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May 1998

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From:
SteveZeva <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 8 May 1998 09:19:52 EDT
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Hi Ralph,

     At past employers where I've worked and used high-speed turret-style chip
shooters, there sometimes could be a problem with a nozzle where it wouldn't
be quite as smooth in it's action as it should be, or at some point during a
preventative maintenance of the machine, one of the 2 springs inside the
nozzle was either misshapen or stretched so that there was excessive force
being applied when picking and placing. We would experience the same thing
with glass diodes and sometimes capacitors.

Practically all turret-style pick and place machines have spring loaded pickup
nozzles that are very delicate and precise in their movement, and must be
maintained well to avoid these sort of problems. The earlier generation of
chip shooters that I've worked with (Fuji CP-II, CP-III) the X/Y table moved
only in the X/Y direction, as that style machine has matured (CP-IV, CP-VI),
it now moves in the Z direction according to programed part height.

     There's all sorts of ways to create too much force during pick and place.
One way is to not have to board supported correctly where it's bowed upward
past where the machine thinks the surface of the board is, so now it's
slamming the part on the board. Another way is by programming in too thin a
part height, it'll still pick and place the part, but you'll be compressing
the nozzle springs too much.

So if it's not happening at wave, that would be where I'd look...

-Steve Gregory-

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