Internal loft fails with tangent condition

[awc.sorensen]

I'm attempting to make a duct inside an existing solid, when lofting from a sketch defined on the outside faces the loft works without fault. However if I extrude (cut) into the solid and then loft off the projected sketch I only get a successful loft using the free condition.

I've attached a very simplified version of my part with a free condition loft, but I run into issues using tangent & smooth conditions.

Any help is appreciated!

[johnsonshiue · Accepted solution]

Hi! The reason why it fails is because the tangent target is ambiguous. The edge loops you select both have two sets of faces to be tangent target. There are two ways to get the desirable result.

Option A: Instead of using edge loops, you can simply create two sketches by projecting the edges. Then select the two sketches to loft. There isn't tangent control but there is angle control. You can set the takeoff angles to 90 deg and appropriate weight value. The weight definition is slightly different than the face loop tangent weight. You can tweak it a bit and see what value works best for you.

Option B: Use Thicken/Offset command to create zero offset surfaces. Offset -. select the side faces (rectangular side faces on one end. Repeat it to the cylindrical face on the other end. Now, make the body invisible so it is easier to pick. Loft -> surface -> pick the edge loops -> you can set the tangent condition. You will get a Loft surface. Simply use Split or Sculpt to cut the solid.

Many thanks!

[awc.sorensen]

Thank you for the feedback, solution A works easily enough!

However I'm having trouble with option B, I can't seem to get the surface to loft from the circular loop to the 4 faces of the rectangular zero offset surface. I am only getting 4 individual closed loops so my loft tries to output a loft which zigzags between the selected 4 faces.

From what I can see it's acting the same way as the original, like what you pointed out about there being an ambiguous tangent target.

[TheCADWhisperer · Accepted solution]

What version of Inventor are you using?

Have you installed all Service Packs and Updates for your version of Inventor?

With the attached example you can set to Tangent or G2 Smooth.

[johnsonshiue]

Hi! It should work. Please attach Option B file here..I would like  to take a look.

Many thanks!

[awc.sorensen]

Your solution exactly what I wanted! Thank you!

I'm currently using a 2016 build 138, I've only realised recently that my application manager has corrupted/broken, I just haven't got around to reinstalling the full suite to amend it