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Some dialogue on Gerber files 274X etc.

Question asked by JERRY_MARKETOS on Mar 6, 2006
I often learn things while working a support query...
Perhaps some of the knowledge I recently gained on Gerber files
will be of interest to others.

Gerber files are one format commonly used for capturing
what's contained on the layers in a layout and transporting
it among different programs, PCB vendors etc.  Genesys can
write from / read to its LAYOUT module in Gerber format,
among others.

Often among the first things learned about Gerber files is that
there exists an older format 274D and a newer format 274X
which embeds the apertures so there's no need for a separate
aperture list.  (It's usually preferred to work with 274X in modern day).

A misconception that can arise is "If it's 274X, then the Gerber file
must contain apertures".  Reason why that statement isn't always
true is because there are two main ways in which the information in
a Gerber file can be described, and only one of those ways uses
apertures.  The other method uses a "connect the dots" description
which identifies the layout entity(ies) as polygons and defines their
outer boundaries.

There is much information about Gerber files available on the web.
I found one site which contains a couple of excellent app notes
that provide good brief icebreaking.  artwork.com
http://www.artwork.com/gerber/index.htm
(see app notes at bottom of web page)  

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