Contraint problems with flexible assemblies.

[shastu]

If constraints are fine in an assembly.  Why would they become corrupt when used in another assembly.  See constraints video.  I open the file and see constraint errors.  I open the assembly and there is nothing wrong with the constraints.  I edit one of them and just bring up the dialog box and click on O.K.  Then all four of them are fine until I go back to the assembly they are used in and update that assembly.

Then look at the constraints_0001 video.  As you can see I have all the degrees of freedom that I need because I can drag the assembly in all six directions yet when I try to insert it where I want it, I get errors.  Very FRUSTRATING!

Find videos at the following FTP site:

ftp://ftp.bradburyco.com/

Username: Customer

Password:  Bco462

There will be a zip file in the Download to Customer\Autodesk folder

[johnsonshiue]

Hi! Without seeing the actual files, it is very hard to tell where the problem is. But, based the video, I do see the red cross lit up. I assume there are failed constraints in the assembly. Indeed, Inventor allows users to keep modeling with failed constraints. Solver tries its best to come up with mathematically correct solutions. However, the solve behavior could be unpredictable or unintuitive in this state.

Could you send the files to me so I can take a look?

Thanks!

[shastu]

The red cross is irrelavent in this case.  Even if I start without the red cross I get the same results.  I remembered after posting this that I have run into this before and it has to do with constraining to parts that are component patterned within the assembly.

[shastu]

I had one of the wrong videos in that zip file.  I updated it.  You can see in the second video that the red cross fades out after updating the constraint and then comes back for no reason.  Is there any plans to get this to work more user friendly?

[johnsonshiue]

Hi! I fully understand the frustration when undesirable behaviors occur without any further information. However, without seeing the actual files, it is extremely difficult to find out where the problem is.

Thanks!

[shastu]

Fair enough,  I have put the files on the same FTP folder.  Everything is fine (no RED cross) until you unsurpress Insert 10.  Please let me know when you have the files downloaded so that I can take them back off the FTP site. 18006-12T.iam

Thanks,

Shawn

[johnsonshiue]

Shawn,

I cannot seem to find the file. Where did you put it? I don't see it under \Autodesk\

Thanks!

[shastu]

I am not sure shy you wouldn't be seeing it.  It is under the Autodesk Folder.  Can you please check again?

[johnsonshiue]

Shawn,

I got the file now. Please unshare it. Somehow I had to reboot in order to see the file. Anyway, I will get back to you as soon as I find anything.

Thanks!

[johnsonshiue]

Shawn,

I looked at the assembly you sent me. I wish I could reply to you earlier but this is not an easy problem to understand. I confirm that the constraint of interest fails to solve in a reasonable manner. But, I am not certain where the exact problem is at this point. I will need to forward it to development for review.

I do find a few places I would do differently, however. There are quite a few places in the subassemblies where constraints are being applied to component pattern occurrences instead of the pattern source. This practice might look benign when you added the constraints in the beginning. But, it could introduce constraint conflict down the road when these components need to be moved or rotate to satisfy other constraints added later. The reason why there could be conflict is that Comp Pattern is like a special constraint applied to the occurrences. Let's say you have PartA and you make it a pattern of two instances in X direction. You will get PartA:1 (source) and PartA:2 (occurrence). There is an imlpicit constraint between PartA:1 and PartA:2 to ensure PartA:2 always stay a distance from PartA:1 in the selected direction. Now, if you apply additional constraints to PartA:2, it is possible PartA:2 will have to be moved freely based on the constraints. However, its existance and definition solely depends on the implicit pattern constraint between PartA:2 and PartA:1. If somehow a constraint requires PartA:2 to move or rotate in a manner violating the pattern definition, the constraint will fail to solve.

Based on how Comp Pattern works in Inventor, I would suggest the following changes to the assembly.

1. Avoid constraining to pattern occurrences if possible.

2. Restructure components by demoting to reduce degree of freedom.

3. In one subassembly (two-level deep), somehow a non-Master PosRep is active, while other components are in Master state. This is adding to confusion.

In the mean time I am forwarding the issue to development. Thanks!

Johnson

[shastu]

Attached is another video showing the problem.  If I make the assembly flexible before I constrain it, then it causes all kinds of failures.  If I constrain it first and then make it flexible, it doesn't cause any failures.  That absolutely seems impossible.  File is on the same FTP site as listed above.  It is called flexible_nonsense.