Why two motors for Z axis on Mendel?

[davidfcox]

I am interested in design decisions. My instinct would have been to use on motor for the Z axis and use a belt drive to drive the other. Someone pls make me wiser.

[MeoWorks]

I'm no expert but I'd imagine it's a balance issue since the Z relates to the X carriage which has a big honking motor on one side of it. So I would imagine it'll be easier to move the Z up and down using two motors+threaded rods than just one motor that has to drive a belt as well.

[RP Iron Man]

Also. if you only use one motor, you would have to drive the dual z lead screws using 2 pulleys and a belt, which pretty much adds up to the cost of the motor you just replaced... In the end, it's easier to just use two motors for the Prusa Mendel design.

Eric

[etmh]

On the other hand, the Vellaman K8200 lifts the z-axis on one side only. Of course it isn't lifting the weight of the x-axis, since it has a horizontal xy table.

[Hårball]

The reason for this is mostly simplicity, and as before mentioned, a stepper motor is circa the same price as the belt , two pulleys and one idler would cost, also you would need a seamless belt because of the multiple rotations one would need to lift the z axis.