Some questions to JAZZCNC or any other closed loop stepper experts

[m_c]

Correct me if I am wrong, but don't say that I "happy to redefine terminology", because I am not. I did not make any calculations before, but definitely not redefined anything and torque is definitely increasing when you add a reduction gear. I think you understand that very well, but if you don't understand what I am saying that's a different thing, and is perfectly possible that I am not that clear, but that does not justify such statement. I am not stupid, I can read charts, make calculations (in ANY sort of units) and so on. You are not the only one with engineering background and long and prosperous career.

Erm..you did though -

I think the only difference between AC and DC servo is that an AC servo driver has the rectifier built into the driver, while a DC servo must be fed using an external DC PSU with a rectifier circuit in the PSU. When I say DC servo, I mean just that the driver needs DC current, but it is still a servo, and NOT a closed loop stepper.

How any given motor controller gets powered, does not define the type of motor attached to said controller.
An AC motor doesn't suddenly become a DC motor because the controller needs DC power.

[A_Camera]

Erm..you did though -

Where and in what way?

If you have a 1:6 gear you WILL get a 6 times increase of torque at ANY given rpm between zero and infinity. Period.
If you have a 1:6 gear you WILL get a 1/6 reduction of rpm at ANY given rpm higher than zero rpm. Period.

What is wrong in the above two sentences? If something was not clear in anything I said before then of course, a clarification should be asked for, but with an explanation of what is not clear, or what is wrong.

Of course, it should be clear and obvious to anyone that I don't mean the holding torque. Holding torque is only multiplied by six at zero rpm. For a servo if the torque is constant, the increase is 6 times all the way. Isn't all that true? I mean, I am an engineer (with more than forty years of experience and a few of my own inventions), but not on the mechanical side and I may have missed something, or didn't use the right expression or words, but that's not the same as I am a stupid idiot who is trying to redefine the shape of the earth or something. However, without explaining my mistakes nobody is helped and nobody is learning anything.

But OK, this is the Internet...

How any given motor controller gets powered, does not define the type of motor attached to said controller.
An AC motor doesn't suddenly become a DC motor because the controller needs DC power.

I know that, and as far as I remember, I made that clear before also. Some people talk about AC (powered) servo as if it was something special. The only special thing about them is that the rectifier is built in the driver, because otherwise internally, I think they are the same. But of course, I never had one, never opened a driver for a servo, so I don't know for sure, but I strongly suspect that is the case. The only advantage is when you have really high powered servos which can be fed directly from the wall mains. It makes wiring much simpler. Of course, it is simpler also if all you need is a transformer, but if you already have a fat PSU with a good enough voltage then there is no benefit in going to AC powered servo, unless you need to replace that PSU due to the size of the servo. In that case, of course it would be dumb to buy (or build) a new PSU when one can use the AC directly from the wall.

[m_c]

Where and in what way?

If you have a 1:6 gear you WILL get a 6 times increase of torque at ANY given rpm between zero and infinity. Period.
If you have a 1:6 gear you WILL get a 1/6 reduction of rpm at ANY given rpm higher than zero rpm. Period.

What is wrong in the above two sentences? If something was not clear in anything I said before then of course, a clarification should be asked for, but with an explanation of what is not clear, or what is wrong.

Of course, it should be clear and obvious to anyone that I don't mean the holding torque. Holding torque is only multiplied by six at zero rpm. For a servo if the torque is constant, the increase is 6 times all the way. Isn't all that true? I mean, I am an engineer (with more than forty years of experience and a few of my own inventions), but not on the mechanical side and I may have missed something, or didn't use the right expression or words, but that's not the same as I am a stupid idiot who is trying to redefine the shape of the earth or something. However, without explaining my mistakes nobody is helped and nobody is learning anything.

But OK, this is the Internet...



I know that, and as far as I remember, I made that clear before also. Some people talk about AC (powered) servo as if it was something special. The only special thing about them is that the rectifier is built in the driver, because otherwise internally, I think they are the same. But of course, I never had one, never opened a driver for a servo, so I don't know for sure, but I strongly suspect that is the case. The only advantage is when you have really high powered servos which can be fed directly from the wall mains. It makes wiring much simpler. Of course, it is simpler also if all you need is a transformer, but if you already have a fat PSU with a good enough voltage then there is no benefit in going to AC powered servo, unless you need to replace that PSU due to the size of the servo. In that case, of course it would be dumb to buy (or build) a new PSU when one can use the AC directly from the wall.

And as per usual, you completely missed, or simply chose to ignore the bits Muzzer and I were correcting you on, with a big long rambling post.
I'm out. Have fun, interpreting things in whatever way you wish to chose, even if that interpretation is completely wrong.

[A_Camera]

And as per usual, you completely missed, or simply chose to ignore the bits Muzzer and I were correcting you on, with a big long rambling post.
I'm out. Have fun, interpreting things in whatever way you wish to chose, even if that interpretation is completely wrong.

...and that is called constructive comment...?

Bye...

[routercnc]

I have just skip read this post but the following video released by Clough42 as part of his lathe electronic leadscrew motor selection shows comparison testing of steppers and servos. Might be of some interest:

https://m.youtube.com/watch?v=et3oXoA2Hqo

[A_Camera]

I have just skip read this post but the following video released by Clough42 as part of his lathe electronic leadscrew motor selection shows comparison testing of steppers and servos. Might be of some interest:

https://m.youtube.com/watch?v=et3oXoA2Hqo

Very interesting. Thank you. In the meantime, I bought a 180W servo motor, but to be honest, I am so far not impressed by that one. I feel that the holding torque is really poor, but maybe there are some parameters I missed and it can be configured better. However, this is version 552, and those have been replaced with version 6 which supposed to be better. I actually complained to the seller because he sold it as the "latest version" but it was obvious that it's not. I contacted the factory and got a reply that this version should not be sold overseas any more. Then I contacted the seller again and he offered me 100% refund, which was accepted. So now I have a free servo I can play with, but in the end, I may need to buy a 400W version if I want good holding torque also.