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Nested adjustable assemblies and constraint errors.

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beachcomber

Mechanical
Jan 19, 2005
1,488
I have an assembly that contains several adjustable assemblies (hydraulic cylinders and shafts with UJ's).
I now want to place this assembly into a higher level assembly and make either make it adjustable or drive the sub-assembly positions via the peer-variables command.When I do this it's OK for a couple of changes, then I start getting conflicting and failed constraints.
Has anyone else done nested adjustable assemblies, and if so do you have any similar experiences, or can you provide some guidance on what should/should not be done.
Our version is V17.09 and we are also seeing other errors with constraints - in assemblies and in parts.
Sometimes a profile in a part will show as not fully constrained even though it obviously is (especially hole circles), and new parts placed into an asembly are showing as fully positioned when there is only one mating condition applied.

bc
 
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Hi beachcomber,

For adjustable sub-asm, the thing is that, once you make it adjustable, it makes all the internal relationships available (what I mean by internal is assembly relationships for the parts inside the sub-asm). It also transfer the sub-asm relationships to the appropriate internal part (you can delete and rebuild those relationships if it helps). What you have to do is add asm relationships to internal parts directly (not through the sub-asm anymore).

NB: I've noticed that if the adjustable asm is the first component in an asm, you can often expect weird behaviour.

For your problem of profile, I don't know. Couldn't it be just a display problem ?

For your problem of parts fully constrained too fast. Check with updates. I think it's a known problem and I believe it was fixed at some point. (doesn't happen in V18 in any case).

HTH,

Fred
 
Thanks Fred,
I think I follow what you mean.
I think I have sorted it since I posted the question.
To summarise :
Top-level assy 'A'
Level 1 assy 'B'
level 2 assy 'C'
In assy B we make C adjustable, everything works ok.
In assy A we attach assy B.
Now, in assembly A pathfinder we drill down the assembly structure to find C and make it adjustable. This will also make it's parent assembly B adustable. Assembly B is then toggled back to rigid.
We can now use the peer variables command to drive assembly B to different positions.
Alternatively we can leave B adjustable and drive it within A only.
Hope this makes sense

As for the profiles, it's mainly hole circles - sometimes it seems like they are not being recognised, but if we delete them and then put the in again everything is ok.
I've seen the part constraint problem in a previous version of SE, and that was corrected with a new serice pack.
bc
 
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