I'm currently almost rebuilding this printer as I'm dissatisfied with certain aspects of it.
The Z drive with the 4 threaded rods is very noisy and slow.
The brackets for the bed failed to hold it when printing with a high bed temperature so I had it supported on pieces of wood on the floor.
In spite of the bungy cords to lift it, the umbilical tended to catch at high level printing.
The arrangement of Z drive and XY carriage limited the printing area.
To overcome these problems I'm changing from moving the XY plane for Z axis to the more standard moving print bed, replacing the 5mm thick aluminium bed with a 2mm aluminium sheet supported on aluminium extrusion, parts of which will form the Z carriage.
The threaded rod Z drive will be replaced with cord support on the four corners as I have in one of my other printers. The cords will be taken over pulleys to a crosswise bar on which they will be wound up to lift the bed, with the bar driven by reduction spur gears (3D printed) from a stepper motor.