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

I've just looked up the specs for my Denford Triac Miller (1986
vintage)to give you an idea of a 'professional' setup so here they
are:-

X Travel 300mm
Y Travel 180mm
Z Travel 235mm

All travels are by Ballscrew of 16mm diameter x 5mm pitch

Maximum feedrate on all axes is 1000mm per min

Stepper Motors are 200 Steps/Rev 3.1 Amps 2.9 Volts

I think the motors are size 34 but can't be sure of that, whatever,
they are plenty powerful and work faultlessly, moving the workhead,
which slides on a dovetail vertical column, up at full speed without
problem (no moveable quill here).

Spindle is driven by a 1/2hp 3 phase motor through a Frequency
Inverter from a 1 phase supply.


I'm sure you can better these figures using modern components

All the best, Martin.