Re: gEDA-user: Strange (laser) print defects

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Tuesday 18 March 2008, John Coppens wrote:
>Hi all.
>
>Though this evidently is not a software defect, I'm wondering if someone
>on the list knows the cause of this problem or experienced similar
>effects.
>
>I was testing another paper (touted by a local electronics magazine as
>'ideal') for my quick-and-dirty toner-transfer PCBs, and found a strange
>defect, hard to describe. (see: http://jcoppens.com/misc/laser1.jpg and
>http://jcoppens.com/misc/laser2.jpg )
>
>The right part of each pic is normal typewriter paper, the left one is
>on the new paper I'm testing. The faults are systematic:
>
>- The appear always on the same spot in the board, independent from where
>I print it on the sheet.
>
>- They never appear on the 'normal' paper.
>
>- Printer settings and source file is exactly the same, of course. (I did
>experiment with different settings, but no difference was noted on the
>printout).
>
>First feeling was that some particle on the paper surface 'exploded', and
>blew away the toner before it got fixated. But this shouldn't happen
>systematically on the same spot. Problems with the paper/toner
>transport? They should show on both printouts, shouldn't they?

One would certainly think so John.  You may be onto something with the "before 
its fixated" idea though,  This is a laser, and the heat to fuse (fixate the 
image) might be related to it.  What I think I would do is waste a couple 
sheets, but make the first run with the printer set at half density, the next 
one at 25% etc to see if it goes away.  I'm thinking there might be a liquid 
buildup there that would spatter away as the heat was applied to this much 
less porous medium, particularly if the heating effect at that point was 
coming in at an angle.  The transfer images appear to have plenty of toner, 
and reducing it via the density setting might at least prove the theory.  It 
appears to have density to spare in your scans.

If that has no effect, then I'm afraid I don't have any better clues other 
than to try another, different transfer medium.
>Ideas?
>John
>
>
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-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
sushi, n.:
	When that-which-may-still-be-alive is put on top of rice and
	strapped on with electrical tape.


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