Strasbaugh Mechanical Maintenance Procedures
Version 1.2 - April 18, 1996 7 - 15
small steel plate on the wheel. This steel plate provides a
mounting surface for a magnetic indicator base. Mount a dial
indicator to measure the chuck surface as the indicator is swept
side to side.
The Y-Z plane adjustment consists of four clamp screws and two
jack screws. the clamp screws hold the spindle casting in position.
The jack screws push against either side of a vertical lever arm
attached to the spindle casting. Loosen the four clamp screws just
enough to allow adjustment. Loosen the jam nut on each of the
jack screws and rotate the jack screws alternately to push the lever
arm in the desired direction. While sweeping the indicator across
the chuck the dial should indicate the same deflection at both
edges of the chuck.
Once the spindle angle is adjusted to this position tighten the jack
screw jam nuts and the four clamp screws. Verify the alignment
after all screws are tight and repeat if necessary.
Misalignment in the X-Z plane will cause the wheels to grind a
spherical surface and will produce a convex or concave surface on
the chuck. This in turn will produce a nonparallel wafer from
outside edge to center. For this reason the X-Z plane alignment is
most critical.
Using a micrometer or the measurement probe on the machine
measure the thickness of a ground wafer at the center and near
the edge. If these readings are not within the specified parallelism
tolerance then an X-Z alignment is required.
The preferred method for measuring chuck flatness is with a
spherometer (spherometers are available from the manufacturer).
After grinding the chuck measure the surface with a calibrated
spherometer. A positive deflection of the spherometer indicates a
convex surface; negative deflection indicates concave. Once the
deflection is measured the alignment can be made to reduce the
error.
The forward foot of the spindle upright casting that supports the
grind spindle is fastened to a grind bed weldment crossmember.
This crossmember has a milled relief section running its entire
length which permits the steel to flex slightly. This provides a pivot
point for the upright alignment. The rear foot of the upright is
secured by a nut plate secured to the casting. A differential screw
runs through this nut plate and a threaded hole in the top of the
grind bed. The differential screw has a different thread pitch for the
nut plate and threaded hole. As the screw is rotated the distance
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