Reply with QuoteThe stepper cannot equal the least input increment capability of a servo.
Al.
Servo vs Stepper
On a servo motor the encoder resolution can be divided by 360 to determine the degrees of movement in one mark, Is a stepper motor capable of movements as small as a servo with 2500 lines, with quadrature equal to 10,000 per revolution?
Thank You
The Farmer
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Re: Servo vs Stepper
The stepper cannot equal the least input increment capability of a servo.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Re: Servo vs Stepper
No.
It Depends.
A stepper is like a rubber string. It tries to do microsteps with ever increasing resolution, and ever decreasing torque.
At 10 microsteps, ie 2000 steps per rev, a stepper has about 12% of stall-torque available (iirc).
Thus, e.g. a 3Nm stepper (typical Nema 23) will have 0.3 Nm of torque for 1/2000 steps.
If the 0.3 Nm torque is sufficient, the stepper will make the move.
If not, the microstep has load on the motor shaft, but it does not move, usually due to mass, friction and stiction (or mechanical load like an end mill against a workpiece).
Its not a linear relationship. Sine of angle, maybe, dont remember.
In practice, steppers are accurate to about 1/2 step (1/4 step on better systems NOT directly driven).
In practice, servos are accurate to about 1 step, or 2 steps, typically 1/2500 (5000 count encoder) or 1/5.000 (10.000 count encoder).
In practice, servos are about
5x more accurate,
accelerate 5x faster, and
run at 3000 rpm vs 500-700 rpm, ie == 6x faster.
You dont want to run your screw at 3000 rpm.
Heavy wear, and impacts, low lifespan.
Practically, run ballscrews at 1000 rpm or so.
Heres a link to the maths.
Microstepping: Myths and Realities | MICROMO
Re: Servo vs Stepper
On Automation Direct web site, they have stepper motor and Micro Stepping drive. The literature lists that it can be programmed to 51,200 steps per revolution. Is this actual movement or theory?
I want to build and affordable 2 axis pipe beveling machine to cut a saddle in the end of a 2-1/2" up to 4" pipe to construct a pipe fence and build a nice cattle handling pen and system. It needs to be somewhat accurate, but this is not aerospace parts or a Swiss Watch. When you tell a rancher or a contract machine in the pickup Welder $10,000.00, They have to go to the hospital to have their jaw reset. By the time you add a small planetary gear box to a stepper it is looking like the small servo system might be the way to go.
Thank You
Farmers Machine.
