Trouble with a 3D Sketch Reversing Direction with Parameter Changes

[petestrycharske]

All,

Good afternoon!  I've run into a somewhat strange situation where a 3D sketch seems to be reversing one of the directions when I make some changes to the parameter table.  The issue only shows up when making larger changes and only when the parameters increase in size.  Very strange and I welcome any advice.  Please see the screencast below and I've attached a copy of the part file as well.  Thanks in advance for any assistance, hope all is well and have a most blessed day!

Peace,

Pete

[johnsonshiue · Accepted solution]

Hi Pete,

This is indeed an interesting behavior. I believe it has something to do with how 3D Sketch is solved. In 3D Sketch, Inventor is using the same solver for solving assembly constraint. The flipping behavior is that the solution is indeed mathematically valid but it does not make sense for the design intent.

I am able to delete a dimension and add d19 between the 3D line and the moving workplane. The result is more stable. Could you take a look at the attached part?

Many thanks!

[petestrycharske]

Johnson,

Good afternoon!  My apologies for the delay in getting back to you, but thank you so much for the response!  I tested out your version of my part and it does perform MUCH better.  I mostly understand what you are saying, but am still confused that the model doesn't respect the orientation of the workplane for certain combinations of values.  However, that being said, I can certainly use your approach and accomplishes the goal just as well.  I'll keep that methodology the next time I run into a scenario like that.  Appreciate the help and have a most blessed day!

Peace,

Pete

[johnsonshiue]

Hi Pete,

The behavior is indeed confusing. But, from constraint solving's perspective, as long as the two lines are kept at the given distance, it is a valid solution. There isn't a constraint limiting the direction of the offset.

Many thanks!