Constrain solving - as complicated as that

[Cris-Ideas]

Hello All,

I have started this thread to bring up and hopefully explain problems related to constrain solver and gain knowledge on how exactly constrain solver handles the assembly.

This is because I am experiencing many problems related to assembly solving that should not be expected.

Originally I was discussing this issues in the thread related to problems with flexible assemblies but I decided to split this topics and this thread is intended to focus on constrain solver it self.

I would like to encourage especially people from Autodesk who have the knowledge about constrain solver it self to participate and help us understand better how this works to make our lives easier.

I will be posting videos and data sets, so anyone could try the same what I do and see if is getting the same outcome.

I also would like to ask you to do the same, and if possible use videos with comment rather than long posts, as this is more easy to follow and understand the intent.

I will be also giving each example a name, so it was easy to track replays. So when posting please make it obvious what you are referring to. 

If you are interested in problems related to flexible assemblies please visit this thread Flexibility not working properly in inventor - BUG that has been there for ever

Cris.

[Cris-Ideas]

How about hits super solve:

# 211 bug

https://autode.sk/2JsYRB9

Cris

[Cris-Ideas]

and another super solve

# 217 bug

https://autode.sk/2UblsX3

Cris.

[Cris-Ideas]

and another SUPER NONSENSE

# 218

https://autode.sk/2Yu8cfq

Cris

[Cris-Ideas]

And this

# 219

should you like to watch another video of this assembly please click here (it involves flexibility directly so I have placed it in the appropriate thread).

https://forums.autodesk.com/t5/inventor-forum/flexibility-not-working-properly-in-inventor-bug-that-...

Cris

[Cris-Ideas]

for anyone following this thread.

first video of 2020. (more to come).

Cris.

[Cris-Ideas]

# 234 bug - AI 2020

DOFs still not working.

Cris

[Cris-Ideas]

# 253 bug

simplest constrain update.

# 253 bug model

Cris

[Cris-Ideas]

#289 bug - inventor 2021 - simplest assemblies still not being solved properly

Hi,

It has been a while. But not thanks to bugs being solved in inventor, but because I was occupied with other stuff than working in inventor.

I have straggled for years and showed many, many times how bad is inventors' constrain solving. Many tomes we have heard "we are working on it", " this is fixed..."

But do not be fooled.....

Inventor still does not know where elements should be.

Basics are still not done, so nothing will really work 100% right

@johnsonshiue- why this is still here. You said before you have already fixed this at some point. Reintroducing bug again, as you did it the past?

Should anyone want to play with it here is a data set attached.

Cris.

Ideas-Creative Solutions

www.ideas-cs.com

[johnsonshiue]

Hi Cris,

Nice to see you again! Many thanks for sharing the example! If I understood this particular issue correctly, this is about the ability to drive the non-pattern-source component. I believe this is the designed behavior. A component pattern is largely driven by the pattern-source component as I explained before. If I misunderstood it, please show me the exact troublesome workflow, so I can follow up with the project team.

It is true Inventor is not perfect. It never will be. There are unresolved bugs and bugs to be found. I sincerely appreciate every issue you have reported. It keeps reminding us we are no where near perfect. We have got a lot of work to do. However, what troubles me is that you ignore the progress we made and keep claiming nothing works. I guess you have been doing perfect design using perfect tools. And, I am sorry that we simply fail to deliver.

Many thanks! Stay safe!

[Cris-Ideas]

Hi,

As I explained in detail (at least I tired) issue here is that:

1) pattern defined requires second component to be in certain position that is strictly defined as base component of the pattern is fully constrained and its position is fixed, so all components of the pattern that are placed by this pattern are (by definition) also fully constrained, so their positions are 100% defined and they have 0 DOFS.

2) in the same time it is possible (as demonstrated on the video) to drag second component of the pattern from the position that is defined by the pattern and place it somewhere else.  What is even more alarming is that it is possible to define constrains for the second pattern element that force this element out of the position that is defined by the pattern (also clearly shown and commented on the video).

So we have a situation where two constrain sets defined in a single assembly for a single element set require part to be in two different positions and inventor accepts this with no error message!. And we are not talking about using POS REPS here. Just a basic assembly.

And that is basically a problem here.

Conclusion is that: Pattern that should fully define positions of its elements (assuming base element is fully defined) does not do that!

hope this is clear.

As mentioned before. I have reported this ridiculous behaviour in the past and you have informed me that it is fixed at some point and I quote you wrote "second element is no longer draggable"

Johsnosn this are your exact words.

So another issue here is that this bug should have been fixed already, yet as shown it is still here in the software.

[johnsonshiue]

Hi Cris,

Many thanks for clarifying! I am sorry I was a bit confused and I did not quite get the issue. I think I get it now. It is indeed wrong. The second component pattern should not be able to alter the first component pattern's position. It does not make sense. It looks like there is DOF remaining unnecessarily. I will need to work with the project team to understand it better.

I also notice that if the first component in Comp Pattern1 is grounded or the rotational DOF is removed, the behavior will not happen. It shows that somehow the remaining DOF leads to this unstable behavior.

Thanks again!

[Cris-Ideas]

I am glad you understand the issue.

I have made some test and it turns out that there are flowing restrictions/constrains related to pattern that are working:

1) axial distance between this tubes is constant in any case, when dragged from the original position or constrained as shown on the video.

It turns out to be impossible to apply constrain that would require center distance of the tubes other than 70mm (value in this particular case)

2) XY origin planes of the tubes are always flush.

ps.

How do I turn on notification e-mails from the forum. It seems they are off again.

[johnsonshiue]

Hi Cris,

I am not sure if there was a change in preference. Go to your Autodesk account -> Site preferences -> Preference options -> check "Automatically subscribe me to topics or reviews I participate in."

Many thanks!

[Cris-Ideas]

@johnsonshiue  any feedback from project team?

[johnsonshiue]

Hi Cris,

Unfortunately, I have not got any reply yet. Let me ping the project team again. I am sorry for the delay.

Many thanks!

[Cris-Ideas]

While we wait for some feedback on #289 I have

# 291 to shear with you.

I would expect expression I enter to stay as I defined it rather than to be changed by Inventor, that obviously thinks it knows better what I had in mind.

Just to be perfectly clear here. Issue is that expression I enter is being changed in the way so result if not what it should be and everything is done without any notice or information that expression is being changed.

[Cris-Ideas]

Wonderful time of Christmas is coming and I have received, I would say a chrismations gift from the Constrain solver.

On the card it wrote:

"

Cris, you should now by now, I will solve the assembly, or I will not, depending on my liking, not your constrain set!
So do not try your tricks on me, it is I, the mighty CONSTRAIN SOLVER  that rules you design.

but if you find the right sequence of clicks I will make an exception and solve this assembly for you so you do not waist day or two.

"

So as you will find out in a minute (~8 minutes actually) constrain solver is still not capable of solving assemblies even with no flexible components and no components using POS REPS.

So here it is:

So all users-  give up hope for stable constrain solver, flexibility, and POS REPS.

Should you want to play:

https://www.dropbox.com/s/wm60cxkc7djg98e/%23%20293%20bug%20-%20model.zip?dl=0

Cris.

[Cris-Ideas]

another example of what we all know so well.

Result, sadly, as always.

model you can find in the original thread by @Anonymous

https://forums.autodesk.com/t5/inventor-forum/constraint-two-wheel-to-cross-a-random-path/m-p/9978813/highlight/false#M812578

Cris.