Sketch Lines resize and move illogically when adding constraints

[ryancrampton]

Why do lines resize and reorient erratically and illogically when adding constraints to sketches?  See the example below.  I want to simple constrain the floating line to have it's center point at the end of one of the other lines.  When I add a coincident constraint, the line I want to stay fixed is moved and resized and the line I want to move is held fixed.  It doesn't matter what order they are selected or any other choice I make.  There does not seem to be a logic behind which line moves and which line is fixed. 

If I add constraints to the line I want to stay fixed, the software continues to do weird things.  The line I want to move changes size or is rotated.  Why?  This is the worst method of sketching I've ever encountered in 20 years of working with CAD. 

There should be a basic logic to the process. 

1. The line that is selected second should always stay fixed.  Meaning I want to contrain point 1 to point 2, if I select them in that order, then I know which line will move and which will stay.  

2. The sketches should not be resized when they are moved.  I don't understand why at all this would happen.  What sensible logic is there to change the dimensions of the a sketch when it is constrained to another sketch?  It is random and stupid.

I can eventually add enough constraints to the first line to get the second line to move the way I want, but this is extremely inefficient and time consuming.  It's just a dumb, lazy programming method and I don't understand why.  It should be simple and quick to constrain two lines and have them stay the same dimensions and orientation, without first having to add a lot of dimensions and other constraints.  

[ryancrampton]

I posted the behavior in some pictures above in my original post.  I've currently moved on in my model and done what is needed to constrain the lines as I want.  So I do not wish to try and recreate this behavior for you.  It's certainly possible that in my time messing around with this, I duplicated a line or two.  

If you want to test it, just try drawing two independent lines in sketch.  Constrain one line to be coincident with the other.  When the lines are moved, they are also scaled.  It doesn't matter which order the lines are selected, Inventor moves the lines and scales them in an unpredictable manner.  

[dan_inv09]

Just because they remain movable does not mean that Inventor has to go out of its way to move them.

It should adjust the existing sketch as little as possible to accomplish the first (or any) constraint or dimension. Instead it seems to love moving (or stretching or shrinking or twisting) things that have nothing to do with what needs to move.

[CGBenner · Accepted solution]

@ryancrampton @dan_inv09 

I'm wondering if this is actually an enhancement request item.  I would encourage you, if you agree, to post this in the Inventor Ideas forum.

[ryancrampton]

Thank you.  I did not know that was an option.  I will put together a post for there.