THANKS DJANKY for a good introduction.

FDM process or also called FFF or other names is now very open source. Unless I am mistaken, all the key patents have expired (but maybe Stratasys has a copyright on FDM). In the recent RAPID trade show in Pittsburg, PA, I saw no less than 15 machine manufacturers for this technology with at least 5 offering machines for INDUSTRIAL (not hobbist/maker) use. Many of these machines are with price points less than $10k USD and offer very diverse features and large (by historical standards) build sizes. 4

Also now, an offshoot of this technology includes using a pellet extruder instead of a filament which allows use of many engineering resins (injection molding grades mostly). This area is fertile for development. If enough people are interested, I can write a detailed post about this evolving technology which can be very exciting.