Manual Z-axis for Neje laser modules

This is a manually-adjusted Z-axis for laser engravers without a real Z-axis. It is very similar to my Thing:5137835 but without the stepper motor and with parts adjusted to accept a knob on the end of the leadscrew. The rails and linear bearings can be either 8mm polished rod and LM8UU bearings or plain 5/16" drill rod and printed linear bearings as shown. Plain 608 skate bearings capture either end of the leadscrew. The carriage will accept the 30mm body of both old and new Neje laser modules and lightly-adjusted clamp screws hold it firmly in place. All other hardware is common 3mm machine screws/nuts. Max travel range is ~70mm.