RE: [CAD_CAM_EDM_DRO] Re: Plasma table gear reduction

Do a google for "Servo versus Stepper", there was a graph that depicted the performance of each. It clearly shows that Servos perfom best at near max RPM and steppers perform best at hold and very low RPM. Servos need a transmission and Steppers do not. Operating a Servo in this manner (without transmission of torque) will result in very high current load and short life of the servo. It would be near stall current at all times. This is ok for an automobile starter however servos are not designed to tolerate continual spikes of current. In other words, keep lots of fuses on hand. If it was reliable at all, the heating alone would be an issue. One would need to have a pinion on each side of the gantry to prevent "racking". And these two pinions would need to be timed with one another via a long shaft pillow blocked to the bridge of the gantry then timing belted to each pinion on its ends. Belt the servo to this shaft with reductions.

Has anyone considered using one of the new 24 volt starters as a largish Servo by adding an encoder? Could probably run one at 30 volts and not harm it. Would be a bullet proof servo. Higher voltages at less amperage than its rating.


Ron

John Dammeyer <john.dammeyer@...> wrote:

Hi Dave,

Don't get caught into the Horse Power verses Torque mistakes. Your power never changes since HP is a calculated value based on
Torque (measurable) and RPM (also measurable). If you reduce the RPM with gear reduction, you gain torque and the HP drops ever so
slightly because of gearbox losses.

John Dammeyer

> But, with servos, since you are spinning the motors fast, you get a
> much higher power output due to the gear reduction. (multiplied
> torque)
>

> No wonder the list archive was not as helpful as it is with so many
> other things.
>
> Dave

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