Z-axis rotation indicator

The subtle movements of the z-axis can be hard to see, it is usually less than a millimeter during moves. The rotation of the z-axis is usually bigger, but even that is hard to see. This thing adds an indicator making the rotation more visible. Its construction make it easy to add, without any disassembly and reassembly of the printer. All it requires is two different colours of filiament. You need four things for a complete indicator.

The location is chosen to not interfere with X-axis assembly movement.