Homebrew PCBs

Ok time to stop lurking and post something. I have built two cnc
drilling machines (so far). The first used drawer slides, a wood frame
and 1/4 20 all thread drive elements. It worked but was slow. I bought
a 24x24 xy table at a swap meet mounted it on a 4x6ft piece of plywood
and built a bridge over the top with aluminum angle. Mounted a air
pencil gringer on a little z axis. This can theoretically allow a 24"
sqaure board. In reality I don't do anything bigger than 6 by 8. Ok
here is the trick. First drill the board. I use dancam which is free.
There are many other ways and programs available to do this. Thats
just the one I started using and it still works for me. The second
trick is POSTSCRIPT!!! (Or ghostscript if you must) Almost all laser
printers are off a little in one direction or another. In postscript
you can scale the printout in both the x and y direction to make it
much more exact.For instance on one HP 4m+ I used to use the scale was
.995 in x and .998 in y. This made everything line up over the entire
6x8 board. So steps are Drill board, Make photomask or tt printout,
align to board , transfer image. This has worked very well for me.

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> 
> Hi,
> 
> I've thought maybe i might reconsider building a CNC just for
drilling,  
> but i worry that the laser printer and toner transfer distortions will  
> make it useless.
> So i have printed two 150mm x 150mm square boxes on two separate
sheets  
> with my HP IIID and compared the two. there is about 1mm distortion.
> Of course this is not acceptable for cnc drilling.
> 
> Now, i have the new printer already but still no toner so i don't
know how  
> bad the distortion will be with that one.
> 
> You see, i definitely will not build a CNC drill only to find it
useless  
> because of printer distortion.
> I will not change to inkjet because it does not produce toner
transfer,  
> and toner transfer saves me much more time and money than a CNC
drill ever  
> will.
> 
> So, does anyone here use CNC drilling and laser printouts? Or has
anybody  
> done more experimenting with laser printer distortion and which
models are  
> good? The lexmark M412 did only cost 17eur and the toner will cost
50+ so  
> i might still choose another printer.
> 
> thanks
> 
> ST