Constraint Identification Issues

[f_calebh]

There's a couple different levels to this particular question, so a little background:

A user contacted me with a complex sketch that they couldn't fully constrain. They were missing 1 constraint and no degrees of freedom were shown. 

Truthfully, this issues seems to happen quite often. I trace it back to users not having a complete understanding on the best practices for using geometric constraints in their sketches. A lot of times they'll default to auto-constrain to finish what they can't identify. One thing I've noticed is that sometimes auto-constrain will actually over-constrain a sketch without the software realizing it. As a user dives deeper into the sketch the whole thing becomes completely un-stable. A user can end up deleting a dimension and the sketch it will erupt into a mess of sick pink dimensions. It's at that point one can see that there are some conflicting constraints causing issues. 

So first I want to ask; is sketch stability a known issue and is there work being done to fix how Inventor identifies over-constraining a sketch and showing appropriate degrees of freedom? If not, I'll make a point to find some more examples as they come to me where sketch constraint's and over-constraints aren't being properly identified and attach them to this message string.

Anyway, to the main point of this thread. I was in the process of fixing one of these over-constrained/missing constraint sketches when I ran into something peculiar. When I found the and removed the offending constraints and replaced them with appropriate constraints, my color highlights on constrained geometry didn't seem to be working anymore.  A fully constrained sketch was showing lines and radii that weren't showing in my constrained color scheme.

It's a complex sketch so I removed bunch of the excess features and objects to show a cleaner view of the issue in the video.  I've attached the file along with a screen cast of the issue. *note the sketch was turned into a block so you'll need to edit the block to get to it.

Is there any way to fix this with out redrawing the objects that are having issues? There's quite a few of them in the original sketch. I can remove every single constraint and dimension but the line never corrects it's appearance.

[imajar · Accepted solution]

I cant answer your first points, but in the file you attached the line you are having trouble with has a color override applied.  If you right click the line, and click properties, you will see the line color is set to black.  Just change that back to default and the color will obey the constrained/unconstrained color scheme again.

For the rest of the sketch you can group select everything and change the color back to default.

[johnsonshiue]

Hi! Many thanks for sharing the files! I took a look at the part. I think this is a bug. The issue here is that when the sketch block was created, the projected origin point was included. But, when the sketch block is edited, the origin point isn't shown. The behavior is wrong.

To avoid the behavior, when you try creating a sketch block, please do not include the projected origin point. Then it will work correctly. In the meantime, I will work with the project team to understand the behavior better and correct the issue accordingly. It has been reported as INVGEN-47047.

Thanks again!

[f_calebh]

@imajarReally? Wow, thanks for the catch! I thought I was going nuts.. Of course the color scheme I use shows unconstrained lines as 'black' 😐

[f_calebh]

OK, thanks, I didn't think projected geometry was supposed transfer over. I usually try to have users apply a fixed constraint instead of constraining to the origin if the sketch is going to be used in a block. Force of habit usually causes people to forget that.

I think the biggest issue I had with this sketch was finding the right constraints since it appeared the user had changed some of the line colors. I'll accept that solution since that was the main issue I was having on this sketch. I'll start a new post if a user sends me any sketches that reference the over-constrained issues I thought might have been related.