Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
> On Mon, 13 Jun 2005 17:39:15 +0200, derekhawkins 
<derekhawkins@y...>  
> 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?
> 
> 
> yes, this is a known issue. lasers have all kinds of distortions.
> You can fight it by using non-shrinking media (in case of the 
laser), and  
> separate correction factors for x and y axis.
> If your PCB software does not support correction factors make a 
picture  
> and resize it with irfanview (www.irfanview.com).
> 
> I got my printer to produce a toner transfer that had non-
measurable  
> distortion only, so that should be possible.
> 
> 
> ST

I'm only using artwork printed on paper at this point. If it cannot 
drill that properly then it's pointless trying with an actual board. 
Already using scaling factors of 1.002 for the X axis and .999 for 
the Y axis. For a 6" X 4" matrix of 1/4" spaced holes printed at top-
center using the laser it does better than I could ever hope to drill 
manually but for a 9" X 7" matrix there seems to be skewing (greater 
than 10 thou) at one of the outer edges. Scaling can't help in that 
case. So you think it's fuser heat causing it? But the injet isn't 
much better either even though its errors are elsewhere.

BTW, a word of advice....Forget the toner transfer method.