It started as a private message on bimmerforums requesting that I produce something called "dohickies". The "dohickies" are roof rail end caps for the BMW Z3 MCoupe and Z3 Coupe. They are hard to find and disappear easily. To purchase new, it requires purchasing a whole new roof rail solely for the plastic end cap. As both of mine were intact and not missing, I decided to take on the small challenge.
First step, scanning the plastic end caps with a 3D scanner to get an accurate digital reproduction of the part for reverse engineering or measuring the part and reverse engineering it manually. Both require skills at a CAD program like SolidWorks or Rhino5. Since we have a decent laser based 3D scanner at our shop, I scanned one of them knowing that the other side is a mirror image. After cleaning it up and getting rid of the extra data, I ended up with a digital dohickey.
After scanning the part and inspecting the roof rail closely, I decided to take a few design liberties over the original that would make prototyping and production of the part quick and make them stay in better. Loose dohickies are never a good thing.
Rapid prototyping is quite amazing. It allowed me to do all the R&D in a single day. 3D printers have come a long way since first being invented in the 80's and the market for them has exploded in the past couple of years. Tweaking the design little by little to get the part to fit right is an essential part of the process and having a 3D printer makes it much easier. I went through 5 iterations before finally landing on a part I was happy with.
3D printing was the quickest option to manufacture the parts as well. Since we have a filament extruder 3D printer, they don't come out clean and need quite a bit of work to make them ready to sell. Since the parts are small, it involves adding plastic to prevent sanding too deep and lots of sanding, followed by paint.
They are currently available in our shop if your dohickies are missing.