Closed Loop stepper response "Slower" than Y axis open loop stepper?

[Corchenko (Yair Alejandro Posada Urrutia)]

Hi there. (First of all sorry for my bad English)
I have build my CNC C02 laser machine (1200mmx1200mm) with Nema 23 steppers, and it cuts and engrave bery well but it is a little sloow in order to not lose steps. I have too a CNC Router with Nema 23 Closed loop Steppers, that works pretty well and fast, so i decided to upgrade my X axis Stepper to a Closed loop one, it is a Nema 23 3nm 1.8°. So, I replaced the old motor with this new one, calibrate the steps/length… but heres the problem even knowing this motor is faster than old one the response of this new motor feels like “slow” i mean like if it has lag, so when I tried to cut a circle it draws something like an egg, the laser starts cutting before than the motor is in the first coordenates of the work so when the cut finished it apppears like it have a “tail”
When I try to engrave the laser engrave lines before of the nozzle enters in work area (when nozzle comes back to engrave the line also starts before) this occur exactly the same with slow and fast speeds
I hope someone can help me.
Thanks

[ednisley]

@Corchenko

the response of this new motor feels like “slow”

The discussion around this post may be relevant:

Intentional Firing Delay

Hello there. I have a problem that requires introducing a 12ms delay at every firing sequence (either hardware or software wise). So let me explain the problem. I have changed my X axis of a Chines laser with a DC servo motor that is able to go up to 3000mm/sec, mechanically everything is fine and max speed is achieved without any problem. The problem though is the way the drivers is designed, due to the complex algorithms for PID and advanced tracking options there is a delay of approximately…

The motion planner assumes both axes have the same overall behavior, so a motor with a slow response time cannot produce proper motions.

If you upgrade both axes the motion may improve, but the laser will still fire at the wrong time.

[Corchenko (Yair Alejandro Posada Urrutia)]

Thanks for answer!
Reading the post that you forwarded I have seen in my control an option that says something like "Transmission type: Stepper/Belt, Stepper/Screw, Servo/Stepper, Servo/Screw. Normally it stays in stepper/belt, when I installed the closed loop motor and see the mess that the machines were doing, I change it to Servo/belt but I do not botice any change, still messing with the laser, I guess it is because the Y axis is still an open loop stepper… so, do you think if I upgrade the Y axis to a Closed loop and put the machine on servo/belt would cut correctly?

[ednisley]

@Corchenko

do you think if I upgrade the Y axis to a Closed loop and put the machine on servo/belt would cut correctly?

No, because the laser timing will not take into account the response lag in the XY motion.

The laser controller assumes essentially zero time delay after it sends a step pulse to the motor driver. Your servo driver + motor combination does not match that assumption and will not work correctly.

@Corchenko

it is a little sloow in order to not lose steps

Perhaps reducing the acceleration for both axes, particularly the one driving the entire gantry, will allow it to reach a higher top speed without exceeding the motor torque limits. When the acceleration is too high, the motor cannot “shove” the machine’s mass hard enough to get it up to the commanded speed, so the motor stalls.

Torque is also a function of motor current, so you have several knobs to adjust while tuning the machine.