reposition motors?

[damian238]

The bracket that moves along the Z-rail doesn't necessarily need to carry the motors. Instead, the same pinions used to drive the X-axis and the print-head rotation could be powered via belts, using a simple offset from motors mounted at the base. This would substantially reduce the mass for Z moves only, so maybe not worthwhile?

[Bolado]

That's how I pictured the idea, although a challenge that I see with this would be the binding with the pulleys to make the X belt move.

Also, to be honest, quite a few of end-user cartesian printers out there, specially bed slingers, the Z stepper carries the weight of the X stepper, but I see the concern, one stepper on the Z carrying the weight of the whole gantry + 2 steppers.

[damian238]

Yes, that's exactly right. Plus, lower inertia improves a lot of things. Picture the stepper pinion's current position (with slight offset) only connected to a drive pinion where the stepper is now. They could be tensioned the same way as the other side (with three pinions providing a "wrap around") only they'd be on the stepper side on the carriage. It just doesn't seem necessary for the z motor to have to shove all that mass around (never mind doing it quickly).