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

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

>> I am going to drop off assembly kits at a manufacturer on Monday for a
>> board (and P&P files) made pcb. I will try to get some feedback from
>> them in terms of their set up process, how they want their files and
>> how they handle rotations. In this particular case components are only
>> on the top side, but I will enquire about bottom side components.
>
> Thanks. That will be useful information.
>

I had a chat to the manufacturer about orientation, rotation, offsets
and so forth (this was Elprom in Cape Town, South Africa,
http://www.elprom.de/e_home.html). They use Samsumg machines.

1) Rotation: different machines rotate in different directions (even
different Samsung models). Some rotate CW, others CCW, so they do a
fair amount of manual correction. When they set up they do a dummy run
using double sided tape and then check rotations and correct them.

2) Axis: they use an axis which has its zero point at the operator
(who stands on the right of the machine bed) and increases away from
the operator. i.e. bottom right is zero, x increase to the left and y
increase to the top. I suspect some manufacturers will use bottom left
as their zero. Take home point, check with your manufacturer.

3) Fiducials: they use the bottom right fiducial as their zero point.
They want the fiducials in the P&P files. There is no need to adjust
your files so that the fiducial is at zero, as they reference the
fiducial as zero, and the machine adjusts the values based on that
point.

4) They prefer separate top and bottom placement files.

5) They flip the board around the x-axis (i.e. in the y direction). If
you hold the board/panel in your hands and then flip it away from you,
that is what they do (left stays on left, right stays on right, side
closest to you is now furthest away from you).

6) They are an IPC member but they people I chatted to were not
familiar with IPC-2581.

I suspect most assembly houses are going to have their own particular
way of setting up boards. The most important thing to do is have a
discussion with your particular manufacturer before they go into
production of your boards. The other thing to note is that the
particular convention of your file is probably not a big issue. If
they can reference the components correctly (fiducial point in P&P
files) and have an accurate BOM to work from they will correct any
issues.

I've asked them to give me some feedback once they have assembled the boards.


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