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Most printers ( and copiers)) enlarge the output to 102% to prevent the edges from having a corona.
Try scaling back to 98% and check your measurements.
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] On Behalf Of Slavko Kocjancic
Sent: Monday, September 16, 2013 4:15 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: Imaging PCB with LED
...so to clean up the problem, and not to argue...
I can make small board with toner transfer metod. Fine traces aren't
problem.
I can make small board with sensitived board and printed transparency on
laser Fine traces aren't problem.
... But I have problem with accuarcy. If I draw rectangle 200mm x 200mm
and then print that and then measure that, the dimennsion is not right.
With few prints made with same settings I measure the side from 199.5mm
up to 201.3mm. I tested 3 printers I own, and LaserJet 1018 and 1020
works identicaly. The Brother HL2030 is little better (from 200mm to 201.1)
So If I pick some big SOIC or TQFP with side of 20mm the error is aprox
aprox 0.1mm. It's bare visible with naked eye. So no problem with that.
Then I pick some chip in DIL40. The last pin is aprox 0.4mm off the
hole. If holes are drilled oversized then package should fit, else wil NOT.
Now I have terminal blocks on the edge of board. I have 20 pins stacked
(200 mils) and in last pin the difference can be 1mm and it's not
possible to fit that component.
And other thing is that I drill with CNC. And of course if one side of
board is ok the other is not.
Why the print's isnt consistent I don't know.
For toner transfer (printing on paper) It can be humidity, but when
printing on plastic transparency I think the humidity can't be problem.
As image is more distorted in height I assume that it's printer
mechanics problem.
As I know that my CNC is way under 0.1mm precission It's logical for me
to try to use it as photoploter.
The process is slower but got accuracy. So If I need accuracy (large
board) I should go with photoploter style, for small board's the toner
transfer is better choice...
I know that my english isn't perfect, but think that majority of people
will understand me. ...ker ne govorim kitajsko.
Slavko.