Im upgrading my machine. I bought a 4.5kw spindle - yep - looking forward to putting that baby on in place of the 2.2kw I have been using for years. My gantry is HEAVY. Gantry is made up of a timber beam 100mm x 300mm with a 6mm plate alloy on one side to attach everything too. And being careful I even balanced it. So the gantry being heavy and rigid is no problem. Its the Z axis with that weight and the Nema 23 I am wondering if it is too much.

What I am doing is installing another 8kg on my Z axis. Quite a lot really, and in that I have put 10Kg additional weight on top of the 2.2kw spindle to see if the Nema 23 will be able to lift it. And it did no problem. The Nema 23 is a closed loop stepper. Here are my questions:

1: I am building a new Z axis assembly, more solid, heavier linear guides, larger rails, larger plate alloy. I see there are heaps of calculations with ball screws. I am thinking I will just use the 1605 with a double ballnut. I wonder if I should look at the 1604 with the 4mm pitch to make it easier for the little Nema 23 to lift the additional weight? The double ballnut is twice the friction, but the 4mm pitch instead of the 5 is ummm 20? percent less to lift the extra weight?

Or am I putting too much thought into it and just stay with the 5mm pitch screw?