Hi guys, my first post after following this forum for months. I hope you've all recovered from the festivities:)

I am converting a Sieg SX2.7. So far I have converted the X and Y axes with bog standard chinese ballscrews, and Nema23 2.2Nm direct drive (i.e. no pulleys) , driven by Leadshine EM806, 68V psu.etc. So far so good.

For the controller I am using Kflop with KMotionCNC. I've tried a couple of the little cheapo chinese stand-alone boxes that were discussed in another thread. Although they moved the machine OK, the movement (particularly around arcs) just sounded a bit clunky compared to the silky smoothness of the KMotion. For many other reasons (particularly stability) I settled for KMotion, also tried the KFlop with the Mach3 plug in, which worked just as good, but to be honest, I kind of prefer the simplicity of the KMotionCNC.

Anyway, now I am at the stage of doing the Z axis. I've taken the old leadscrew out, luckily the existing ballnut support can be reused, no need to machine a new one as the standard ballnut with the six bolts fits perfectly in the hole (though only using 4 of the bolts).

BTW, the X axis was more difficult to fit, as typically there is very little room under the table for the ballnut, a little grinding of the saddle was necessary, which I did partly with a manual mill and then the Dremel to get a nice final finish, so it wasn't too dramatic. The un-ground rough part of the saddle casting wasn't level, so some material had to be removed for the length of the ballscrew to have clearance.

I am thinking of using a slightly more powerful motor for the Z, Nema23 3.1Nm. and my question is....do you think I can get away with coupling it direct (I use Oldham couplers) , with no pulley 2:1 reduction? My initial thoughts are to try it direct to start with, and if I notice that the motor struggles or looses steps when cutting, then it doesn't take too much effort to machine a new plate to house the pulley reduction and put the motor to one side. Direct coupling looks a bit more elegant and it's easier to fit, but it's no good if it doesn't work.

Since what I think I've learned from this forum is not to use motors bigger than necessary, I wonder if, from your experience, you think that direct coupling for the Z will work in this case.

The only other observation is that I have both the EM806 and the AM882 drives and with identical settings, the EM806 whistles a little on standstill whereas the AM882 is completely silent. Both are very quiet and very good when moving, with a very subdued mellow Symphony that is delightful to the ear:)

Edward