Okuma Alarm A-8647 – Hand Open/Close Switch NG

Alarm A-8647 indicates that the manual open/close operation was commanded, but the corresponding confirmation signal was not received within the specified time set in the machine parameters.

In simple terms, the control issued a hand open or hand close command (for example, chuck, door, tailstock, or other actuator), but the expected feedback signal did not return.

This alarm occurs when:

• A manual open/close command is executed

• The output signal is sent correctly

• The status input (confirmation signal) does not match

• The response time exceeds the parameter-defined limit

Possible causes include:

• Faulty open/close limit switch

• Defective proximity sensor

• Broken wiring or loose connector

• PLC input/output mismatch

• Incorrect parameter timing setting

• Mechanical obstruction preventing full movement

When this alarm appears, the machine blocks further operation to prevent unsafe movement or mechanical damage.

Recommended actions:

1. Check the mechanical movement of the device (is it actually opening/closing?).

2. Inspect limit switches and proximity sensors.

3. Verify PLC I/O signals in the diagnostic screen.

4. Check wiring and connectors.

5. Confirm parameter time settings for open/close monitoring.

This is typically an interlock or feedback problem, not a CNC software issue.