David,
Can I make a stab at this?
First, though, what is the thickness of the PCB you mention?
Often, I do the following to locate, and re-locate when necessary,
work pieces atop the mill table:
In the CAM drawing (I import CAD .DXF drawing into CAM software for
G-code processing), I'll draw a bounding box around the work piece (in
this case, using the PCB's actual size) so that when this box is cut
and removed, the PCB drops into the vacated space. For me, this has
been a dead-on, precise fit -- absolutely no wiggle room (initially, I
was surprised at how tight this fit actually was).
From this point, since the bounding box is part of the coordinate
system used to position the cutter/drill, after touching off the Z
axis (at zero), you're good to go.
This has always worked extremely well, too, when a workpiece has to be
repositioned, for example, to mill on the reverse side of the workpiece.
I often use mill tabel double-sided tape to fixture pieces in place.
Johnson Plastics (
http://www.johnsonplastics.com/), for instance, has
3/4" wide double-sided tape that is sticky, sticky, sticky. . . .
Hope I accurately caught the drift of your post and this information
is relevant.
-Brian
Brian Chapman
Evansdale, Iowa
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