How many stepper motors for a Prusa with Wade-like extruder?

Hi. I'm a bit confused about how many stepper motors I need to build a Prusa.

I am planning to use Greg's hinged accessible extruder (a variation on Wade's extruder).

I know the standard recommendation is to use the NEMA 17 motors - and I can get these via mendel-parts.com, thingfarm.org, or any other number of sources. What I don't know is whether I need 4 or 5.

Obviously one is needed for each of the cartesian axes, and one for the extruder also. So that gives four. Is that it? Or is a fifth one needed also? And if so, what exactly is it's purpose?

Looking at the Gen7 PCB board, I see connections for only 4 motors - not 5. On the other hand, the Prusa documentation states that 5 are needed. Hence my confusion.

Can anyone clarify?

Prusa requires 5 motors because the Z axis requires 2 motors. I use a RAMPS 1.3 that has two motor connectors on the Z stepper driver, but if the board doesn't have 2 headers can just connect the motors together before going into the board (doubling up the motors on one stepper driver).

Edited 1 time(s). Last edit at 08/04/2011 05:39AM by loheiman.

If it helps, section 13 in the following link shows (roughly) how the Z motors are connected.

[issuu.com]

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garyhodgson.com/reprap | reprap.development-tracker.info | thingtracker.net

Thanks for the clarification gents. The documentation looks good Gary!