Re: [CAD_CAM_EDM_DRO] Better resolution accuracy?

Dave Fisher wrote:

>I have a very heavy duty x y table fitted with DC servo motors etc which I
>am in the process of converting to a CNC router / miller.
>
>The 1" thick leadscrews are fairly coarse pitch, but all is very well and precision made.
>The current encoders (400 steps per rev) give me an effective resolution
> of 500 steps per inch of movement which I feel may not be good enough for
>routing curves etc ?.
>
>Not wishing to replace the leadscrews or encoders at this stage, I figure
>I could increase the resolution by putting a 4-1 reduction system via toothed belts
>and pulleys in between the motor shaft and the leadscrew end.
>
>Can anyone in the group offer any info / downsides to doing this ?
>
>

The belt reduction will lower your speed. Depending on the motors and
drivers,
that may be a problem, or it may actually make the whole system work better.
In many cases, smaller servo motors are made to run fast, into the
several thousand
RPM range, and so using a reduction provides a much better match between the
motor and the machine.

Yes, if you want smooth circular interpolation, 500 counts/inch is way
too coarse.
I'm running 20,000 count/inch on X and Y in my servo-eqipped Bridgeport,
and 40,000 counts/inch on the Z axis.

Make sure the belt is capable of handling the motor's torque. I used 3/8"
wide belts in mine, and they are really too narrow, but it works OK.

Jon