If the hardware for home indexing is not installed, Machine Variables in LT Chuck Home Offset (variable
10) and RT Chuck Home Offset (variable 11) should be set to 0.0, which is the default value. Setting these
variables without the indexing hardware installed will result in a “Rotational Home” Fault.
When the hardware is installed, the homing procedure will first locate the edge of the index pulse. After this
is complete, the chuck will rotate to an optional offset. Change the offset in fractions of a rotation, positive
or negative with positive numbers going counter clockwise. Use the Machine Variables in LT Chuck Home
Offset (variable 10) and RT Chuck Home Offset (variable 11) for the left and right chucks, respectively.
The spin chuck does not have an offset.
A “Rotational Home” fault can be caused if the sensor is not detected and any offset is requested (indicating
that hardware is installed) or if there was a problem positioning the servo to a requested position. Correct the
problem and do another “Home All” to clear the fault. The spin station must index and home correctly to
clear the fault. The work chucks, however can operate without the hardware by disconnecting the sensor and
setting the Machine Variables 10 and 11 to 0.0, as outlined above. On installation, the PC-DSP card must
have been loaded with the configuration that supports this function. Also, jumpers must be instaleed on the
PC-DSP card grounding the home input signals from the work and spin chucks.
Wheel Wear Detection
Wheel wear measurement and functionality has been expanded. The exact behavior is different if the machine
is set for grinding AlTiC and alternative materials (Machine Variable 82, ATC Grinder) or its default state,
silicon grinding. The conditions that are detected will be identical, but in the case of silicon grinding, the
operator information is presented as a warning, asking that maintenance be notified, but to continue grinding.
When the conditions are detected while grinding alternative materials, a strong message is presented to
change the wheel, the send cassettes are disabled and the turrets are locked to prevent additional material
being presented to the machine. The condition is cleared in both cases by changing the offending wheel.
Wheel wear is now checked every time material is ground on the right work chuck. Wheel wear
measurements only use the right probe and reference data. As in previous releases, the amount of wheel wear
is compared to the Machine Variables Coarse Wear Lim microns (variable 25) and Fine Wear Lim
microns (variable 35). If this amount is exceeded, a wear limit message is put on the screen. In the case of
AlTiC and alternative materials grinding, the send cassettes are disabled and the turrets are locked.
A new optional check is made, wheel wear per wafer. This is set with Machine Variables Coarse Max
Whl/Wafer (variable 26) and Fine Max Whl/Wafer (variable 36), with the default, 0.0, turning off the
check. Set the maximum amount of wheel wear per wafer allowed (microns) in these variables. The
comparison value is cleared every time the Main Menu is traversed. Therefore, the first wafer will provide a
“mark” for the current amount of wheel wear and subsequent wear (at the right chuck only) will be compared
to the last grind (or “polish”). ). If this amount is exceeded, a wear per wafer limit message is put on the
screen. In the case of AlTiC and alternative materials grinding, the send cassettes are disabled and the turrets
are locked.
Also, Wheel Wear is now reported via GEM. Variable ID number 139 is used to report Coarse Wheel Wear
and Variable ID number 140 is used to report Fine Wheel Wear. Because the numbers can be undefined, the
value of -1.0e6 is the value signifying an undefined response. An undefined response is usually due to the
wheel being unreferenced.
Dress Frequency
The entry “Dress Frequency” in the wheel dress recipes has been implemented. Setting this number to 0 will
disable the feature. The exact behavior is different if the machine is set for grinding AlTiC and alternative
materials (Machine Variable 82, ATC Grinder) or its default state, silicon grinding. On starting a machine
from being upgraded, this value should be actually entered for both the coarse and fine wheel recipes. This
will confirm the correct entry, reset the count and store the correct state in the recipe.
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