3d-sketch tangent issues

[TobiasZetterberg2067]

Why is the tangent constraint working so horribly in 3D-sketching?

I have been poking around with the tangent command for some time now without getting it to work.

I draw a line and an arc which I then try to make tangent with the "tangent constraint" which applies and show the right symbol but the line and arc are not even close to beeing tangent.

Is this some sort of bug or what?

/Regards T

[Cadmanto]

My guess would be that they have two different X, Y, Z coordinates.  If they are not on the same plane, the tangent wont work.

If this solved your issue please mark this posting "Accept as Solution".

Or if you like something that was said and it was helpful, Kudos are appreciated. Thanks!!!! 

     

[SBix26]

Can you post the file?  I've used tangent successfully in 3D sketches, and I'm curious how this one is failing without reporting an error.

What version of Inventor?

Sam B

Inventor Professional 2018.2.3
Windows 7 SP1

[TobiasZetterberg2067]

Hi!

No, there is only one coordinate system.

I have attached a part-file with an example of a straight line and a arc that have "coincident contraint" applied but are not tangent.

Im running AIP 2018, build 112, Release 2018.0.2, 64-bit.

/Regards T

[jeremy_wasserstrass]

Are your arcs co-planar?

[TobiasZetterberg2067]

There is only one arc in the posted file and it doesnt matter if I put the line and the arc on the same plane, still not tangent.

/Regards T

[SBix26 · Accepted solution]

I can't explain what's going on here.  I played around with it, constrained the two lines, added another line on the end of the arc, still couldn't get the tangent to solve-- until I dimensioned the radius of the arc.  Then suddenly both tangencies jumped into place (the new line I added on the end of the arc is the second one).  I can drag the remaining degrees of freedom wherever I want and the tangent constraints continue to hold.

@johnsonshiue, can you or one of your colleagues explain what's going on here?

Sam B

Inventor Professional 2018.2.3
Windows 7 SP1

[kelly.young]

@SBix26 that's odd. Until you put the dimension on the arc it behaves erratically and goes all over. I'll forward over, see if there's anything else to investigate. 

[johnsonshiue · Accepted solution]

Hi Guys,

The behavior does look wrong but I think it may have something to do with restrictive nature of tangent constraint. An arc has quite a few degrees of freedom in the space. It guess the solver returns a sloppy solution quickly waiting for fewer DOF. I notice a very interesting behavior. Simply open the file and keep doing Rebuild All a few times. You will see the arc will move to tangent orientation. This shows that the behavior is indeed solver related. Tangent constraint does exist but it is not fully enforced.

I will work with project team to understand the behavior better and see what we can do about it.

Many thanks!

[kelly.young · Accepted solution]

@TobiasZetterberg2067 thanks for reporting the behavior.

This has been logged internally as INVGEN-13639