Unstitch Bug.

[HughesTooling]

When designing a mould tool from a component you need a way to separate the inside from the outside. Sometimes you can use Offset Face set to zero to extract the required faces but I'm working on a small box with over 800 faces and chain selection doesn't work. There are only 8 faces joining the inside and outside so I thought I'd remove those leaving me with 2 shells. The trouble is after deleting or unstitching the 8 faces the 2 shells are still reported a a single body even though they're not touching, this seem wrong. A simple test, draw a cylinder change to the patch workspace and delete the cylindrical face and you'll be left with the 2 end caps as a single body! If you unstitch the 2 caps you can't restitch as they don't touch so surly having them show a single body after deleting the cylindrical face is invalid.

Edit. I did try unstitch then restitch on the 2 shells to see if that would separate them, it didn't go well. Here are the crash reports.

CER_148835999  CER_148831833

Mark

[paul.clauss]

Hi @HughesTooling

Thanks for posting! While I can see arguments for both sides of this issue (creating one or two bodies from the remaining surfaces), I have logged an improvement request (FUS-32914) with our development team, who will be looking into this workflow and considering potential improvements. 

I can see the option to maintain the disconnected surfaces as a single body for construction purposes - you may want to keep the relative positions of the remaining surfaces constant and using a single body is an easy way to do so. However, when working with more complex designs like your mold example, it would be a more efficient workflow to break into two bodies when the faces are deleted, as you would then not have to unstitch everything and then re-stitch the top and bottom surfaces respectively. As I am unsure of our development teams thoughts on this, I have logged the improvement request and will keep you updated on this thread with anything I hear from them.

I also had a look at your crash reports and it looks like you are crashing due to a known defect, ARRO-7836. This crash occurs after the Stitch command is used in a complex surface model. While it is marked by development as resolved, there are some comments on it mentioning that there have been many reports linking this defect in the last few days and the team will be looking into this behavior to investigate a possible regression.

Please let me know if you have any questions!

[todd_alford]

Hi @HughesTooling,

I wanted to elaborate to elaborate on Paul's response.  I dug into your cylinder example a little further to try to understand the bug and look for a workaround.

1st test was with chain select enabled selecting the annular face.

• Three bodies were created (as to be expected from a simple cylinder.

2nd test was with chain select disabled selecting the annular face.

• As you reported 2 bodies were created.

3rd test was with chain select disabled using a window selection to select all of the faces.

• Three bodies were again created

This is pointing me towards this being a selection issue more than it being an unstitch issue.  As you stated using the chain select doesn't work with your larger model.  Could you try doing something similar to my 3rd test with your complex part?  It should create 800 parts allowing you to delete the ones that you want and then stitch them back together using a similar process.  Can you let me know if that works?

Thanks,
Todd

[HughesTooling]

Hi Todd

I tried using unstitch to extract the 8 faces joining the inner and outer, hid the 8 faces then unstitched the 2 shells. When I tried to stitch all the faces after window selecting Fusion crashed, crash reports in the first post.

I have a few workarounds for this problem, in this case I ended up selecting all the outside faces and deleting them leaving just the core, offset surface with chain select worked for the outside. What's really needed is for boundary fill to work. I made a post here about the problem with boundary fill and came up with a workaround using extra planes, I forgot about this so I might have wasted some time when all I needed was an extra plane through the part.

Mark

[todd_alford]

Hi Mark,

As Paul said the development team is looking into it.  Also, thank you for providing the CER numbers with the additional information that is very helpful to us.  Could you provide me with your more complex file?  There is a functionality currently in development that I'd like to test with a more realistic part.

Also I'm glad you aren't completely out to dry without a workaround, I'm sorry you spent more time than necessary.  It might just be me, but I struggle using the boundary fill command at times.  I have used the "Fluid Volume" command setting the Volume to Internal.  The commands provide essentially the same output (my background is in computational fluid dynamics, so that one was the logical command when I started).  Might be worth taking a look at that as well, just to see if it fits your style any better.

Regards,

Todd

[HughesTooling]

I just tried the boundary fill workaround out using an extra plane so I'm given 4 cell to select from rather than 2 and it worked fine, I wont forget that workaround again.

Here's part of the core to give you an idea of what I'm working with. I'll ask my customer if it's OK to let you have the model, it might be a week or so as he's on holiday this week.

Mark

[HughesTooling]

I just tested boundary fill using just the component and 3 patches, no extra plane and it worked. Don't know if boundary fill has had some work done that fixed the problems I reported before.

Mark

[todd_alford]

Hey Mark,

I wouldn't be surprised, with Fusion there are constant updates as you know.  Sometimes the source of an issue is far away from where we think it is (which is why I started to suspect the issue had to do with selection).  So something that was wrong with Boundary Fill may have been fixed with an improvement to the Patch environment or something silly like that.  I may have been running into the same issue that you had with Boundary Fill, which is what brought me over to using "Fluid Volume" (again does the same thing creates another volume in or around your part).  I like the selection better.  No worries if you can't share the part either, more for personal interest in a couple of functions they are working on.  Let me know I'm glad you are up and running.  I'm sorry for the delay.

Regards,

Todd