Strasbaugh Pneumatic Adjustments
Version 1.2 - April 18, 1996 9 - 7
VACUUM SWITCH ADJUSTMENT
Vacuum switches are installed in the system to test vacuum levels
on vacuum chucks for reliable wafer transfer. Accurate trip level
setting is critical for machine operation. Vacuum switches should
require infrequent attention if properly adjusted.
It should be noted that on all present and subsequent software
versions the vacuum switch for the work chuck is ignored.
Therefore, no adjustment or replacement of the work chuck
vacuum switch should ever be required.
A test apparatus for checking vacuum switch settings should be
assembled and retained for machine maintenance. The test
apparatus should have the necessary tubing and fittings to tee a
needle valve and vacuum gauge into the vacuum tube connection
at the switch. The needle valve should be teed into the tubing on
one end and left open to atmosphere on the other end.
With the test apparatus connected to the vacuum switch turn on
the chuck vacuum corresponding to that switch. To turn on
vacuum connect the positive lead of the solenoid coil for the
vacuum valve to +24 VDC (wire 21) with a clip lead. Place a wafer
on the chuck to measure the vacuum level at the switch. The
vacuum gauge will indicate the vacuum level under typical
conditions (make sure the needle valve is closed).
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