Flexibility not working properly in inventor - BUG that has been there for ever

[Cris-Ideas]

Hi,

I am trying to use flexibility feature but every time I give it a chance it fails me. There is a bug somewhere in inventor that makes it not capable of properly solving assemblies with flexible components.

This time I have run on to this issue with a very simple assembly, had been able to reproduce this buggy behaviour  tens of times, and had made video for you.

After unsuccessfully trying to post this I thought I will make another video for you so you could clearly see what is the difference when assembly is flat.

Here it is.

Here I have uploaded data set for you to play with :  http://a360.co/2fmTsvD

And in case you also think this is not working properly you can support idea to fix this: Fix flexible assemblies !

Cris.

[Cris-Ideas]

@johnsonshiue

Johnson, you did not follow the video and in fact did not try to reproduce the bad behaviour. Also you used data set from the begging of the thread and no the latest one.

What you present does not produce error in any case.

Can you please try to follow my workflow. I post another video with detail comment.

Cris.

[Cris-Ideas]

@karthur1

Hi,

have you tried to constrain the bolt in the same way as I did.

The idea of this example is not to place the bolt as it would be placed for the firs time but as it would be constrained for example when assembly is updated or changed.

Way of constraining this bolt is to show that inventor is not capable of solving this assembly when flexible bot is used once it is forced to flip the bolt to meet washer/plate constrain.

Swalton was able to reproduce it. in 2018 and 2019

Cris.

[karthur1]

---

@Cris-Ideas wrote:

@karthur1

Hi,

have you tried to constrain the bolt in the same way as I did.

The idea of this example is not to place the bolt as it would be placed for the firs time but as it would be constrained for example when assembly is updated or changed.

Way of constraining this bolt is to show that inventor is not capable of solving this assembly when flexible bot is used once it is forced to flip the bolt to meet washer/plate constrain.

Swalton was able to reproduce it. in 2018 and 2019

Cris.

---

Cris,

Yes, I applied the same constraints as you. I just noticed in my post #73, the link to my screencast is going to the wrong video.  Watch this video instead. 

It shows how I constrained your bolt assembly by using two constraints.  First with the axial constraint and then with the mate (flush).  When I edit the flush constraint to be on the opposite side, the axial mate will cause it to fail.

I then apply the same constraints to a non-flexible assembly and do NOT see the issue.  Seems to me that the problem is with the flexibility of the assembly and not how Inventor is solving the constraints.

I can reproduce what you are seeing in 2018.... but... if I use the single insert constraint I can edit it without issues.

I also tried what Johnson was saying about the new way 2019 allows the axis direction to be defined. It still fails in 2019 when the mate is edited and placed on a different face, even after I fixed the direction of the mate inside the flexible subassembly.  Here is a video of the error in 2019.

Kirk

[Cris-Ideas]

@karthur1

Thanks,

you clearly show this is failing even using constrains as Johnson suggests.

could you try similar example with bots you use?

@johnsonshiue

Kirk clearly presented the issue with 2018 and 2019.

Are you able to reproduce it in the same way?

Cris.

[karthur1]

Cris,

The mate constraint fails the same way using "my" flexible bolt assembly in 2019 as well.

If the assembly is non-flexible, the constraints will solve, but when it is made flexible, it fails.

Kirk

[johnsonshiue]

Hi Cris,

I am sorry this thread is getting very hard to follow. I have to review 60 threads (not counting new comments) on a daily basis. I may not follow what exactly you are looking for. I was hoping the new Axial Mate would help. It may not. Let me take a look and I will get back to you.

If possible, you may want to break up the thread into multiple new threads in the future.

Many thanks!

[Cris-Ideas]

@johnsonshiue

What I am looking for is:

Explanation how constrain solver works in case of flexible assemblies. Because obviously it works different than in case of the same set of constrains in case of flat or not flexible assembly.

&

I am also looking Autodesk finally admit constrains solver is not working correctly as it was shown many times in this thread alone. And in consequence start fixing it.

We are now almost two years in to this thread and during this time non of the above happen.

I know my data sets gets to development but I would like some feedback.

Is it really not possible for someone from development to participate here with some update from time to time?

Just lately 3 uses totally independently had confirmed the same bad behaviour of the constrain solver in 3 different versions of the software. Could we expect any comment on that particular case, witch by the way is very simple most basic example?

I mean comment other that "this was logged......"

Cris.

[johnsonshiue]

Hi Cris and Kirk,

I see your points. Indeed, if the Axial Mate is set to Undirected, the behavior remains unchanged. It is true that the original Axial Mate is Undirected. This is the main reason why we introduce Opposed and Aligned in 2019. By specifying the direction, Axial Mate will be more stable. The trouble with Undirected option is that user has no control over when it can be flipped or not, as shown in your videos. In some cases, it flips. In other cases, it leads to inconsistent constraints.

