AASD Servo driver and torque problem

4Nm is quite a small torque. Maybe try setting a torque wrench to that level to calibrate your hands and see if the motor is genereating a similar torque at low speeds.

However, looking at this tapping torque calculator, 4Nm should be enough for M16(!) in Aluminium, so it sounds like you probably are low on torque.

A servo motor should make rated torque at 0 rpm. That's prety much their job.

Hello, the revs should not play. Are the values ​​of the pid regulator default?
This is my other 1kw motor with a hard setting on the pid regulator.
ps: the watch has a resolution of 0.002uM, a belt drive of 1:1 and a screw pitch of 10mm.  The motor has 2500 rpm
From 22 seconds I apply great force.

After conducting numerous experiments, I have established the following parameters:
Pn259 = 6
Pn275 = 1.20
Pn020 = 3000
Pn098 = 20

These settings enable the motor shaft, when connected to the spindle, to operate comfortably up to 1500 RPM with manageable noise levels. However, beyond 1500 RPM, the noise becomes extremely loud and problematic. Another issue arises when attempting to decelerate the spindle from 1500 RPM to 0 RPM. During such attempts, the servo driver immediately displays the well-known error from my first post - AL-04. To avoid this, I need to first reduce the speed to 1000 RPM, then to 500 RPM, before I can safely stop it without triggering the error.

Are you running your spindle server in position or speed mode?

I run mine (Lathe) in speed mode - set PN002 = 1 (speed mode) or 3 (position/speed mode).

The last option will allow you to switch (via input signal) between modes in certain situations.

Then look at your settings PN146 etc (speed control parameter) and define your acceleration / deceleration times.

You need to set a speed ramp / acceleration.
Usually the drivers come with a factory setting that can run the motor without noise.
Have you tried playing with the pid settings Pn115 -pn116; Pn153-pn156

Ps: I think they are trying to work in positional mode.
First make the motor move from the driver's keyboard, then with linuxcnc

Firstly, I'd like to thank all of you for your answers!

I'm using the motor in positions mode (Pn002=2) with step/dir pulses from a MESA card. When I run the motor on its own, without connecting it to the spindle, everything works perfectly out of the box. I can go up to 3000 rpm without any issues, tested with both LinuxCNC and the jog function Fn002. The problem arises when I connect the motor to the spindle using an HTM 5M belt.

My question now is, can I drive the motor in speed mode using step/dir pulses, or do I need to use -10/+10 voltage for that?