Re: gEDA-user: Part Rotation in XY-data

["Duncan Drennan" <duncan.drennan@xxxxxxxxx>]

> I am worried about conventions. Are angles positive for CCW? To calculate
> angles on the bottom do you look through the board or flip the board?

I can't remember the angle/rotation convention on those machines. Will
check this on Monday.

The way we worked with the Samsung machines the rotations were
calculated as if looking at the side of the board you are going to
populate, i.e. *not* through the board.

> IPC-2581 references coordinates as positive x and positive y from a
> fiducial placed in the lower left corner on the top side of the board.
> Is this commonly accepted practice?

On the Samsung's you could choose your reference point as any point.
What they did was line up the machine placement crosshairs with a
point and then set that as the reference. Obviously choosing an easily
identifiable reference point (like a fiducial) makes it easier for the
machine operator. Not sure what commonly accepted practice is, so
provide docs which tell them where the reference point is.


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