Some questions to JAZZCNC or any other closed loop stepper experts

[A_Camera]

OK, thanks. Anyway, there are AC servos which use less voltage than the mains, but in all cases they require a beefy transformer, a large driver and even the motors are larger. I have no space or need for that at this moment, even if it would be much better for the purpose. Remember that this is mostly just a test, a proof of a concept with a goal to build something to play and learn with.

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. Basically, I have written off the use of closed loop stepper, mainly based on what Dean said before, except that I will not at this stage buy a large one, but aiming at a 180W type from JMC, namly this one:

https://www.aliexpress.com/item/3294...79092e0eprgamN

I checked the manual and the software, and must say I am impressed considering readability, configurability and contents, and since this will be my first servo, I think that is important. It fits my size needs and I don't have to build a new PSU / control box. If in the end it turns out to be too weak, I can always move the motor to my CNC and replace a NEMA23 stepper of one axis, and buy a new and stronger servo with break as Dean suggested, but that will not be now. First I want to finish the project and see it working.

I think you are wrong about gearing. Torque is multiplied by the gearing, so indeed I gain a lot. Of course, since the stepper is pretty weak, it will not be much at high RPM, but never the less, it will be six times (minus some losses, but we can ignore that here). Of course, gearing down is giving the most torque benefits in holding, but there is a benefit even when rotating. Of course, that would not be needed at all if I had a large enough motor, but that's for later times.

[Muzzer]

I think you are wrong about gearing. Torque is multiplied by the gearing, so indeed I gain a lot. Of course, since the stepper is pretty weak, it will not be much at high RPM, but never the less, it will be six times (minus some losses, but we can ignore that here). Of course, gearing down is giving the most torque benefits in holding, but there is a benefit even when rotating. Of course, that would not be needed at all if I had a large enough motor, but that's for later times.

You seem happy to redefine terminology, which is fine but may cause confusion when you try to communicate with others.

Have a look at the torque-speed curves for the stepper motor you are considering. If you fitted a 2:1 reduction gear you'd double the stall torque perhaps. But if the torque at a new, doubled operating speed had dropped to half of what it was, you'd have gained nothing - you'd now have the same final torque at the same speed but you would have halved your max speed (the all important "rapids"!). My conclusion is that you might as well go direct drive with steppers.

For a servo it's different - you really need to step the speed down by a factor of 2 or 3 to boost the final torque to something more generally useful. Also, not many ballscrews will be happy to run at the max speed of a servo which is usually around 3000rpm, give or take. So to me, steppers are best used in direct drive and servos best used with a belt drive reduction ratio of between 2 or 3. But as I said, there's no right or wrong!

[Muzzer]

Here's a randomly chosen image from Oriental Motor, showing a typical torque speed characteristic for a stepper motor:

https://www.orientalmotor.com/steppe...er-motors.html

If you gear down the output by 2:1, you might move from eg 500rpm to 1000rpm and in the process you'd drop from a pullout torque (loss of position) of ~45oz-in to 27oz-in (forgive the Mercan units). After the supposed doubling up of torque through your expensive reduction stage, you'd actually end up with ~54oz-in. That's an increase of ~20%, not 100%. See what I mean? Some of the Chinesium steppers have even worse torque curves. Sure, you double the stall torque but unless you plan to use your machine as a press, that's not much use to anyone.