Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 417)

Axis Motion
Chapter 14
14-41
Moving to the Hard Stop
The G24 code must be in a block that programs a position for one and only
one axis. The G24 code is non-modal (G--code group 0).
The active cutting mode when the G24 code is executed must be G01
(linear interpolation). Other cutting modes and rapid traverse (modal
group 01), are invalid during a G24 block.
Once the G24 code is executed the axis moves towards the programmed
endpoint at the currently active feedrate. When the axis enters the
detection zone set up with the integrand word, the control expects to
encounter a hard stop. If a hard stop is detected before entering this
detection zone, the control generates an error. An error is also generated if
the control reaches the programmed endpoint without encountering a hard
stop. Both of these error conditions force a cycle stop.
Detecting the Hard Stop
A hard stop is detected when the control’s torque output reaches a Hard
Stop Detection Torque that the system installer configured in AMP. This
torque limit must be reached after entering the detection zone and before
reaching the G24 blocks’programmed endpoint or an error is generated.
Once an axis is positioned against a hard stop, that axis remains in the hard
stop state until it is programmed away from the hard stop. While against
the hard stop, the control applies a set holding torque to the servo keeping
the axis firmly pinned against the hard stop. This hard stop holding torque
amount is determined by the system installer in AMP.
Only one axis can be positioned against a hard stop at any one time.
Attempting to position more than one axis against a hard stop results in a
programming error. Once an axis is positioned against a hard stop, it must
be programmed away from the hard stop before another axis can use the
hard stop feature. You can program an axis that is currently in the hard
stop state to a different hard stop location with a G24 block provided the
hard stop is in a direction opposite the current hard stop holding torque.