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Subject: [Homebrew_PCBs] DLP Double Sided Update

From: Mark Lerman <mlerman@...>
Date: 2010-05-23

Well, I've done some tests trying it the easy way, and while it
SHOULD work, it doesn't, at least not consistently. The problem is
that both the carrier and the board are (obviously) much thicker than
paper, and when they hit the drum/transfer roller interface there is
a slight (and variable) delay as first the carrier and then the board
go through. There are also problems in the X axis because the carrier
"grabs" slightly when it hits the drum and has a tendency to get a
little out of parallel to the motion axis. In theory we could wait
till the pcb (or a "header" of equal thickness) is under the drum
before telling it to print. However, this may create problems in the
charging timing since the printer does not expect there to be a board
present at that time. The X axis problem could be handled with a
better and longer carrier guide, but too much friction would create
its own problems.

There is no reason that DLP can't do ds boards, but I'm far from sure
that the mechanics of your typical laser printer can be "bulked up"
enough mechanically to produce consistent results. Probably the best
way to do ds DLP would be to make a flatbed laser system, much as has
been done for inkjets. Print one side, put it in an oven to fix the
toner, flip it and print the other side.

This would also be the way to go for a commercial product - anyone
interested in collaborating?

Mark