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Can't move unconstrained parts within an assembly

55 REPLIES 55
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Message 1 of 56
ben_walker5
46382 Views, 55 Replies

Can't move unconstrained parts within an assembly

Hi, I have been building an assembly and suddenly I am unable to move parts according to their constraints. I can move them as soon as they are placed but as soon as I add one constraint it's as if they are glued in place. For example, when I line up two holes I can no longer rotate one part around the grounded component.

 

Have a turned off some functionality of the program?

 

Any help would be much appreciated!

 

Ben

55 REPLIES 55
Message 2 of 56
KF090
in reply to: ben_walker5

I'm having this same problem, hopefully there is an easy quick fix.

Message 3 of 56
SBix26
in reply to: KF090

There should be quite a few threads in this forum over the last several years that discuss this problem.  Unfortunately there is no quick fix-- it seems that Inventor can get confused in certain assemblies, and there is no solution other than deleting a bunch of constraints and starting over.  But do some searching and see if there's any more guidance from people with the benefit of experience.

Message 4 of 56
blair
in reply to: ben_walker5

Look for a bad constraint, this seems to freeze parts, also having a second part selected in the browser will do the same thing as well.


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
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Delta Tau Chi ΔΤΧ

Message 5 of 56

do as the others have suggested, but just to get you out of trouble if it needs to go out the door...

 

Although you can not drag the component, you may be able to move it by adding additional constraints, just add them as you would normally would and see if it moves correctly

Stephen Gibson



View stephen gibson's profile on LinkedIn


Message 6 of 56
t_stramr
in reply to: ben_walker5

Hi Ben,

 

Could you attach your assembly? If you have some simple assembly that exhibits the problem I can take a look closer for source of the problem.

 

Thank you,

Robert

Message 7 of 56
rjezuit
in reply to: t_stramr

I have had this issue also, in 2010, 2011, and 2012.  It seems to be related to previously placed parts that are grounded. If I "un ground" parts placed before the one that is messed up it seems to free them up. Then I ground the previously un grounded parts. 

Message 8 of 56
Barvas11
in reply to: ben_walker5

I have the same problem. And as rjezuit says, try to ungound your parts. Every assembly should have only one part grounded no more than that. Another thing that could be causing this are adaptive sketches and parts. You should always turn the adaptivity off. 

Message 9 of 56
JDMather
in reply to: Barvas11


@Barvas11 wrote:
.... Every assembly should have only one part grounded no more than that.
...

I often have multiple grounded components (parts or sub-assemblies) within my assemblies.


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Message 10 of 56
Barvas11
in reply to: JDMather

Well that's what we were told by Autodesk employees. I must say that it makes my life much easier because assemblies with high number of grounded parts don't tent to behave as they should.... 

Message 11 of 56
rjezuit
in reply to: Barvas11

Sometimes it is necessary to have more than one grounded part, but it is preferable to use the constraints to hold things where you want them.
Message 12 of 56
JDMather
in reply to: Barvas11


@Barvas11 wrote:

...makes my life much easier because assemblies with high number of grounded parts don't tend to behave as they should.... 


Fortunately I have never experienced any adverse behavior with any number of grounded parts.


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Message 13 of 56
douthett
in reply to: ben_walker5

First thing you need to do is run Rebuild All.  This should either fix the problem or show you which constraints are bad.  You then have to fix ALL the bad constraints.  Once you did that, rerun Rebuild All, with luck no more bad constraints will appear.

 

This typcially fixes the problem.

Message 14 of 56
blair
in reply to: rjezuit

If you are IV2014, there is a icon that will show sick constraints in the modeler window.


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
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Delta Tau Chi ΔΤΧ

Message 15 of 56
LT.Rusty
in reply to: rjezuit


@rjezuit wrote:
Sometimes it is necessary to have more than one grounded part, but it is preferable to use the constraints to hold things where you want them.

No, it's really not.

Constraints eat up a lot of memory and processor cycles.  Grounded parts don't.

 

Once a part is situated, unless it's going to be moving ... ground it and delete the constraints.  It'll make a difference in your performance.

 


@Barvas11 wrote:

Well that's what we were told by Autodesk employees. I must say that it makes my life much easier because assemblies with high number of grounded parts don't tent to behave as they should....


Odd, the Autodesk employees I've talked to have said much different.

Rusty

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Message 16 of 56
douthett
in reply to: LT.Rusty

That would be a freaking nightmare if you ever had to change the shape on a part.  You would have to go into your assembly unground everything that if affected by the change, constrained it, ground it again and then remove the constraint.

 

The company I work for has huge assemblies and we use constraints

Message 17 of 56
LT.Rusty
in reply to: rjezuit

Well obviously you can't do it everywhere, but there's plenty of places where it's a very good thing to ground things rather than constrain them, particularly when you've got assemblies that are simply not going to change.  When something's still under development, still not finalized ... then yeah, you don't want to do that.

Rusty

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Message 18 of 56
rjezuit
in reply to: LT.Rusty

For the most part we are engineers. When doassemblies not change? I tend to like contraining things as they will really be assembled, with constraints, not grounded. 

Message 19 of 56
JDMather
in reply to: rjezuit


@rjezuit wrote:

.... When do assemblies not change?


 

If I am doing a sub-assembly pushed out from a multi-body master file, the part size/positions changes are defined in the master file.
The point is there are times when grounding (how about Frame Generator) is perfectly OK and makes logical sense.

 


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Message 20 of 56
rjezuit
in reply to: JDMather

Do you use the demote function to build your subs? Then the parts have the constraints from the master. As far as frame generator, I do not use it so I cannot speak to that point.

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