Homebrew PCBs

If you read all my posts you would see that I've done all that except 
the etching . Threads are so difficult to follow in these groups. Why 
etch when you can just use the artwork on paper and tape it to a 
piece of board. Don't waste time etching anything during the 
calibration phase.

--- In Homebrew_PCBs@yahoogroups.com, David McNab <david@r...> wrote:
> Don't know if it's a known problem, but something you could try is 
to:
>  - print out a test pattern
>  - etch it to a pcb
>  - program it to your cnc rig.
> 
> Then:
>  - stick a scriber bit into the cnc rig
>  - start the drilling run
>  - measure the errors in both directions
>  - convert these errors to x and y percentages
> 
> With this info, you'll have two different options:
>  1) transform the artwork prior to printing, so it
>     matches the CNC
>  2) transform the values in the drill file, prior to
>     submitting it to the CNC rig, so the drilling
>     matches the artwork.
> 
> Given that I'm comfortable with python scripting, I'd go for option 
1,
> and write a python/PIL script to transform the artwork.
> 
> 
> derekhawkins wrote:
> > Hi,
> > 
> > Just finished putting together a CNC drilling machine and have 
now 
> > stumbled on a problem that I never anticipated....The drilling 
machine 
> > appears to be more accurate than the printer used for the PCB 
> > artwork....Tried both a HP2420 (laser) and Epson 2200 (Inkjet) 
and the 
> > results were similar. Is this a known issue with CNC setups?
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > Be sure to visit the group home and check for new Links, Files, 
and Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> > 
> > If Files or Photos are running short of space, post them here:
> > http://groups.yahoo.com/group/Homebrew_PCBs_Archives/ 
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> > 
> > 
> > 
> 
> -- 
> Cheers
> David