Joint Angular Limits

[mark.mmlj]

I keep loosing my angular limits in my assemblies.  I'll set them and have everything working the way I want then when I return to the assembly at a later date the limits are gone and I have to reset them.  I've resorted to creating notes attached to the joints with the limits recorded so I don't forget what I set them to...'cause I know they'll vanish and I'll have to reset them.  It just seems to be the angular limits that are effected.  Linear limits are OK and don't get lost.

What's the remedy?

[JDMather]

There are 3 types of Angle Constraints - which ones are you using?

[mark.mmlj]

If you select "Joint" on the Relationships panel of the Assemble tab, then you get the "Place Joint" dialogue box.  On the Limits tab of that dialogue box you'll see the Angular option.  You'll also get a similar dialogue that says "Edit Joint" with the same tabs if you choose edit an existing Joint.

[JDMather]

...make that 4 ways, including this method that I have never used.

[t_stramr]

Hi bud,

Can you attach some simplified assembly where the issue is easy reproducible? Also steps to reproduce the issue would be appreciate.

I will take a look what's wrong with joint angular limits.

Thanks for your post.

Robert

[mark.mmlj]

I made a simple assembly with the same kind of joints and angular limits I have been have trouble with, but I've never posted an assembly here.  Do I have to do anything special to the parts or assembly to post it here.

[t_stramr]

Nothing special is necessary. Just attach all IAM and IPT files that are necessary.

The best way is to ZIP all of them into single compressed file and attach this ZIP file. Its upt to you.

Robert

[mark.mmlj]

Here are the files.  This is a simple example.  The Pivot Mech.iam is the main assembly.  Under Representaions you should see several Cylinder joints, but two of the Cylinder Joints have Angular limits.  These are the types of limits that I keep loosing.  I don't know if it's because of a complicated set of movements that is the cause or what.  It seems neccessary to have at least to sets of limits or the movements spin wildy out of control.  I put some notes attached to the joints with the angular limits in case they disappear.

[t_stramr]

Hi Bud,

When I open your assembly in Autodesk Inventor Professional 2014 64-bit edition, I do not see any missing limits.

Look at next screenshots made when editing your joints.

Angular Start and End limits contain values that you put into your notes.

Could you make similar screen shots on your machine so I can see your result?

What is your version of Inventor where you are able to reproduce the issue?

Follow next pictures to find out Inventor version. Make screen shot as well so I can confirm that I test on the same builds.

Thanks,

Robert

[mark.mmlj]

I'm using Inventer Pro, 64 bit, Build 222, Release: 2014 SP1 - Date: Tue 09/17/2013

What I attached was a simple version of what I've been having trouble with.  It seems as though when I add more parts to the movement is when I loose the limits.  I recently lost the notes I had attached to my angular limits.  Don't know where they went.  You might try to add some parts to the assembly I attached and see what happens to the angular limits...whether they disappear or not.

[jonorutherford]

I'm having exactly the same problem. Was there any resolution?

[mark.mmlj]

No real solution that I've been able to find.  I've had some success adding all the parts first, creating the joint I need, then when everything is in place I set the limits.  Sometimes I've had to delete parts, close the assembly, then place the parts again and re-do all the joints and limits.  There doesn't seem to be any real rhyme or reason.  Sometimes it works and sometimes it give me fits.

[johnsonshiue]

Hi! I guess you are talking about the behavior that Rotational limit is violated during Drive or movement in large increment. This is a limitation unfortunately. The behavior is actually designed to help make the solving more smoothly. Otherwise, certain movement could be stopped in the middle. It does not happen all the time but it does happen when the solver detects the need. We have been investigating how to improve the behavior and make it better.

Thanks!

[jonorutherford]

Hi John,
Thanks for your reply. The problem actually occurs without the joint in
question being moved or driven. The assembly is a chain, and the links are
restrained to a movement of 30 degrees. As i put the limit on one link,
other limits on other links drop off! The limits also disappear if i try to
move the assembly. I hope this can help in your investigation into the
issue.

Cheers,

Jono

[JDMather]

I suspect you should only need one limit.

Can you attach the assembly here?

[jonorutherford]

Here is the part and assembly. Thanks in advance for your help!

[jonorutherford]

Not sure if my files attached last time, trying again . .

[JDMather]

Your attached assembly is missing parts (chain link is the only included part).

Sketch 1 in your part is not fully dimensioned and no clearance between pin and hole.

I suspect you might be trying to do too much with this chain, but without the missing parts.....

It appears to me that there would be interference between components - if the chain were anything but perfectly straight.

In the real assembly - what limits the degrees of rotation?

[jonorutherford]

Thanks again for getting back to me, sorry for the missing parts - I figured the issue was just with the link part. I've rebuilt the link with clearance between the moving parts and fully dimensioned the drawings (I think!) but am still having the same problem. In the actual part the movement is restricted by the interference between links, much as in the assembly.

Thanks again for your time!

Jono

[johnsonshiue]

Hi! Indeed, I think you seeing the behavior that Inventor removes angular limits in order to provide smoother solving behavior. Joint is supposed to provide more degree of freedom. During constraint solve, any component with enough of degree of freedom is allowed to move or rotate in order to satisfy the conditions. The limits may restrict certain legitimate solutions leading to choppy solve behavior.

In this particular case, I would suggest you use Contact Solver. The assembly does not have any interference, which is good for Contact Solver. Simply go to Tools tab -> Document Settings -> Modeling -> set Interactive Contact option to All Components. Then go to Inspect tab -> turn on Contact Solver. You will see the chain behave more like a real one.

Thanks!