Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 561)

Surface Grinding Fixed Cycles
Chapter 16
16-11
J - plunge pick amount at start.
The value entered here is an incremental value used to indicate the distance
that the plunge axis moves as soon as the reciprocating axis begins
decelerating. This is the plunge distance moved after the crossover axis has
returned to its start point coordinate.
This parameter is “program modal,” meaning that it needs to be
programmed only once in a part program. Any subsequent surface
grinding blocks (G82 -- G86) use a previously programmed value if a new
value is not programmed.
Important: In grinding fixed cycle blocks where changes are made from
absolute to incremental or incremental to absolute modes within the block,
the integrands I, J and K are always in the last mode programmed in the
block, regardless of their position in the block.
Q - plunge pick amount at crossover.
The value entered here is an incremental value used to indicate the distance
that the plunge axis moves as soon as the reciprocating axis begins
decelerating. This is the plunge distance moved after the crossover axis
reaches the crossover position defined by Z. If no value is entered for this,
then the J value is used
This parameter is not “program modal.” Any subsequent surface grinding
blocks (G82 -- G86) use the J value if a Q value is not programmed.
L - number of spark-out passes.
The number entered here (any integer from 0 to 999) indicates how many
spark-out passes are made after the final plunge depth has been reached.
Spark-out refers to repeating a final grinding pass without changing plunge
depth until there are no “sparks” (no material being removed) from the part
surface. It is a complete repetition of the final grinding pass, whether it
was only reciprocating motions (G82) or reciprocating and crossover
motions. If the last spark out pass leaves the crossover axis at its start
coordinates instead of the end point of the crossover move, then one
additional spark-out pass is made.
This parameter is not “program modal.” If a value for the number of
spark-out passes is not programmed, then no spark-out passes are executed
for that cycle.