Hi,
Does this indicate what type of servo it is?
Your description of the measurements you have made and the testing you have done confirm the motor you have as
common garden variety stepper motors. They are not servos.
A servo is an electric motor, it could be a synchronous motor (aka an AC servo), it might be a brushed DC motor, or
it could be a variable reluctance motor, of which a stepper motor is a particular example, coupled and mounted
with an encoder/resolver to indicate angular position. A controller, be it Mach4 in combination with an analogue motion
controller like the Hicon or a dedicated servo drive will drive the motor in direction and speed such that it angular
position (encoder) is exactly the same as is commanded by the trajectory planner (Mach4).
The controller/drive is said to 'close the feedback loop' and it gives a very crisp and accurate response to commanded position.
A stepper motor and its associated drive just steps a certain number of steps in a given direction. If the load is such that it
'misses or can't make a step' then the controller has no way to detect that fact. Thus if a two phase (normal) step motor is
commanded to rotate one revolution by the application of 200 pulses but it makes only 198 steps because it didn't have
the torque to make those last two steps it will end up at 356.4 degrees not 360 degrees as intended. Because a stepper is
'open loop' this inaccuracy will not be corrected.
This might sound like a disaster, but really its not. Provided your steppers are adequately sized and you do not ask more of them
than they are capable they will never miss a step and be accurate all day long. This is how the majority of hobby CNCs work.
There are a number of Chinese manufacturers making 'closed loop steppers' by incorporating an encoder onto a stepper motor
and a smart stepper drive. They claim they are as good as servos.....they're bull*********ting, they are good but still not a patch
on a real feedback servo. They do a good job of selling to hobby CNCers who are paranoid about losing steps.
What drivers, if any, do you have for your stepper motors?
If you don't have any the US company Gecko make superb and robust drivers, all their leading models are 80V capable.
They aren't cheap. Leadshine AM822s are 80V capable up to 8.2A and are more reasonably priced. In order to make your
stepper go fast use the highest voltage your driver can handle. The Gecko and Leadshine 80V drivers will make any stepper
sing.
Craig