4-20 CHAPITRE 4: ELECTRICS
ALPHA ST320 S2
4.3. Signals from the lathe to the bar feed system
The interface logic can be configured with service parameters. Only trained personnel should
change these settings.
a) 24V DC power supply
All the signals from the lathe are powered by the 24V DC from the bar feed system. When the
corresponding relay is energized at the lathe, the 24V DC travels through the corresponding contact and
returns to the PLC. The PLC hence receives lathe signals.
b) Emergency stop signals from the lathe
This contacts XT8 and XT9 are part of the emergency stop loop of the bar feed system. When the
emergency circuit is open between XT8 and XT9, the bar feed system goes to EMERGENCY STOP
MODE and arise an e01 alarm and energize relay R1.
c) Lathe chuck signal / Lathe clamp signal (PLC input X11)
Chuck signal is for confirming the status of lathe chuck (collet, clamping device). This signal starts feeding
and bar change process of bar feed system by itself as well as combination with other signals.
The signal logic will be handled according to MODE 2 setup.
d) Lathe in automatic mode (PLC input X12)
This signal indicates that the lathe is in automatic mode. The lathe is executing the machining program
cyclically.
The signal logic will be handled according to MODE 3 setup.
e) BACK START / Load command (PLC input X13)
Generally the bar change process will be automatically started with chuck signal when the BAR END
signal is ON. Exceptions:
- The part requires multiple feeds.
- The lathe is equipped with a sub-spindle
- The lathe is of twin spindle type
To prevent collisions between the part being transferred to the second spindle and the newly loaded bar
stock when there is a simultaneous loading. The lathe must control the loading process of a new bar. This
signal will be used as a BACK START / LOAD COMMAND from the lathe. Refer to MODE 7 and 19 for
related set up.
The signal logic will be handled according to MODE 4 setup.
f) TORQUE STOP (PLC input X14)
When the bar feed system is in automatic mode. The pusher pushes forward all the time except it’s
currently returning for bar loading. Under certain circumstances, this behaviour might damage either tool
or sub-spindle when the chuck is open without stopper in front. Whenever this signal is present, the
pusher stops its movement immediately as long as the torque stop signal is ON.
Generally this signal will be ON before chuck open when the end of bar is reached. (The signal logic will
be handled according to MODE 5 setup.) After the last part is machined, the stopper is usually not
present anymore. The bar feed system must not push the bar when the chuck is open. To avoid this, the
TORQUE STOP signal must be ON.
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