[Grayme]

I have an old milling machine with some dc permanent magnet servo motors on it. I'm going to build a cnc plasma/router. Is it worth using the motors I have,or go ahead and buy nema 34 steppers? Thanks.

[Al_The_Man]

Servo's have the edge over steppers, but it depends also on the type of drives and if you intend using them, if you intend to use step/direction system , they may not be compatible.

[joeavaerage]

Hi,
reusing old servos can be a real battle, especially if you have to try to find matching drivers. Also in many cases the servo/drive is expecting the controller to close the position loop,
and that is certainly possible but does seriously reduce the range of controllers that you might otherwise have used.

If you really want the crisp performance and the speed that servo offer, and they offer considerably better performance than steppers, then I would recommend proper AC servos
by either Delta (Taiwanese brand made in China) or DMM (Canadian brand made in China), they perform well, great support and documentation and free set-up and tuning software,
at fair prices.

Craig

[Al_The_Man]

I have used BLDC motor versions, they can be made to perform equally as well as their AC counterpart.
But I assume yours are DC brushed, A lot depends on your controller, for e.g. there are a few options for using control where the loop is closed back to the control, rather than the drive, which IMO, is the better choice.
The Dynomotion/Kanalog forum here is one such option.
A lot depends on what control method you decide on as to whether the motors, or even the drives can be re-used.

[joeavaerage]

Hi Al,

have used BLDC motor versions, they can be made to perform equally as well as their AC counterpart.

I too have used DC servos, both brushed and BLDC and they can perform as well ans any AC servo.....but can you recommend them to someone whom is a 'servo newbie'?
Mixing and matching drives, and programming and tuning servos is somewhat of an art and for a newbie a very steep learning curve.
Despite having used them I tend to shy away from them (DC/BLDC) as I know that I can get as good and even better ,in some cases, performance at modest prices by buying AC servos
and matching drive and is a very VERY much simpler installation, setup and tune proposition.

Craig