Traditional Stepper vs. StepSERVO motors

[telelaci]

- 0:35 "...flip the switch and see who finishes first..." - both kind of motor steps 1 (probably 1.8 degree) when gets a pulse. Who finishes first ? That one who gets the more pulse per second. Thats a control parameter and depends on you, it has nothing to do with the motors. The servo goes faster becose you controlled so, and you wanted so. But If you want that, the regular stepper goes faster, it depends on you how do you control them.
- 0:45 "85% greater torque allows to finish it faster...." - You donno the difference between speed (revolution/second) and torque. Torque has nothing to do with speed, as I said before the speed was higher because you controlled so. Both motor moves the same weight on a similar car, if we put the fragment of second long acceleration phase aside, both motor gives about the same torque in the above example, because their load is about the same.
If we compare the torque/revolution curves of these motors, then a stepper goes a slightly lower indeed, but those differences are little, and significant only at higher revolutions 1000 rev/min and higher up to 3000. Most of regular steppers can't even rotate a 3000rev/min, they are designed to low speed. At low speed (like the above test) the torque is about the same, and because the servo was set to 85% higher speed, most probably the regular stepper could give more torque in such a comparison. Could. But in the above test they had the same load they gave the same torque, as I said before.
PCB you donno the basics of physics and you teach people. Hmmm.
- 2:00 "more repeatable positioning and more accurate performance" - of coures you don't get more accurate positioning at all, you don't understand it PCB. If overloaded, both motor couse fatal a problem on a CNC machine, a spoiled workpiece. The regular stepper stalls (stops and humming only) when overloaded, the servo motor doesn't stall but slips . The real difference is the error signal ! At a servo you'll know about the problem at a regular stepper you will not know (your controll computer I mean) if a failure happened.
You stage things up and you say silly false things to sell a servo motor. Of course the servo is better anyway, but it should be, you pay 2 times more for it.

[Renaldo]

The traditional stepper motor used is a closed loop (not open as shown in the video) stepper motor with built in encoder and driver. This is quite an improvement from the real traditional open motor with separate driver without encoder. The price difference for that improvement is little compared to upgrading to servo motor.

[arashi]

PCB Linear, thanks for the video. I'm absolutely no stepper/servo expert, I just work with them regularly and there are a few points, I noticed didn't seem to reflect with my experiences:
- You can use encoders on steppers too, also making it closed loop. It's not unique to servo's.
I have done this in several projects, although in my experience, I agree closed loop systems seem to be easier with servo's. (Especially when you start fine-tuning)
(btw, I've also done this with 3 phase asynchronous motors and frequency controllers, which was not ideal but worked sufficiently stable for that specific application)
- The position of the box with the controller electronics, that depends on what you buy.
I always keep the controllers away from the motor, which is much easier to diagnose and replace, if problems occur.
Example: in CNC machines, there is too much cooling flying around, so controllers in the control cabinet, motors in the machine.
(but that's just my opinion and experience. I also saw 3 phase motors with frequency controllers built on the motor.)
- Servo's are not necessarily higher torque or more accurate. It also depends on the motor/gearbox combo and the way it is controlled.
I've managed to get a precision with steppers of 20µm (closed loop) and quite some heavy loads, but it was and yet, relatively low cost.
Servo's would probably have been the better choice here, but were quite a bit more expensive in that particular application.

[arbjful]

Is the motor same as the one made by applied motion??

[nirophek]

When the driver is on the motor it will get hotter, not cooler! it is bad for the driver, and if one fails so is the other and you have to replace both. I don't think it is such a great setup. And the servo motor is so cheap today I don't see any reason to use the stepper any longer...