Fanuc PLC ladder program for Automatic Tool Changer (ATC)


ATC stands for Automatic Tool Changer and it is used in CNC machines like VMC, HMC, and special purpose machines.

ATC is used to change the tools in machines and increase the productivity of the machine. ATC is controlled by Electrical motor and PLC programs.

Parts of ATC:

ATC consists of following parts:

  • Tool magazine.
  • Tool pockets.
  • Cam box or Arm drive unit.
  • Tool changer arm.

Electrical parts for ATC:

  • Tool magazine motor (Used to rotate tool magazine).
  • CAM box motor (Used to change tool or rotate the tool changer arm).
  • Limit switches (Get feedback from the limit switch and send it to PLC).
  • Proximity switches (Get feedback from proximity switch and send it to PLC).

Limit switches and Proximity switches of ATC:

LS1Tool pocket up position feedbackLimit switch
LS2Tool pocket down position feedbackLimit switch
LS3Tool magazine counter and brake sensor ONProximity switch
LS4Tool magazine positioning feedbackProximity switch
LS5Tool magazine origin feedbackProximity switch
LS10CAM box brake feedbackProximity switch
LS11Tool clipping positioning feedbackProximity switch
LS12CAM box origin feedbackProximity switch



Initially tool pocket is in a horizontal position, now possible to rotate tool magazine, to reach required tool position


Now the tool magazine is rotating till the required tool position is reached. After the required tool reached, the sensors LS3 (Tool magazine counter and brake sensor ON) and LS4 (tool magazine positioning feedback) become ON. Due to this tool magazine, the motor gets OFF.


After completion of sequence-2, the spindle head will come to the tool changing point and completes the spindle orientation.


Command M-code ‘M6’ for tool changing operation, presently tool pocket is in up position, it is now waiting for tool pocket down command from PLC, once tool pocket is down and LS2 (Tool pocket down) is ON, after confirmation of LS2=1, the next steps of tool changing function will start.


Now you have to switch ON CAM box motor, to rotate the tool changing arm to the tool clipping point. Make sure that LS11 (Tool clipping position feedback) and LS12 (CAM box origin feedback) should be OFF when you switching ON the CAM box motor


Now make tool clamp, (tool clamp solenoid ON). Start the CAM box motor. Now CAM box pulls down tool changing arm by115mm down and rotates 180° and rise up again 115mm up.


Now tool changing arm reached its original position and now LS10 and LS11 becomes 1

Electrical safety interlocks for ATC:

  • In ATC, the movements of tool magazine motor and CAM box motor should be very fast, so that to avoid wrong operations in tool change. For this we must write PLC program required to switch ON relays, solenoids, sensors. I/Os in LEVEL-1 of PLC.
  • Before going to start tool change command, we have to take confirmation feedback of previous tool position reached.
  • Don’t change tool, when tool magazine is rotating.
  • Don’t rotate tool magazine or tool magazine motor, if tool pocket is in down position.
  • Don’t change the tool, if spindle is not in tool changing position.
  • Don’t change the tool, if spindle orientation isn’t completed.
  • Don’t move the spindle head, if arm hasn’t in it’s home position.
  • Use overload relay in power circuit of tool magazine motor and CAM box motor, to protect motors from over current in circuits.

ATC Feedback signal status:

FunctionBrake FBTool clip positionCAM box origin
CAM Box Origin101
CAM rotation 90′000
CAM box point of clipping111
CAM down by 115mm000
CAM rotation 180′000
CAM up by 115mm000
CAM box point clipping110
CAM rotation 90′000
CAM box origin101

I/O signals used for ATC ladder program:

Y2.6Tool magazine rotation in reverseRelay 24VDC
Y2.5Tool magazine rotation in forwardRelay 24VDC
Y3.7Tool magazine motor ONSSR
Y3.1CAM box motor ONRelay 24VDC
Y5.0Tool magazine motor brake ONRelay 24VDC
Y5.4CAM box motor brake releaseRelay 24VDC
Y5.3Tool clamp / de clamp outputSolenoid 24VDC
X5.7Tool pocket up position feedback (LS1)Limit switch
X6.0Tool pocket down position feedback (LS2)Limit switch
X6.1Tool magazine counter and brake sensor ON (LS3)Proximity switch
X6.3Tool magazine positioning feedback (LS4)Proximity switch
X6.4Tool magazine origin feedback (LS5)Proximity switch
X6.5CAM box brake feedback (LS10)Proximity switch
X6.6Tool clipping positioning feedback 9LS11)Proximity switch
X6.7CAM box origin feedback (LS12)Proximity switch
X0.6Tool clamp push buttonPressure switch
X0.7Tool unclamp push buttonPressure switch
X21.4ATC clockwise PBPush button switch
X21.5ATC counter clock wise PBPush button switch

Leave a comment