Thanks for that post - interesting approach to flattening.

The thing with Sheetmetal every shop will have different capabilities with the tools on the factory floor. Even in a set CAD sheetmetal design environment just because you design a part that you can flatten doesnt mean it can be manufactured. Many factors like bend sequence tightness of bends all contribute to what a manufacturer can handle and produce. But the main thing that I have seen change last few years was 2 years ago I was producing sheetmetal parts then flattening to a 2d DXF and sending a PDF with bend sequence dictated by me.

Its been ages since I have done that with most shops these days wanting assembly 3d STEP files it gives them the part quantities and they flatten on their end with software like AUTOPOL which has their machines and tool library setup within. Much better than generic flattening from something like Solidworks or Inventor Sheetmetal which are still great.

Many new brakepress machines are starting to handle direct loading of 3d STEP files on the controller this gives the operator visual guides on bend sequence with which way a up or down bend is to be positioned.

Sheetmetal manufacture is changing fast but the best is to team up with a sheetmetal manufacturer that has the capabilities for the parts your after. They will tell you very quickly what you can and cant design learn from trial and error - in the end hopefully not too many errors.