I got a parallel sided cardioid tube to open out but haven't had time to try to a truncated cone!
Always enjoy a challenge!
Lunchtime- made as a sheet metal part.
Swept blend and used the thickness setting rather than offset in sketch.
Can rip on a corner. Now just need to sus flattening!
Peter using a round got me thinking and I managed to get a parallel sided shape to flatten in sheet metal but as soon as I added a draft it caused the flatten to create a weird partially curved shape.
OK, to get a complex part ripped and developed to a pattern, I did surface rips and removed difficult sections, flat pattt\erned it, saved as.
Then opened original and removed other sections, repeated. It took 3 goes but could then assemble the various flat patterns to get what we needed. The MAKER had already used some old technical drawing gear to do the task while I fiddled, but we know we can do it next time. I will post a photo of the Mushroom(actually a CACTUS called Lithop) stool. Thank you all for the effort and your time.