Leadshine EM806 - Am I using them properly?

[Chaz]

Re: gearing.
1:2 or 2:1.

1600 rpm for a nema 34 stepper sounds extremely high.
Typical is 800 rpm, or less.
4m/min = 66 mm/sec.
A 5 mm screw at 1:2 = 10 mm per rev of motor.
So 12 Nm /2 == 6Nm stall and maybe 3 Nm 300 rpm.

At 1:2 you would have half the torque vs direct gearing.

For 10 mm /rev, 4000 mm/min = 400 revs/min.
6.6 rps.

Anyway, if as You said the threading ignores acceleration settings, then maybe / probably the problem is lack of torque on z past 200 rpm at spindle.
The z axis tries to accelerate to a speed suitable for the spindle rpm, and cannot do it.
The z axis maybe tries to accelerate "instantly" to the required sync speed, and simply does not have enough torque to get there before stalling.

If gearing 1:2 motor/screw your screw would run at 3200 rpm at 1600 from stepper.
That is probably wrong.
2:1 is probably right.

Anyway 4m/min on a medium lathe like yours, and gibs, is far too fast.
It will wear out your mechanicals real fast.

My lathe is about the same size, 12x24.
On servos with 10x the acceleration and 5x the speed my rapids are much lower on purpose.

Thanks. Ill check the maths later.

You are right, its the initial acceleration to sync to the spindle which is a problem. What I struggle to understand is why does this only happen towards the chuck and not from it and why does the first pass work? I did this a few times yesterday, same result.

My other lathe has a much much finer ballscrew, it has no problems and whilst I dont know the exact motor spec, its not nearly as powerful.

This is why I love servos. Oh well. Time to gear the Z down somewhat I think.