Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 214)

Running a Program
Chapter 7
Running a Program
Chapter 7
7-32
To perform a block retrace operation:
1. Press the <CYCLE STOP> or activate the <SINGLE BLOCK>
feature button to stop program execution.
2. Press the <BLOCK RETRACE> button.
After the <BLOCK RETRACE> button is pressed the control will retrace
the block that was being executed when the cycle stop occurred or retrace
the block just completed if the single block button was pressed, provided
that the block is a legal block for retrace.
While the block retrace function is active, the light in the
<BLOCK RETRACE> button will be on. The block that was shown as
active when the block retrace was activated will still appear as the
currently active block in the program display area during the entire use of
the block retrace function.
Important: If the <CYCLE STOP> button was used to halt execution to
begin a block retrace the control re-executes the portion of the block that
has been executed. For example, if the block requests an axis move of 20
millimeters and the axis has moved 12 millimeters when the
<CYCLE STOP> button is pressed, a block retrace will reverse the axis
direction 12 millimeters.
All retraced blocks are executed at the feedrate programmed for that block
though this may be modified by the use of the <FEEDRATE OVERRIDE>
switch.
Press the <CYCLE START> button at any time during a block retrace to
return the cutting tool to normal forward execution. Program execution
will return to the normal forward direction from the currently retraced
block. The control executes the retraced blocks in normal order until the
tool is positioned at the start point of block retrace. From this point it
continues program execution in a normal fashion unless
<SINGLE BLOCK> is active. If <SINGLE BLOCK> is active the control
will halt execution when the return from block retract is complete.
While block retrace is active the control disables all jog features with the
exception of <JOG RETRACT> . MDI is not available to insert blocks
during a block retrace operation.