I've seen one instance myself just yesterday of some bad
parametic processing on Inventor's part. I had modeled a
fairly simple part with the base extrusion going in one
direction. Later in the feature tree I added a linear hole
on one face of the main extrusion (no sketch). Then I thought,
in order to have the origin plane centered on the part's main
extrusion, maybe I should edit the base extrusion to be a
midplane extrusion. Problem is, when I edited that feature,
I got an error message that my holes features had no effect
on the model. So, I tried editing them to see what was up, and
the preview showed the hole placement now going in opposite
directions both ways, and as far as I remember, you are not
allowed to enter "negative" values for these placement
dims, so the easiest fix for me was to undo the midplane feature
edit and live with it the way it was. Inventor SHOULD have been
able to keep those placement dims for the holes without flipping their
directions to make the hole off the part!
Bob
Dennis Jeffrey wrote:
> 1. iMap maps constraints - does not indicate feature dependency.
>
> 2. Most if not all 3D parametric modelers have feature dependency.
> Avoiding dependency requires rethinking your workflow. This is not
> something "fixable" in the current sense.
>
> If you create a feature that is based upon an existing feature
> (including work features), then that newly created feature cannot be
> moved above the dependent feature. See the attached 2009 part.
>
> Assembly features such as a hole are dependent upon a sketch. That
> sketch location is dependent upon selection of a face within the
> assembly. Therefore, the sketch and the whole are dependent upon that
> face being present within the assembly. If that face is deleted or
> moved, then the sketch, and the hole feature have no home, forcing
> redefining of the sketch. It all depends on what level of the assembly
> that you're placing the hole feature. If you placed it at the top level,
> then it will only exist at the top level.
>
> --
> Dennis Jeffrey, Autodesk Inventor Certified Expert
> Autodesk Manufacturing Implementation Certified Expert.
> Instructor/Author/Sr. App Engr.
> AIP 2008 SP2, AIP 2009-SP1 PcCillin AV
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> http://teknigroup.com