Re: [CAD_CAM_EDM_DRO] Is a reduction drive necessary for servo motors?

Peter Homann wrote:

>Hi,
>
>I'm looking at upgrading a CNC lathe that currently has 210 oz/in steppers
>to servo motors.
>
>The servo motors are rated at just over 300 oz/in.
>
>The current stepper set-up is direct coupled using zero backlash flexible
>couplers. The ball screws have a lead of 4mm/turn.
>
>As the servos appear to be more powerful than the steppers, I feel I should
>be able to do a direct replacement, but have not used servos before.
>
>Do I need to use any gear reduction, or can I direct couple the servos via
>the flexible coupling as is done with the existing steppers.
>
>

Servo motors generally produce the most power at higher speeds than stepper
motors. This is a very broad generalization, however. There are servo
motors optimized for low speed torque, and they are often used in direct
drive applications. Very small servo motors will likely need a belt
reduction,
as they have lots of speed, and not much torque. If your 300 Oz-In servo
rating is continuous, then you really have no problem, and should do fine
with direct drive. If the 300 Oz-In is a peak rating, then it is not
completely
clear. A stepper can produce something close to rated holding torque at
zero speed all day without harm. A servo can produce the continuous
torque rating all day, but can only produce the peak torque for some small
amount of time, such as 10 seconds out of every 10 minutes. So, if your
motor is rated for 300 Oz-In peak, you will need some reduction.

Jon