Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi Derek,

On 9/9/06, derekhawkins <eldata@...> wrote:
> >The secret is to ensure that you always approach the location from
> >the same side of the backlash.
>
> How do you do that for both X and Y axes?

Assume you're starting at the origin (bottom left).

Advance Y to the hole with the lowest Y value.
Advance X to the hole. You can continue advancing X for values with the same Y.
Advance to the next Y value. If you are to the right of the lowest X
value, you need to backup past the X value by more than the backlash
amount and then advance to the X.

Another way of looking at it on a move-by-move basis

if desired-Y < current-Y
move to desired-Y minus largest Y-backlash amount
move to desired-Y

if desired-X < current-X
move to desired-X minus largest X-backlash amount
move to desired-X

Using the above guarantees that you're always approaching each hole
from the same side of the backlash.

If you figure that your backlash was 0.008, then I'd probably use a
largest backlash amount of 0.020 to be safe.

Many CNC programs support backlash compensation, which requires
entering a faily accurate backlash amount. The accurate backlash
amount is only needed for milling. For drilling, you can use a larger
value than the actual backlash.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/