Can I create a Round that is tangent to only one surface?

Question

I am trying to create the round on the sharp end of a helical sweep but want to be able to specify the radius and dimension from the end of the sweep. They may not always result in tangency to the end face.

I have tried using a swept cut but it is really hard to keep it tangent to the helical surface in Cartesian since everything I am working on is really in cylindrical coordinates. Also, that method doesn't produce my desired result it just cosmetically looks close.

Using Creo 2 M130 or Creo 3 M090

i.e. If I want a 25mm radius round that begins 8mm in from the end of the helical sweep only tangent to the swept surface but intersecting the end face not tangent to it.

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dprieb · Accepted Answer

Well, if the round tool will NOT ever do this it forces my hand into another method.

I follow you with the offset plane and then using intersect to get the curve. I have tried that route before but the geometry you can't see on the screen made it tricky to get a trajectory for a sweep. When I used the intersect to create a reference curve I was able to get a section normal to it and then sketched my radius from the trajectory intersect to the end face. It worked good but left the sliver seen in blue outline. Flexible modeling remove surface took care of that.

Either way it works for large radii but would not build when I tried to make it go tangent to the end face...then I should just use a Chordal round.

dgschaefer · Answer

That's a bit like asking if there's a way to make an extrude that turns a corner. Extrudes go straight and rounds are tangent on both sides.

I cans see making an offset plane at your 8mm, create a curve at the intersection of that plane and the helical surface and sweeping a 25mm radius along it. Getting tangent will be the tricky bit, but I think it should be possible.

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