Homebrew PCBs

On Wed, 16 Nov 2005 20:47:47 +0100, Alan King <alan@...> wrote:

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> "Many will find that TT combined with CNC drilling is a bad
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> combination. (Assuming the CNC is of decent accuracy<G>)"
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> Ballendo
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> Of course, this was more than a bit off.  Takes 3 minutes of 10th grade  
> geometry to fix axis scaling errors.  Anyone not able to  use the
> relative accuracy of both and scale for absolute accuracy in 15 minutes  
> should really turn their high school diploma back in, they
> should've flunked the math requirements.


I found you must first adjust your printer properly, then make a trial  
transfer which you measure, and then simply compensate.
The thing is, if the printer isn't aligned horizontally and vertically you  
usually will have some amount of skew or trapezoid distortions, which is  
hard to compensate. Once it's aligned properly (see service manual, on the  
web for many printers) you have only linear error in x and y which is  
easily compensated for.

This way i got it down to no measurable deviation easily.
Also, while inkjets are often more accurate, you still need a true print  
just the same with photoprocess.

If you have any shrinkage while transferring from the heat simply run the  
paper through the laminator before printing, to dry it properly, then it  
won't shrink any more.

I readily admit i didn't master the photoprocess, but i also now make  
great boards (with legend by the way), much faster, cheaper, and easier  
than i ever did with photoprocess. Even if i mastered it i would need  
considerably more gear, effort, and cost than i do now for TT.
For photoprocess you _need_ sensitized boards (or you have to add the step  
of sensitizing which is again not that easy). They are much more expensive  
than the cheap blank offcuts i get. You _need_  a lightbox to do it  
properly, not necessarily expensive, but surely comparable in building  
effort to a fuser. You _need_ either a inkjet or special (expensive) laser  
paper, i don't have an inkjet and don't want to keep one ever again. You  
need to develop them, which means another step making mess and effort and  
chemicals.

When i make TT i don't need all that. I plug in the fuser to heat up,  
meanwhile go and cutoff and clean a suitable PCB, and print the layout. 3  
minutes max.. Then i cut the layout out, put it on the pcb, feed it  
through the fuser - another minute max.. When it's out i scratch the paper  
with a wirebrush i keep in a desk drawer, and submerge in water (the brush  
rips open the paper and allows water in quicker. Do not brush too much or  
it'll go through and damage the transfer). After a moment in water i take  
it out, hold it over the dustbin, and "roll" the paper off with my thumb  
starting at the center. submerge again to wet it and rub off the rest.  
Submerge again to flush off any paper remains and put in the etcher. two  
minutes max.
That's 6 minutes, and i have have estimated very generously - i'll time it  
next time i make a board.

Did you notice there's NOTHING to prepare or put away? All waste lands in  
the dustbin already. I don't have a sink in the shop so the container with  
the water is filled and emptied when i go by one anyway.

I don't think you can make a photoprocess in the same time, and if it  
surely requires more space to leave all the gear prepared.

But what am i doing, wasting my time here. Let them believe what they want  
i have work to do.

ST