So, to see the correct or consistent behavior, you will need to use Opposed or Aligned. Please let me know if you still see issues with the two options.

Many thanks!

[Cris-Ideas]

@johnsonshiue

Yes it is still behaving the same way.

This error is always there.

It is not the problem with directed or undirected axial mate.

Problem is that inventor is not able to rotate the bolt in presented case.

I have been playing with this simple example for 5 hours. I have tried different ways of constraining both inside the flexible sub and top level assembly as well.

There are 2 very specific workflows that produce proper example, but non of them is possible to use in real life assemblies.

In any case all properly defined constrain sets should produce meaningful proper solution. If software is not capable of doing that than there is obvious problem in it.

To make your life with this thread easier I propose we meet on Zoom meeting and I could than directly present to you this and perhaps other examples.

What do you say?

Cris.

[johnsonshiue]

Hi Cris,

Sure! Please send me an email (johnson.shiue@autodesk.com) and we can get it scheduled at the time both friendly to you and me.

Many thanks!

[Cris-Ideas]

Two more videos and data set in the meantime

Please no advice how to solve without video. + I do know what triggers this bad behaviour, did it on purpose.

Point is that inventor acts in not acceptable manner. This is the problem here I am trying to point from the beginning.

data set available for download: https://autode.sk/2K0Zo8g

Cris

[Cris-Ideas]

I see almost no one likes this thread.

I had only got 5 likes in the entire thread. Am I not doing valuable job her?

Just kidding a little bit.

But seriously I would like to know what do you think.

Cris.

[Anonymous]

You have done a lot of research and work on presentations to show that it doesn't work all the time for sure! 

I have personally given up on flexibility and have figured work around's that do mess up my parts counts, but let me move things I need to move.

The theory of flexibility is awesome but I think it should just be removed until it works 100% of the time.

Albert

[Cris-Ideas]

Hi,

As proposed I have meet with Johnson on Zoom.

This was a productive talk, I believe.

During analysing some of the examples of the fails of constrain solver we have noticed that not all of them are directly related to using flexibility. That's sad news.

Below I post as short video presenting one of such situations. More to follow in new thread I started to discuss constrain solving issues not related to flexibility.

In the thread I will continue with the issues related to flexibility.

I encourage you to participate in the other thread as well. Constrain solving - as complicated as that

data set available for download: https://autode.sk/2M1tKwI

Cris.

[jletcher]

 @Cris-Ideas

 OK I looked at your flex bolt issue and here is our fix as promised.

Take a look at this video and see if this works for you.

[Cris-Ideas]

So far you have roved nothing.

If you look other videos with bolts constrained exactly like you did you will see hot they fail.

What you did was just a way to avoid initial error by making components flexible after they had been positioned.

This never brings up en error.

If you really want to prove something recreate exactly error producing workflow I present in the video and than upload it showing it works.

If you can recreate your example in AI 2017 and post it here I will make it fail.

As for the same way of constraining bolts there is already example of mine showing how this fails.

+ please comment on what you do in the video and what is the intent of the given action and how you can explain that.

Cris

[jletcher]

Your post is: Flexibility not working properly in inventor - BUG that has been there for ever

 I proved flex works and the workflow to make it happen, I did not know we were trying to make things fail.

I don't waste time making things fail, I make things work.

I would never make something Flexible without constraining the 1st constraint, it does not make sense to do that. Seems you are doomed to fail from the start doing this method.

So if this thread is about making things fail I don't have time for that,  if you want them to work I will help.

Let me know.

[Cris-Ideas]

Obviously you do not understand the issue here.

Thing is it fails not because I make it fail but because it just fails. I am able to reproduce situations that lead to fails and simplify the examples. So you are able to "make them work".

Great. Yo made work something that works. I want so things that do not work also was fixed.

So I do not mind you leaving this thread. If all work for you, I am happy.

Cris.

[jletcher]

Your workflow makes it fail so yes you make it fail.

 It is like trying to put a radius on a cutout in sheet metal but not have the cutout there yet.

Why would I want to turn on flexible before I need it?

  I am sorry but I guess I can't help you, you are making them fail from your workflow not because of an issue with Inventor.

 But if you need help making things work let me know I can help with that.

[Cris-Ideas]

Please do not writhe this nonsenses in this thread any more.

You are obviously not getting that this are examples simplified to the limit and all real life context is removed so to make debugging and understanding more easy.

My workflow is perfectly justified as I am not doing anything that software forbids. It is you workflow that makes this example work, but in real life this would be only temporary.

I understand you can't help me. No worries, will live with that.

Cris.