Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!agate!howland.reston.ans.net!vixen.cso.uiuc.edu!uwm.edu!fnnews.fnal.gov!att-in!cbnews!wrb
From: wrb@cbnews.cb.att.com (wallace.r.blackburn)
Subject: Re: CCNC verses laser printers
Organization: AT&T
Date: Thu, 24 Feb 1994 13:55:43 GMT
Message-ID: <CLqEoy.IAA@cbnews.cb.att.com>
References: <c3X8Hc6w165w@seanews.akita.com>
Lines: 46

In article <c3X8Hc6w165w@seanews.akita.com> dmauch@seanews.akita.com (Daniel R. Mauch) writes:
>I have concluded that a inexpensive laser printer and CCNC does work well 
>together. I have recently run about 20 small boards off drilling them 
>with my Cheap Computer Numerical Control drill machine. The quality of 
>the drill pattern was excellent however when I overlayed a transparency 
>over the hole pattern I noted that the pads were off by up to .020. I 
>subsequently verified that the CCNC machined drilled the holes without 
>errors. I just drilled two boards that had 202 holes each and decided to 
>overlay a photoplot to see the difference. WOOOOOW! The pads and the 
>traces lined up to within .005". I also firmly believe that It was my 
>inability to properly match up the photoplot with the drilled holes that 
>induced the error. SO I think that perhpas drilling the boards first is 
>not the way to go. In the next few days I will etch a board first then 
>drill the holes.
>        Since my equipment is very good, I cannot visualize how it would 
>even be practical to combimne CNC with a plain paper copier for use with 
>a toner transfer system.
>
>-- 
>[] SEANEWS [] Seattle Public Access Usenet News + Mail [] +1 206 614 0048 []
>dmauch@seanews.akita.com

I think it depends on the local equipment too.  We have a Ricoh copier here
at work that appears to have very good accuarcy in both size and xy ratio.
Our industrial-strength QMS laser is off a touch though.  I've solved the
problem by using the correction factors in Traxplot (as per your advice
Dan).  I've had good results both drilling before and drilling after using
the PnP Blue.

I am using the Kepro negative method now.  WOW!  This makes BEAUTIFUL
boards!  Drilling first seems to be easiest here because it is easy to
overlay a negative on the drilled board since you can see where the holes
are easily.  I got a negative shot at a local print shop.  They charge $10
for an 8.5x11.  I did a paste-up of three differnet patterns on one sheet
to get the most negatives for my money.

The big hassle to drilling after etching is lining the board up square.  I
add a guide hole at 0,0 and my CNC software let's you "home" it before
drilling, so that's no problem.  But it has to be square.  That means I
have to get the image on the board square, the board itself has to be
square, etc.
-- 
   Wally Blackburn		   Clinton-Gore - Socialist Leadership
   wrb@ccsitn.att.com			          for the 90s!
   Amateur Radio Station AA8DX	   I'm the NRA.
      *More people have died in Ted Kennedy's car than from my gun!*
