Metric CAM (excellon/gerber) files

Andy Warner wrote on Mon, 05 January 2009 12:37

I am designing a metric board, can I generate cam files that are also

metric, if so how ?

What units you used to size the board and define the packages on that board

have nothing to do with how the resulting information is written to Gerber

files.  Most boards require a mix of units for various parts anyway.

Quote:

It seems that the excellon and gerb274x cam files generate inch-based

outputs. Do board houses even accept metric cam files ?

 

If conversion to inches is not necessary, I would like to avoid it, for

all the obvious reasons.

There is no "conversion" to worry about since how you got to the

measurements has nothing to do with how they are written to CAM files.  And

no, your objection is not obvious at all.  I would leave the defaults

alone.  Board houses know how to interpret these files.  I wouldn't send a

board house a metric Gerber file unless they specifically told me they can

handle it.  No board house is going to misinterpret a inch file.  I'd be

more worried that their process assumes inch files and therefore

misinterpret metric ones.

Keep in mind that inside Eagle it's really neither inches nor mm.  If I

remember right, they use integers of some very small unit.  But all that

doesn't matter.  The computer will convert.  Computers are good at that

sort of thing.

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Olin wrote on Tue, 02 March 2010 22:07

There is no "conversion" to worry about since how you got to the

measurements has nothing to do with how they are written to CAM files.

And no, your objection is not obvious at all.  I would leave the defaults

alone.  Board houses know how to interpret these files.  I wouldn't send

a board house a metric Gerber file unless they specifically told me they

can handle it.  No board house is going to misinterpret a inch file.  I'd

be more worried that their process assumes inch files and therefore

misinterpret metric ones.

Maybe he read Olimex's FAQ which says:

Quote:

Q: I designed my board in Inch (mm) units, in which units should I

export my Gerbers?

A: Always export your gerbers in the units you designed board to

prevent rounding errors in your Gerber generation due to the unit

conversion.

which would make it obvious to not want to make gerbers in inch when the

board is made in mm. But, what do I know...

Stig

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Maybe this doc is of relevance to your Q

http://www.artwork.com/gerber/274x/rs274xrevd_e.pdf

Table 1, page 9 shows there are codes to select inch or mm units. Eagle's

CAM processor does inch all the time afaik.

Maybe this doc is of relevance to your Q

http://www.artwork.com/gerber/274x/rs274xrevd_e.pdf

Table 1, page 9 shows there are codes to select inch or mm units. Eagle's

CAM processor does inch all the time afaik.