Hi,
with a 1605 ballscrew on the Z axis you will need a stepper capable of high speed due to the fairly fine pitch of the screw. A 1.8mH inductance stepper as you have
proposed should be capable of 750 rpm with about 50% of rated torque which I think would work well.
It is possible that the Z axis could slump when the stepper is powered down so a brake would be a good idea. Having said that the vast majority of users do not have
a brake and get away with it just fine.
It may be that you have to fit a spring or counterweight so that the Z axis does not slump, many people have used that idea.
The 34 size steppers you are proposing for your X and Y axes look pretty good. 2.8mH is pretty respectable for 34 size steppers. I think you are being optimistic that they will
do 1000 rpm. Large motors with comensurately high inductance will not spin fast. I think it more likely that 500rpm is about what you will get.
I notice that you have selected closed loop stepper and presumably you are happy to pay the extra? The manufacturers claim they are faster, more powerful and never lose steps....
all pure BS. Closed loop steppers do have some advantages but not all that is claimed by the manufacturers.
If you use adequately specified open loop steppers and use them within their limits they will never lose steps, after all many people have operated that way
for many years. So if an open loop stepper never loses steps then why bother with the expense of closed loop?
I would commend you consider open loop steppers but of EVEN LOWER INDUCTANCE with the highest voltage drivers and power supply you can find.
For example these 24 size steppers are only 1.18mH:
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and matched with these drivers:
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I would use the same steppers throughout your machine. With 1.18mH inductance and 80VDC drives and 80VDC power supply you could expect to get half their rated (3.1Nm) torque at 1000rpm, ie 1.55Nm.
These steppers will probably out-perform the bigger motors at speed.
Craig