Homebrew PCBs

On the few double sided TT I have done, I put registration marks well 
off the board edges and line up the two pages on those first.  then 
slip the board between.

The registration is so close that the annular rings on both sides are 
fully formed.   The drill holes are often not as precise.  the 
registraton is withing a few mils.   

HP-LJ-4 is what I have used.

One of the unknowns about copiers and printers is that they are not 
really 1:1 in both X and Y.  When you flip your board and re-print, 
the board would be in the same top of sheet orientatation.  if you 
flipped AND rotated 90 degrees, your alignement would be worse.


Dave




--- In Homebrew_PCBs@yahoogroups.com, "Dave Hylands" <dhylands@b...> 
wrote:
> The real problem with laser printers and backup is that the paper
> physically changes size between printing the front and back side. 
This
> is especially true in high-humidity areas (like here on the Wet 
Coast
> :).
> 
> I've measured 1/8" shrinkage. If you run the paper through once 
(and say
> print something off in a corner), you get MUCH less front-back
> misregistration.
> 
> I was a Principal Software Developer at Creo (they manufacture
> Computer-to-plate imagers for the printing industry), and one of the
> products I was involved with was called Digital Blueline. This is
> proofing software for doing backup proofs. We had the ability to 
shift
> the back page to optimize alignment with the front page, and once 
the
> paper was dehumidified, backup was pretty good.
> 
> So having said all that, I don't see any problem getting backup on a
> media which doesn't change size, espcially if you have the ability 
to
> apply an external shift. 
> 
> Doing backup with an inkjet should be MUCH easier.
> 
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
> 
> > -----Original Message-----
> > From: ballendo [mailto:ballendo@y...] 
> > Sent: Thursday, April 29, 2004 2:31 AM
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: [Homebrew_PCBs] Re:laser jet consistency and registration
> > 
> > 
> > Hello,
> > 
> > In a previous life I was a copier service tech. Prior to laser 
> > printers, but as most know now photocopiers use the same process.
> > 
> > We used to have a heck of a time with page registration, and I 
know 
> > the truth of Russell's comments below having adjusted many optics 
> > sets to<wards> 1:1...
> > 
> > So I'm wondering, Has anyone taken the time to see if he or she 
can 
> > get a good back to back registration on PAPER?
> > 
> > Because if you can't get the sheet of paper to reliably go 
through 
> > twice accurately; isn't it kinda unlikely that the mods to allow 
a 
> > board to go through are gonna improve things?
> > 
> > Next, IF it is possible and likely for the registration of two 
passes 
> > to line up with respect to the board edges: Has anyone held this 
up 
> > to a light and checked if all the holes line up all across the 
board?
> > 
> > For a eurocard sized board?
> > 
> > Thank you in advance,
> > 
> > Ballendo
> > 
> > P.S. I was really getting gung ho about direct etch resist 
> > printing-- even posted awhile back about the CD tray printer 
> > I saw at Fry's, and 
> > was talking to avecia about their resist and soldermask, when...
> > 
> > The above questions popped into my head. For me, if ya can't 
> > do two- sided, it's a no-starter. SMD and SMT are not going 
> > away, and they 
> > require two-sided layouts more often than not (means always<G>)
> > 
> > I truly LOVE the idea. And with a print head on a cnc machine the 
> > registration problems go away... For others to take their place<G>
> > 
> > But if I'm gonna have to TT the second side anyways...
> > 
> > 
> > In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@n...> 
wrote:
> > > The similar interests are to achieve the *end* result. I'd 
> > rather see 
> > > CNC discussions here than boring old laser printer crap 
> > which i know 
> > > is inconsistant between models and toner brands anyway.
> > 
> > 
> > 
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