Homebrew PCBs

Robert Hedan wrote:

> BINGO!  Thanks Alan!
> 
> I've been mulling over how to get a perfectly level platform and I think I
> have it.  If you look under the top of a small table saw, you'll see a sort
> of criss-cross reinforcement pattern in the alloy.  Duplicating this pattern
> into wood using a router (but with deeper cuts), placing a short retaining
> wall around the square and then filling that with liquid plastic, I should
> have a fairly sturdy and flat surface.


   But it's a bit easier to fill the space with hmm what,...  more wood! :)
Really flatness is simply not needed if your main purpose is drilling.  Just use 
a 1/2" piece of wood for a sacrificial plate and drill 1/8" or so extra.  How 
far extra you go doesn't matter much..

> 
> Gravity will take care of the hard work for me, perfectly flat surface.  I
> just have to sand 1/8" along the perimeter to remove that curve liquids do
> along vertical walls.

   Meniscus or similar is one of the words, can't recall if that covers both up 
and down or only one or is really the flat in the center, it's been a long time.

> 
> I can also use the same technique to make a perfectly flat side to the
> gantry and the vertical drill slide; 2 other areas that still puzzled me.
> Liquid plastic also has the advantage of strength with little weight and can
> be threaded.
> 
   You don't NEED 'flat', just aligned.  As long as your axes are aligned to 
each other properly, it won't matter if you are 1/16th inch off all over the 
place for 'flat', you'll still drill correctly.  You seem to be thinking from 
'everything should be perfect'.  You should always start from 'everything is 
totally screwed' and work up to 'this is the abolute minimum to get perfect 
results'.   You don't need half of what you're already talking about lol ..




> Shoot, there might even be a small market for this if I can make it
> straight.
> 
> Robert
> :)
> 


   Yeah, I have a few hundred steppers on hand.  I can also actually do the 
needed things too, have my own system and layout that can run 5 phase bipolar 
steppers and anything less.  Still hard to get too motivated, the market is 
relatively tiny.

   Use the straightness that is already in a $20 8 foot section of aluminum 
angle from Lowes, and forget about making some surface that is ultra flat, it's 
not needed.  Actually I really used a 'straightness' that is far better than 
that, I simply used two points as endpoints everywhere it was possible.  Nothing 
gets much more straight than that.  The 'straight' from the rails was only a 
starting point to use as a starting reference.  I need to write it up and take 
pictures, while always a bit time consuming to do the work it's really not that 
bad to build.

Alan