RE: [CAD_CAM_EDM_DRO] Stepper motor position control

>A step is normally something like 1.7 degrees,
>but depending on the controller they can be made
>to microstep, i.e. have steps within this 1.7
>degree angle, but they will losse the micro
>position is power is lost, and if the load or
>acceleration are too hi they can miss complete
>steps. Normally they work blind, so you feed
>steps to them and hope they don't loose any,
>there is not normally an encoder to feedback any
>error. They also have issues of resonance at some frequencies of operation.

Just as a technical correction, the steppers come
in a variety of step sizes with 0.9, 1.8 and 7.5
degree steps (and multiples) being most
common. The 1.8º 200 PPR (Pulse Per Revolution)
variant is most common in hobby systems.

There are techniques to reduce resonance effects
other than microstepping, harmonic dampeners
(either a rubber mounted mass or a viscous
coupled mass connected to the motor shaft) is one good example.

David G. LeVine
Nashua, NH 03060