I noticed that my poor Rambo 1.4 board has a lonely empty driver port. But I noticed that the image seems to show there are 2 z ports.
Are these two z ports tied together or can I use one as a rotary axis?
They are tied together so that you could drive two steppers, such as on 3D printer z-axes.
Also note, they are effectively wired in parallel. For driving two steppers (e.g. Lowrider which has two Z steppers) it is much better to drive them in series, so it is better to use a series wiring harness and leave one of the Z ports empty anyway.
A 4th axis is definitely possible using one of the extruder ports. A 4th and 5th axis should be possible using both extruder ports but I haven’t seen it done yet.
The trick to a fourth axis is not the hardware, it’s the software. The bulk of the CAM programs out there that do fourth or fifth axis are not cheap, and the rest of them are even more expensive…
What you can do is swap a rotary axis in for the Y axis. That allows you to do stuff like inlays on a dowel with the same software we use for the more typical X,Y designs.
I can’t do any of these though… I have dual endstops wired.