Re: Smaller machine stepper motor speeds and resolution

--- In CAD_CAM_EDM_DRO@y..., Mark Taft <mark.taft@m...> wrote:

> HI everyone,
>
> I am converting a small mill to CNC and have been considering

stepper motor

> speed and resolution of the z feed.
>
> Its obviously a compromise using steppers, so you need to gear the

feed at a

> rate which is practical ( fast as possible) while not loosing

accuracy

> resolution or losing steps ( being under powered).
>
> I have studied the stepper motor specs for the smaller 34 and 23

sized

> motors.
> They seem to get most torque at about 900 - 1000 Hz..
>
> With a 200 step motor this works out at about 4-5 Rps (revs per

second) ,

>
> using a lead screw of 60 tpi and a 4 inch travel ( maximum) it

takes about

> 60 seconds.
>
> I am picking a 60 tpi screw for increased torque.
>
> My question is this, from experience , what is the maximum

practical feed

> rate for small motors and what sort of resolution should I aim

for ?

>
> 1/2 thou accuracy is ok for me !
>
>
> Cheers
>
> Mark

My Denford Miller is set like this:-
5mm pitch leadscrews for X,Y & Z axes, these are geared via small
timing belts to the stepper motors at a 2.5:1 ratio. Motors are 200
step per rev. This works out at 0.01mm per step (about 0.0004")
which you could halve in 400 step per rev if you wanted to.
All the best, Martin