I'm working on a sheet metal part, which is essentially a cone with one or more flights winding up the inside of it:

We will have both the cone and flights lasercut from flat patterns, then will roll the cone and weld the flight up the inside. 

Is it possible to create line on the inside of the cone, which will flatten correctly and can therefore be drawn on with the laser. Then this path can be followed when welding on the flight to make it quicker and more accurate.

I can create a curve on the intersection between the parts, but it doesn't 'stick' to the cone flat pattern. I guess it would need to be basically a zero thickness line dividing the face.

How can this be done?