Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 727)

Program Interrupts and
Dressing Interrupts
Chapter 22
22-7
When the return from interrupt is executed (M99 in the interrupt program),
the control generates a linear move to the end-point of the last-remembered
move for retrace. The moves are then retraced, returning the wheel back to
the start-point of the interrupt. This may not be the same location in the
calling program if a different wheel offset has been activated.
Immediate vs. Delayed Interrupts
Your system installer determines in AMP if an interrupt occurs
immediately upon request, or if it is delayed until the end of the currently
executing program block. When immediate is selected as the interrupt
type, the control decelerates the axes to a stop when the interrupt request is
made and promptly executes the interrupt program. When delayed is
selected, the control decelerates the axis at the end of the currently
executing block. Once in position at the end of this block, the control
executes the interrupt program.
During reciprocation, including reciprocation caused by execution of a
grinding cycle:
immediate interrupts are executed immediately regardless of the current
status of the grinding operation
All axis motions are decelerated to a stop, including reciprocation
motion, and the interrupt program is executed.
delay interrupts are executed at the end of the currently executing motion
The current reciprocation move, and any motions normally generated by
the cycle at this reversal point (any pick, plunge, or dither motions), are
decelerated to their endpoints. The endpoint of reciprocation is defined
as either the primary or secondary reversal points. Once at the endpoint
with axis motion stopped, the interrupt program is executed.
When the interrupt program is completed, control is returned to the calling
program and program execution (and reciprocation) resumes.
Important: If you execute an interrupt during reciprocation, including
reciprocation caused by execution of a grinding cycle, you should use the
dressing interrupts. Both immediate and delay type program interrupts can
cause major finish problems on the workpiece if reciprocation is decelerated
across the part. See page 22-10 for details on dressing interrupts.