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:
|LS1||Tool pocket up position feedback||Limit switch|
|LS2||Tool pocket down position feedback||Limit switch|
|LS3||Tool magazine counter and brake sensor ON||Proximity switch|
|LS4||Tool magazine positioning feedback||Proximity switch|
|LS5||Tool magazine origin feedback||Proximity switch|
|LS10||CAM box brake feedback||Proximity switch|
|LS11||Tool clipping positioning feedback||Proximity switch|
|LS12||CAM box origin feedback||Proximity 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:
|Function||Brake FB||Tool clip position||CAM box origin|
|CAM Box Origin||1||0||1|
|CAM rotation 90′||0||0||0|
|CAM box point of clipping||1||1||1|
|CAM down by 115mm||0||0||0|
|CAM rotation 180′||0||0||0|
|CAM up by 115mm||0||0||0|
|CAM box point clipping||1||1||0|
|CAM rotation 90′||0||0||0|
|CAM box origin||1||0||1|
I/O signals used for ATC ladder program:
|ADDRESS||OUTPUTS COMMANADS TO ATC||DEVICE|
|Y2.6||Tool magazine rotation in reverse||Relay 24VDC|
|Y2.5||Tool magazine rotation in forward||Relay 24VDC|
|Y3.7||Tool magazine motor ON||SSR|
|Y3.1||CAM box motor ON||Relay 24VDC|
|Y5.0||Tool magazine motor brake ON||Relay 24VDC|
|Y5.4||CAM box motor brake release||Relay 24VDC|
|Y5.3||Tool clamp / de clamp output||Solenoid 24VDC|
|X5.7||Tool pocket up position feedback (LS1)||Limit switch|
|X6.0||Tool pocket down position feedback (LS2)||Limit switch|
|X6.1||Tool magazine counter and brake sensor ON (LS3)||Proximity switch|
|X6.3||Tool magazine positioning feedback (LS4)||Proximity switch|
|X6.4||Tool magazine origin feedback (LS5)||Proximity switch|
|X6.5||CAM box brake feedback (LS10)||Proximity switch|
|X6.6||Tool clipping positioning feedback 9LS11)||Proximity switch|
|X6.7||CAM box origin feedback (LS12)||Proximity switch|
|X0.6||Tool clamp push button||Pressure switch|
|X0.7||Tool unclamp push button||Pressure switch|
|X21.4||ATC clockwise PB||Push button switch|
|X21.5||ATC counter clock wise PB||Push button switch|