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September 1997

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Subject:
From:
Lainie Loveless <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Tue, 30 Sep 1997 12:12:11 -0500
Content-Type:
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text/plain (67 lines)
> Could anyone advise how to measure the machine placement accuracy and
> repeatibility for the Pick and Place machine.

Hi Poh --
On a CS 3AV, this is how we do this:

1.  Get a real of 1210's (decent size for this test and cheap) and
     cover a board with double stick tape in the area where you'll be
     placing your test parts.

2.  Create a program with known coordinates (something along the lines of:
     R1    x=1       y=1      Theta=0         Tool=1
     R2    x=1.5    y=1.5    Theta=90       Tool=2
     R3    x=2       y=2       Theta=180     Tool=1

     ...and so on).  We place maybe 8-10 parts for each spindle.  Choose
     your fiducial (maybe lower left) as both you "Zero" and your "Skew."
     This will give a 0 skew angle for calibrating.

3.  If you have multiple heads, do one at a time.  If you have
     multiple spindles on a head (we have 2 on each), then do the
     following to ensure you are calibrating the correct spindle:
     For a real of 1210's, say you're using a .100 dia tip, and its name
     is T1.  Assign T1 to R1 and T2 to R2 (and so on).  T2 can be defined
     as a .XXX dia  tool, but put another .100 tool in its holder (if
     you're using 1210's, for example).  This way, you can control
     which tip places which part and use the same (one) real of parts.

4.  If you have a transfer option (to a conveyor or reflow, for
     example), disable this, so the finished board remains loaded in the
     machine (to help reduce the chance of disturbing the placed parts).

5.  After you run the program, go back and visually digitize the parts
    (find their centroid coordinates of the part, where you usually
    do the pads).

6.  Find the differences for each placed part between what you
     programmed and where it actually placed.

7.  Separate the deltas into groups corresponding to each spindle
     tested.  We have a spec of .004 as the widest margin of error
     (repeatability) and an average of +/- .002 (accuracy).  If our
     deltas  were above these values, we would either re-calibrate or
     adjust the offsets, as necessary, and then re-perform this test.

Hope this helps.  Tell me if any of this is unclear or does not
apply.

Regards,

Lainie Loveless
General Atronics Corp
Wyndmoor, PA
(215) 242-7336

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