Benefits of Belt Drives for Steppers

[Robin Hewitt]

I always use belt reductions to get 5um per half step, tuck the motors out of the way and keep the hand wheels. I round every movement out to 0.005mm. Works for me.
Thing is my latest mill conversion has steppers and DRO's. Not a problem unless the stepper controller can read the DRO's. I couldn't resist...
What will I have it do when the motor disagrees with the DRO by >0.01?

[David Child]

I always use belt reductions to get 5um per half step, tuck the motors out of the way and keep the hand wheels. I round every movement out to 0.005mm. Works for me.
Thing is my latest mill conversion has steppers and DRO's. Not a problem unless the stepper controller can read the DRO's. I couldn't resist...
What will I have it do when the motor disagrees with the DRO by >0.01?

I use similar figures with a lathe cross slide—5um per full step and 2.5um per half step to give 5um on diameter. I found that measuring with a 1/10 thou dial gauge (all I had that accurate) showed that a conventional stepper would give inconsistent half steps. I changed the stepper and controller to one with a 1000-count encoder, and the problem was solved. Incidentally, the drive is much quieter and smoother, and the controller is smaller and does not need fan cooling.
I'm a convert to feedback steppers but is it worth changing them on my Bridgeport?

[m_c]

I use similar figures with a lathe cross slide—5um per full step and 2.5um per half step to give 5um on diameter. I found that measuring with a 1/10 thou dial gauge (all I had that accurate) showed that a conventional stepper would give inconsistent half steps. I changed the stepper and controller to one with a 1000-count encoder, and the problem was solved. Incidentally, the drive is much quieter and smoother, and the controller is smaller and does not need fan cooling.
I'm a convert to feedback steppers but is it worth changing them on my Bridgeport?

The issue with microstepping, is that you're essentially relying on the energised coils to balance the rotor between steps, so any external forces can affect the actual position.
The reduced noise is down to a combination of modern drives switching above audible frequencies, and producing a more sine like output, so you don't the noticeable step pulses. Even if you run them in single step mode, they'll still likely be outputting a more sine like wave form, rather than the old stepper drivers, that simply stepped between voltages.

As for your Bridgeport, does it work well enough for you as it is?
Personally, for a Bridgeport if I was going to change the motors, I'd go for proper servos, as they'll still outperform any comparably sized closed loop stepper if geared properly.