Homebrew PCBs

Robert Hedan wrote:

> I've got my eye on them also.
> 
> If you check the chart, the price is the same for 10 day lead time as well;
> 50% reduction in waiting.  7 day is only $20 more, it's at 5 days that it
> starts getting much more expensive.
> 
> I used the same technique selecting CPUs for my new PCs; start at the
> bottom, and work my way up until I hit a big price hike, then I take the CPU
> just before the hike.
> 
> I have 3 SP57B steppers waiting on the shelf.  I've got an assortment of
> threaded rods from 3/8" up to 1/2" with 2" long nuts.  I was planning on
> fixing 2 of these long nuts onto the slides and passing the threaded rod
> through.  By using 2 nuts, I get most of the play out.
> 
> I'd love to see pics on DIY CNC drilling stations.  I've got most of the
> stuff figured out now, I just need to plug a few holes in my design.  One
> last place I have to go see is a local ball bearing shop to get several
> units of various sizes.
> 
> Then I have to address alignment; how to get it all perfect (or close to).
> Even making a flat surface is not that easy when you talk 1/1000s of an
> inch.  Adding a gantry and the sliding motor platform is more variables.  I
> really want to make one, but I'm not making it unless I can address
> alignment properly.  I might as well use my small vertical drill if my CNC
> station is not aligned right.
> 
> Robert
> :)
> 
> 
> -----Message d'origine-----
> De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
> la part de Alan King
> Envoy\ufffd : mai 29 2005 21:01
> \ufffd : Homebrew_PCBs@yahoogroups.com
> Objet : Re: RE : [Homebrew_PCBs] Re: Minor production run?
> 
> 

   Yep of course, I do the same, actually saw it before I mailed just forgot to 
go back and edit it for the lead time for best value..  Thought I did, sometimes 
I think mozilla doesn't keep all the edits or something.  But got looking and 
pricing other things as well, mask etc.  May have forgot to do the edit..


   I just used plain 1/4-20, it's fine for light duty.  A driller doesn't need 
CNC heft.  Mine has tons of play if I put pressure on it etc, but as long as 
it's aligned correctly and centers itself in the play it'll still work great.  I 
don't even worry about the backlash much, easy to approach from the same side 
for a drilling program.

   And look for ball bearings on Ebay.  I got a pack of 50 precision for like 
$20.  Smaller skate sizes like that are cheap even for precision.  Might have to 
cut down your rods to fit etc, but they'd work.



   Remember, alignment, precision, absolute precision, and play are all seperate 
things.  Alignment is the only one that is critical.  End to end relative 
precision isn't that critical, you can interpolate.  Absolute precision isn't 
that critical, you'll be having to align to the board somehow anyway, fixed 
alignments rarely work well with boards.

   Vertical alignment is the only one really critical, so you don't break bits. 
  About everything else is pretty loose, anything you do will be good enough for 
the most part.  You could even make it way out of square on purpose, and still 
map it back to working great.  Drill depth isn't critical etc.  X and Y have to 
be relatively accurate for a single run, but not absolutely so, you can easily 
calculate where you should be after locating 3 points actual position.  A 
machine necessary to do good drilling is way less precision than some .0001" 
absolutely square in every dimension monster mill, some people just are using 
software that can't do simple remapping so that's how they see it.

Alan