If you want to turn those napkin sketches into a 3D printed product you are going to need computer aided design (CAD) software. The CAD industry has been going strong since the 1980s and includes various levels of sophistication from simple 123D apps to industrial level software such as PTC Creo. Based on conversations with teachers the best entry level software for CAD is Sketchup and TinkerCAD. If you want to take it to the next level, check out PTC Creo as it is free for students and teachers. Some big takeaways from using CAD software in the classroom are high levels of student engagement, creativity, and opportunities to apply STEM concepts to the modeling process.