There is a patent for a 3D printer enclosed in a box. A number of plastics print much better when in an enclosure with no drafts and more easily controllable temperatures.
But instead, 3D printers must be sold and function on their own without a box, to avoid the patent. Enclosures are then sold separately and you end up with a 3D printer in an enclosure anyway, but that doesn’t infringe on the patent… so it’s allowed.
I assume you are talking about this Stratasys patent that expired earlier this year, https://patents.google.com/patent/US6722872
> 1. A three-dimensional modeling apparatus comprising a heated build chamber in which three-dimensional objects are built, a base located in the build chamber, a dispensing head for dispensing modeling material onto the base, the dispensing head having a modeling material dispensing outlet inside of the build chamber, and an x-y-z gantry coupled to the dispensing head and to the base for generating relative movement in three-dimensions between the dispensing head and the base, characterized in that: the x-y-z gantry is located external to the build chamber and is separated from the chamber by a deformable thermal insulator. [...]
If we abolish patents innovation will finally be possible.