Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 853)

Allen-Bradley 7300 Series CNC
Tape Compatibility
Appendix D
D-3
G28 and G29 Automatic Thread Cutting or Roughing Cycle
G28 and G29 are not standard 7300s Lathe G-codes, but have been
provided to enable automatic thread cutting or roughing. Both G28 and
G29 are used for the Automatic Thread Cutting cycle. This Automatic
Thread Cutting feature simplifies part programming of multiple-pass
thread cutting operations for straight or tapered constant-lead threads.
With this feature, an entire multi-pass thread cutting operation is
programmed in only two data blocks. These blocks contain parameters
that specify the following characteristics of the thread:
final thread depth
thread depth of first pass
infeed path
infeed feedrate
thread length
thread lead
pullout-in-lead distance
return pass clearance
return pass feedrate
Important: G28 and G29 are programmed consecutively within the part
program. The first automatic threading block must contain a G28 code; the
next block must contain a G29 code. An error occurs if you program these
G-codes separately.
When a G33 code is programmed in a G29 data block, it establishes
Thread Cutting mode for the automatic multi-pass thread cutting cycle.
When a G01 is programmed with a G29 data block, the G01 establishes the
Linear Interpolation mode for automatic multi-pass roughing cycles.
Either a G33 or a G01 has to be accompanied by a G29 data block in order
to perform any of the cycles mentioned above.
Important: The G01 code programmed in the G29 block is not modal; the
control automatically cancels the linear interpolation mode after a
multi-pass roughing cycle is completed.