Homebrew PCBs

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