Inventor General Discussion

Inventor General Discussion

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Valued Contributor
pompeo79
Posts: 96
Registered: ‎02-08-2011
Message 1 of 9 (382 Views)
Accepted Solution

Positional Representation Assembly - Flippin' Problem

382 Views, 8 Replies
10-05-2012 07:42 AM

Hi,


i have  a problem to manage some pos representation  in this assembly )see link below).

 

The max vertical rep, (using angle constraint third type too) give me some problem with a cylinder and his rod, they just flip.

 

 

Any idea?

 

Thanks to all

 

To download the assembly:

 

http://dl.dropbox.com/u/63643836/Excavator%20Positional%20rep.rar

This is another example of Inventor's buggy constraint handling.

 

I've seen many flexible cylinders loosing their constraints and setting them bad, for no visible reason. This happens often with cylinder/rod combinations with +/- insert constraints. You can open the cylinder sub-assy, move the rod by mouse, and the constraint is back again.

 

With this excavator, all attempts with the cylinder near the boom were not successful. I only could get it stable, after moving it up into the main assy. Thus, I could get rid of the problems in Main and Free posrep, but not with Max vertical position.

 

This position simply can't be handled. The four bar linkage at the bucket assy flips and can't be set up, as needed.

As a remedy, I added Begrenzungswinkel and Begrenzungswinkel 2 as limits for the angular position of the bucket and the bucket link. But although the bucket angle was limited as +/- 30°, it's juming to about 105°. This should never happen, and results in flipping of the 4-bar linkage.

 

You can see this method working well in the minor assy Constraints ok.iam. But Inventor can't handle it in the still rather simple main assy.

 

I think, this should be improved. I don't need another UI change, but I'll have to do my job with tasks like that.

Walter

 

Files (only the changes) can be downloaded because of filesize for some time here:

www.holzwarth-cad.net/Joomla/media/download/Excavator_changes.zip

*Expert Elite*
harco
Posts: 879
Registered: ‎02-16-2006
Message 2 of 9 (374 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-05-2012 08:07 AM in reply to: pompeo79

I haven't opened your assembly so I'm not sure this answers your question but this is a common problem with hydraulic cylinders.

I assume you used axis/axis and angle constraints, I found this unstable.

If you have drawn the rod and the cylinder centred on their origins then use the origin workplanes to constrain the sliding.

This is a robust approach and should not flip.

Valued Contributor
pompeo79
Posts: 96
Registered: ‎02-08-2011
Message 3 of 9 (361 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-05-2012 01:25 PM in reply to: harco

I have tried already, the problematic cylinder....fixed in the orientation with the 3 origin plan, angle constraints.

 

Thanks for support!:smileyhappy:

 

Valued Mentor
Valued Mentor
wh
Posts: 502
Registered: ‎12-27-2003
Message 4 of 9 (338 Views)

Betreff: Positional Representation Assembly - Flippin' Problem

10-06-2012 04:02 AM in reply to: pompeo79

This is another example of Inventor's buggy constraint handling.

 

I've seen many flexible cylinders loosing their constraints and setting them bad, for no visible reason. This happens often with cylinder/rod combinations with +/- insert constraints. You can open the cylinder sub-assy, move the rod by mouse, and the constraint is back again.

 

With this excavator, all attempts with the cylinder near the boom were not successful. I only could get it stable, after moving it up into the main assy. Thus, I could get rid of the problems in Main and Free posrep, but not with Max vertical position.

 

This position simply can't be handled. The four bar linkage at the bucket assy flips and can't be set up, as needed.

As a remedy, I added Begrenzungswinkel and Begrenzungswinkel 2 as limits for the angular position of the bucket and the bucket link. But although the bucket angle was limited as +/- 30°, it's juming to about 105°. This should never happen, and results in flipping of the 4-bar linkage.

 

You can see this method working well in the minor assy Constraints ok.iam. But Inventor can't handle it in the still rather simple main assy.

 

I think, this should be improved. I don't need another UI change, but I'll have to do my job with tasks like that.

Walter

 

Files (only the changes) can be downloaded because of filesize for some time here:

www.holzwarth-cad.net/Joomla/media/download/Excavator_changes.zip

Valued Contributor
pompeo79
Posts: 96
Registered: ‎02-08-2011
Message 5 of 9 (331 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-06-2012 04:46 AM in reply to: pompeo79

Great reply Walter ! ! !    thank you ! !   :smileyhappy::smileywink:

 

That's the answer that i was wainting !

 

I have already downloaded your assembly, so you can drop off the rar,  thank you for your time and your patience to solve, change and upload !

 

At the end of the story just  a limit that need to be solved in Inventor Constraint with positional rep !

 

 

Valued Contributor
pompeo79
Posts: 96
Registered: ‎02-08-2011
Message 6 of 9 (327 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-06-2012 04:56 AM in reply to: pompeo79

Nice paper-style inv background :smileyvery-happy:

Distinguished Contributor
lkrenzler
Posts: 114
Registered: ‎09-09-2013
Message 7 of 9 (41 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-16-2014 09:13 AM in reply to: pompeo79

I see this was brought up years ago but the problem persists even in 2014.  Positional representations are a bit like I imagine hell to be.  Holy.

 

Inventor can't seem to tell the difference between -30deg and +30deg half the time for example.  Cylinders and other objects flip for no reason.

 

Angles are a huge issue in 2014 in general.  It seems Inventor just randomly decides to ignore clockwise or counterclockwise, depending on how it's feeling that hour.

 

This assembly for example worked perfectly for weeks, but not this morning.  Nothing changed but now the **** thing won't update by itself.  If I drag the cylinder manually it snaps back into position.  A similar assembly does not!  I had to change the angle setting to - and it works again (for now).  I run into this same nonsense every day.  I can count on the fact that any positional representations will at some point destroy themselves.

 

Another issue is that when I finally get it the way I want, Inventer often doesn't save the changes.  It says it does.  It saves.  But when I re-open it, the changes aren't saved at all.  This I run into constantly.

 

Does anyone know if any of this has been addressed in 2015?  Any improvements?  Just wondering.

 

 

Const.jpg

 

 

----------------------------------------------------------------------------------

Inventor 2014 Pro SP2 Update 2 - Win. 7 - Dell T-3500 - Quadro K2000.

NOT "Expert Elite" (as in relatively new Inventor user so double check anything I say)
Mentor
andrewiv
Posts: 635
Registered: ‎09-21-2006
Message 8 of 9 (30 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-16-2014 02:24 PM in reply to: lkrenzler

I used to have this problem as well.  Then they added a third option to the angle constraint dialog.  Now Inventor can distinquish between clockwise and counter clockwise.  I have not had these issues when using this option.

Inventor Professional 2014 SP2
Vault Professional 2014 SP1
Windows 7 64 bit
Distinguished Contributor
lkrenzler
Posts: 114
Registered: ‎09-09-2013
Message 9 of 9 (24 Views)

Re: Positional Representation Assembly - Flippin' Problem

10-16-2014 02:48 PM in reply to: andrewiv

OK, thanks, I'll give that a try.

----------------------------------------------------------------------------------

Inventor 2014 Pro SP2 Update 2 - Win. 7 - Dell T-3500 - Quadro K2000.

NOT "Expert Elite" (as in relatively new Inventor user so double check anything I say)
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