Re: [CAD_CAM_EDM_DRO] CNC Precision on a Sherline

mszollar wrote:

> Question; I was calibrating my Sherline mill motor travel/backlash,
> etc for my CNC machine. When I was through I noticed that I needed
> 8080 steps per inch (x and y) and 7950 SPI for Z. Is the axis screw
> that inaccurate?
>
> I measured with a micrometer and a dial indicator; both show the
> same results.

Are you sure you counteracted backlash in these measurements? This much
error would easily be accounted for by backlash. You need to make the moves
in the same direction both at the beginning and end of the move to
prevent the backlash from reducing the actual movement.

So, you can't just move left to zero on the indicator, then move right to 1.000"
and count steps. You need to move left PAST zero, then move right to get to
zero, then continue right to 1.000". Then, you will get an accurate reading
of screw pitch. By moving left until the dial moves, then moving right
until the dial starts to move the opposite direction, you will get a reading of
the backlash.

Jon