A screw press is used to remove liquids from solids by compressing the solids to drain the liquid. This is a dewatering process, where you press organic matter (such as cow manure) to remove most of the moisture which takes up space, adds weight and makes the organic material less combustible.
Parametric design done in Autodesk Fusion 360. Find Fusion link here: http://a360.co/2saqamA (note that core and screw are two different bodies, but needs to be combined for printing. The included stl files already take that into concideration)
This version is just over half a meter long and was cut into 3 pieces, each around 200mm high since the printer I used can print 350mm high. If you cannot print this high, feel free to rework the file.
The screw and core is printed, while the bowl (or pipe around) is 75mm (3") PVC pipe with a T-Piece and end cap at the back. Threaded rod and lock nuts were used to secure the core and give it an axis to turn around.