So I've been using Solidworks 2016 x64 Professional to help solve flat patterns for half-cones (among other things) for the past 6 months or so at my current job. I found a way that works involving a half-circle on the top plane for the bottom Diameter of the cone, and then a 3-D sketch the gives the height of the cone and another half circle that shows the top diameter. I then do a Lofted-bend between those two open profiles to get the cone geometry, which I then flatten using the flatten command.
This system has worked flawlessly up to about a week ago, when suddenly the flat patterns changed from a circular section to the flat pattern shown in the attached part that has no curves on the top or bottom. it just looks like a straight bar with angles cut on either end, which will not give the proper geometry.
I have a backup method of calculating the cones, but using a template file setup so I could just punch in the values was much faster and game me solid models to work with at the same time.
As far as I know, I didn't personally change anything. I've tried fudging the K-factor, changing auto-relief, removing auto-relief, different thicknesses, major/minor and height sizes of cones, etc. all result in the same final incorrect flat pattern. I'm at a loss.