Hi,
these are from Leadshines website.
There is a two phase open loop stepper 496oz.in.
A two phase closed loop stepper of the same size 496oz,in
A 400W servo.
Notice the two steppers start with the same high torque but lose it as they get faster. At 1500 rpm the closed loop stepper is about 1.2Nm and the open loop a little
less, maybe 1-1.1 Nm. So the open and closed loop steppers have very similar characteristics. Beyond 1000-1500 rpm they have lost that much torque that it is likely they
will stall. The closed loop stepper will try with additional steps in the pulse stream try to keep up but if the load is too great it cant do it.
The servo, a 400w unit from leadshine has about the same torque as the steppers at 1500 rpm, 1.27Nm to be precise, but maintain that torque right up to its rated speed
at 3000 rpm. Note how both the steppers outperform the servo at low speeds but the servo is way better when going fast.
While servos are good for the power output they are quite expensive, if you really have to go fast then you just have to pay. The steppers on the other hand are pretty good value.
Even with microstepping open loop steppers seldom achieve resolution of better than 400 steps per rev whereas the torque vectoring of the closed loop stepper allows much better,
maybe 2000 steps per rev, a definite win.
I found on EBay the open loop stepper for $70 and a AM882 driver for $80 or $150 for the open loop solution.
On Ebay the closed loop stepper and driver were $247, about $100 more than the open loop set.
Is there enough advantages in the closed loop set to be worth the extra?
Craig