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tmchenry
Posts: 70
Registered: ‎02-14-2011
Message 1 of 12 (288 Views)

Mystery Frozen Assemblies

288 Views, 11 Replies
02-18-2013 03:59 PM

I'm a relatively recent convert to Inventor (background in SolidWorks, SolidEdge, and Solid Designer).  Been using Inventor for two years, but I continue to be vexed by a problem with some of my company's legacy assemblies that I have never been able to figure out.  I'm hoping someone here can shed light on the issue.

 

Every now and then I open an assembly that appears to be a normal assembly in every way, but it is not possible to move any components in the assembly.  Typically, there are no broken constraints, but often there are components out of place from where the constraints indicate they should be.  It's not possible to move any components, even by deleting all existing constraints and replacing them with new constraints. None of the immovable components is grounded.  (Although a previous engineer here, who created many of these assemblies, had a nasty habit of building assemblies by just grounding components in place, rather than constraining them.)

 

Is there some feature for "freezing" an assembly that I'm not aware of and, if so, how do I "unfreeze" them?  So far, the only way I've been able to make these assemblies usable is to rename the file and then create a new assembly from scratch, saving it to the original filename.  Obviously not a very good long-term solution!

 

Tedd

*Expert Elite*
CelticDesignServices
Posts: 507
Registered: ‎11-29-2011
Message 2 of 12 (286 Views)

Re: Mystery Frozen Assemblies

02-18-2013 04:12 PM in reply to: tmchenry

tmchenry wrote:

I'm a relatively recent convert to Inventor (background in SolidWorks, SolidEdge, and Solid Designer).


So I take it your background is pretty "solid" then...Sorry, someone had to say it.

Welcome to the Inventor side of things.

 

I hate to say it but without having your assembly to look at and dive into, I can only throw darts and hope I get something right.

 

You eliminated the "grounded" question (I've seen my share of users building assemblies that way...ugh).

Are the assemblies using a Position Representation or even a Level of Detail?

 

The only other thing that comes to mind is sometimes constraints are tied to other constraints and are "frozen" in that sense until the other constraint changes or is deleted. I've seen that happen rather often.

 

You said you have to delete the part and then reinsert and constrain it? Just for giggles, have you just deleted all the constraints in the assy and attempted to move the parts then?

 

Can you maybe post a small assmebly that you are having these issues on? I'm sure someone here can access it and find out what the deal is.

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Valued Contributor
tmchenry
Posts: 70
Registered: ‎02-14-2011
Message 3 of 12 (280 Views)

Re: Mystery Frozen Assemblies

02-18-2013 04:24 PM in reply to: CelticDesignServices

I made a pack-n-go of the latest example I've encountered, but the zipped version is still 7.7 MB.  Do you think that's too big to upload?

 

Tedd

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sbixler
Posts: 1,845
Registered: ‎09-15-2003
Message 4 of 12 (278 Views)

Re: Mystery Frozen Assemblies

02-18-2013 04:29 PM in reply to: tmchenry

Yep.  I believe the file size limit here is 1.5 MB.  If you have time and patience, you could try opening the biggest part files and dragging the End of Part marker to the top of the tree, hiding all geometry, then save.  This reduces file size by a considerable amount, and you might be able to squeeze in under the limit.  Or save it somewhere else (the AUGI website is one possibility) and post a link to it.

Sam B
Inventor 2012 Certified Professional

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Valued Contributor
tmchenry
Posts: 70
Registered: ‎02-14-2011
Message 5 of 12 (272 Views)

Re: Mystery Frozen Assemblies

02-18-2013 04:43 PM in reply to: sbixler

Hm.  I tried simplifying the assembly by deleting some parts.  Once I got it simple enough (three parts), it started to behave normally.  I.e., if I suppressed mates I could move parts.  So I think maybe the issue is constraints somehow tied to other constraints, as Jim suggested.  I'm going to poke around with it a bit to see if I can figure out what's happening.

 

If I find out anything interesting I'll post the results.

 

Thanks,

 

Tedd

Employee
t_stramr
Posts: 49
Registered: ‎08-15-2011
Message 6 of 12 (217 Views)

Re: Mystery Frozen Assemblies

03-12-2013 04:04 AM in reply to: tmchenry

Tedd,

 

The best way to see whether your component is able to move is to check its degrees of freedom(DOF). You can show/hide DOFs for all components in the assembly by menu "View->Degrees of Freedom", or for individual components by context menu on component node in the browser view where you choose item "iProperties...->Tab: Occurrence->CheckBox: Degrees of Freedom".

 

Robert

Valued Mentor
mpatchus
Posts: 437
Registered: ‎10-22-2008
Message 7 of 12 (211 Views)

Re: Mystery Frozen Assemblies

03-12-2013 04:13 AM in reply to: tmchenry

One thing to keep in mind, often folks will constrain parts using a skeleton model which is an acceptable workflow.

However, constraining individual parts to LINES or POINTS in a sketch can result in more than one possible solution.

That is why we always utilize PLANES in our skeleton models.

Mike Patchus

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LT.Rusty
Posts: 632
Registered: ‎10-23-2012
Message 8 of 12 (185 Views)

Re: Mystery Frozen Assemblies

03-12-2013 11:12 AM in reply to: mpatchus

I wonder if the parts were created using in-place modeling techniques?  If so, it's entirely possible that there's geometry projected between parts.  If this is the case, then you can't move anything because the projected sketch references are holding things in place.  If the parts are moved, the sketches break, so Inventor doesn't allow the parts to move.

 

Check for this, see if parts / sketches / etc are adaptive in your assemblies and sub-parts.


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Valued Contributor
tmchenry
Posts: 70
Registered: ‎02-14-2011
Message 9 of 12 (176 Views)

Re: Mystery Frozen Assemblies

03-12-2013 11:27 AM in reply to: tmchenry

"I wonder if the parts were created using in-place modeling techniques?"

 

That's a good thought, I'll check for that next time I find an assembly with the problem.

 

One of the issues here is that when the company decided to switch to Inventor (from AutoCAD) it cheaped out on the training.  Not only did the engineers not have any experience with Inventor, they didn't have any 3D CAD experience at all, but I think they only got one day of training.  (This all happened before I joined.)  So there is legacy of early CAD models that have problems, made during the early years when they were learning things the hard way.  The cost of those legacy models is orders of magnitude greater than a little extra training up front would have cost.  A great case study in how not to make a paradigm change in your engineering processes!

Employee
Posts: 1,631
Registered: ‎04-30-2008
Message 10 of 12 (164 Views)

Re: Mystery Frozen Assemblies

03-12-2013 01:18 PM in reply to: tmchenry

Hi! The behavior you describe does not sound right to me. Please send it to me at johnson.shiue@autodesk.com so I can take a look.

Thanks!



Johnson Shiue (johnson.shiue@autodesk.com)
Principal SQA Engineer, Inventor
Mechanical Design
Autodesk, Inc.

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