I made this for a research project in a month. A printer for printing ice in sub-zero temperatures, to research new ways of building things with ice and snow.
It uses Openbuilds https://openbuildspartstore.com/ parts for all of the frame and mechanics. There's a Duet 3D WiFi controlling the printer and an external power supply for the motors. The "extruder" is custom, using low temperature hosing and changeable water nozzles.
This was designed to be a research platform, with modularity in mind, so converting this to other types of extrusion printers would not be too difficult. A challenging project which called for more engineering knowhow rather than industrial design, but it worked and made ice in the end.