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Unexpected reversal of draft feature normal vector (draft direction)

tbraxton
21-Topaz I

Unexpected reversal of draft feature normal vector (draft direction)

I have multiple models with draft features where the draft direction will reverse unexpectedly when making modifications to the model. What is odd is that the modifications are not made to the draft feature so no change would be expected unless modifying a parent reference of the draft (not usually the case). Creo does not provide any notice that the normal vector has changed and the model fully regenerates successfully.

 

These models are complex geometry with many surface and usually some ISDX features in them. I would like to find a method to have Creo flag features where this is happening. Currently the only method I have to catch this is to do a tedious and manual draft analysis check of the whole model.

 

I suspect the issue is that upstream surface geometry is experiencing a flip of the surface normal and this is somehow triggering the change to the draft feature. This is speculation on my part but based on observations of changes seen of directions for trim and merge features flipping direction on regen when working with the models. These flips of the surface normal most often cause regen failure and are corrected but the drafts will sometimes regenerate with either normal direction and regen incorrectly but remain unnoticed. 

 

If anyone has any insight to this or has experienced the same scenario I am interested to learn about it. I am trying to generate a detailed query  to submit to PTC for investigation. Ideally I would be able to get a relatively simple model where this behavior can be triggered on demand.

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Involute Development, LLC
Consulting Engineers
Specialists in Creo Parametric
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