The Second stage is a little bit easier than the first one...
It mainly consists out of a screw in a pipe. Because real archimedes-screws are hard to find and very hard to produce without a 5-axis-CNC i decided to use the same trapeciodal-screw i used for the first stage: a 10mm screw with a 2mm thread.
On the bottom end the screw is plain, on the upper it goes into a 10mm coupling.
The other side of the coupling is connected to a stepper motor.
Screw and coupling lies in a alumium case i produced on the lathe, between the case and the stepper is a little seal to prevent the material getting into the stepper. On the height of the screw is a 4mm hole at one side in the case. This hole connects the hose from stage one to the screw, so the material is put into the second stage. If the screw turns, the material is pushed downwards into the nozzle and on the printbed.
Furthermore a heating quite similar to the one from stage one is wrapped around the lower part of the second stage.
This way a precise and heated material-flow can be generated.
Sometimes a picture tells more then thousand words, so...
Milling the case of the second stage
First test-assembling of stepper and screw
The heater for the second stage
All parts of the second stage before assembling
Don´t forget the seal between the case and the coupling! Otherwise it´s getting dirty...
The second Stage assembled!
Here you can download all sketches (SolidWorks):