1.1 | Windows 10 Home 21H2

[johnsonshiue]

Hi Folks,

If I understand how it works correctly, this is considered a limitation. When you moved the faces after the Hole/Thread was created, the Hole was not aware of the change. As a result, the spec remains the same. It is better to make such geometric change before drilling the holes.

Many thanks!

[b.ognjenovic]

Perhaps it is not a bug indead or just a limitation, I'm not sure. But as long as the 3D representation does not match the 2D then I consider the move face feature as a liability and will advise the other engineers to avoid this feature when using hole features.

Thanks for your inputs.

[IgorMir]

Hi Johnson,

Yes, it looks like a limitation. But it can bring some confusion to a less savvy operator. Since the cosmetic thread does follow the moved face.
Looking a bit further into it - even if we use "To" option in Hole DB and after that - Thicken or Extrude that terminating face - the thread doesn't follow in the drawing view. Yet - it is shown correctly in the modeling window. That, on its own - can be classified as a bug, I believe.
Here are two files in IV2020 format, which demonstrate the issue. In there I have three options - Thicken, Extrude, Move. Suppressing/Un-suppressing them allows to see - how the drawing view is behaving.
Cheers,

Igor.

[johnsonshiue · Accepted solution]

Hi Folks,

I am sorry I did not articulate the limitation properly here. The issue is that the thread texture follows the geometric change but the actual thread spec (which the drawing follows) is not updated accordingly.

Inventor isn't capable of refactoring such change. This is why I mentioned earlier it is better to alter the geometry before creating the Hole/Thread features.

At the moment, I am not aware of a straight forward solution allowing it to work desirably.

Many thanks!

[IgorMir]

Hi Johnson,

You have explained it all well in your original post. The thing is - the cosmetic thread feature shouldn't follow the moved geometry. Since that change is not documented in the drawing view. But it is not the case. And that's not right.

I realize - that behavior will never get changed. Inventor users just should be aware of such a limitation with cosmetic threads. That's all.

Cheers,

Igor.