Re: [CAD_CAM_EDM_DRO] CNC controller backlash question

Tim Goldstein wrote:

>Having different amounts of backlash in opposite directions just does not
>make any sense to me. It can differ at varying points along your movement,
>but I think it has to be the same in both directions at any given point.
>Here is a brief write up I have on my site:
>
>

Yes, I mostly agree with this. It is possible with BADLY worn screws
and nuts to
have all the backlash be taken up in one direction immediately, but part
of the backlash
is taken up during the actual move in the other direction, AFTER the
slide begins to move.
But, this requires the screw and nut to be horribly worn, with threads
that resemble a
sawtooth rather than a proper screw form.

A worse problem is differential wear on the screw, where you get
different amounts
of backlash when the machine is in different postitions. Usually, the
middle of the
screw is much more worn than the ends. this leads to pitch errors as well.

Jon