1. I have 2x 269oz 2x 387oz 2x 425oz step motors from PH http://homanndesigns.com/store/index.php?main_page=index&cPath=25 my plan was to use a 269 for my X axiz and the 387 for the Z axis is this the best option?
I would think so, but maybe the heaviest axis would be best with the biggest motor.
2. I brought some Gecko G251 for the drivers assuming they would work fine - will they?
As long as the currrent of your motors are compatible they should work fine.
3. Is it possible to have a third axis that when enabled (with a switch) homes itself, then goes to the current z axis position, then mirrors the z axis?
Not sure about this, would need more explanation of what its actually for and when its going to be used.
1. My pendant controller is going to have two MPGs one each for Z & X i assume i can do this with mach.
No probs there as long as you have the Inputs Mach can handle 3 MPGs
2. The door should really be on gas struts which are expensive, what are your thoughts on having a air ram open the door? I have plenty of air rams and fittings so it wouldn't cost hardly anything.
No car scrappies in NZ? You should get a cheap gas strut there.
Air would work fine but adds complexity I suppose, just make sure you dont have too much air flow or you might get a Glasgow Kiss from the door
3. I would like to use the old mounts from the old z axis leadscrew if I do so ill have hardly any clearance (the center of the leadscrew is only 25mm away from the bed) if i do use this mounting position ill have to use belts as the motor center is 30mm to center. The X is belt driven anyway so its not a huge deal, if I do use a belt then i can gear the axis should I change motors and take advantage of the gearing?
I prefer belt drives rather than direct, much easier to set up as direct needs precise alignment. Both my mills and my lathe have belt drives even though one of the mills and the lathe are driven 1:1 and thats the way they were built by the commercial machine tool builders.
Hood