Homebrew PCBs

Ed Okerson wrote:

> Alan King wrote:
> 
> 
>>some people just are using
>>software that can't do simple remapping so that's how they see it.
> 
> 
> What software do you use?
> 
> Ed

   It's my own.  Very simple comms and 3D line drawing/motion control in the PIC 
side, and a simple Qbasic program on the PC side doing all the math and telling 
it where to go.

   Locate a hole's actual positon by putting a small bit just over the board, 
then get it centered, then look from 90 degrees off and get it centered from 
that direction as well.  The program knows where that hole is supposed to be 
from the file, and where is really is from where you jogged the machine.  A 
second hole gets you a line, and also the actual distance between the holes. 
Use how far apart they are supposed to be vs really are to figure the error in 
scale, and use that to move to actual coordinates.  A third hole 90 deg off from 
one of those gets you the same distance and error for the other axis.  With 
three holes you can really work out misaligned rotation as well assuming the 
print is at least basically square.

   I know how and it's just as easy trig, but I've never bothered putting that 
part in.  Align one hole, move the motor in X, and slide rotate the board to 
align the other hole.  Then they're on the same Y in the program and reality, 
you have the rotation right, so from there it's just scaling and offsets of 
drill file vs machine coordinates.

   I don't use PC programming enough since I mostly do assembly on the 
microcontroller side of things, but it's a simple program so I should really 
rewrite it in C and flesh it out.  From this working point it was easy to add 
HPGL and do Corel Draw output, once I got that working I didn't go back to the 
comms and drilling program much.


   Main thing is I went to mostly surface mount.  A few jumpers is easier than 
messing with the drilling even if it takes a bit longer.  Heck you can do 2 
sided boards and vias without any drilling, simply bring traces to the edge of 
the board on top and bottom and shear it there and jumper around the edge.  It 
can do quite a bit if you lay out your board intending to use it from the start 
and put your crossovers near an edge.  Gotta mount a wire in the hole and solder 
both sides, may as well wrap a simple jumper around.

   I need to set the CNC back up and use it more, more for other things than 
drilling.  With a router bit it can do board cutting etc.  With a grinding wheel 
and a jig to hold the object to cut it can do some pretty neat stuff.  More 
useful is a simple 2 slide dremel with grinding wheel and a motor to move it. 
Unattended straight fiberglass cutting is the best kind with the dust.  Even 
with a plastic bag around it for the mess it's still quite noisy with a dremel. 
  Clamp it down, press the button, and go watch TV for a minute or grab a beer. 
  Hell end up watching the machine much of the time anyway, but at least you can 
get a good distance from the tool and save your ears.

Alan