351

Check the part program around the alarm occurrence. Look for synchronous control commands (G51.1 for tandem axis enable, G50.1 for tandem disable, or custom M-codes) and verify a G04 dwell or M00 stop precedes the command to ensure complete axis settling.

Navigate to SYSTEM > DIAGNOSIS and check diagnostic number 300 (servo position deviation) for the axes involved in synchronous control. Non-zero values indicate the axis has not reached the commanded position and is still settling.

Review parameters 8131-8134 (tandem control axis numbers) and 8135-8138 (tandem control slave axis numbers) to identify which axes are configured for synchronous operation. Verify these axes show zero velocity on the CURRENT POSITION screen before synchronous commands are issued.

If using PMC control for synchronous enable/disable, examine the PMC ladder (PMCLAD screen) for the synchronous control request signal timing. Add interlock logic requiring in-position signal (G signal G0007 bit for each axis) and velocity zero confirmation before toggling synchronous control activation.

Ensure PMC ladder changes are backed up and tested in single-block mode before production use.

Check parameter 1826 (in-position check width) for the axes involved in synchronous control. Values set too large (typically >100) may allow synchronous commands while axes are still within acceptable positioning tolerance but not fully stopped. Reduce to 10-50 encoder pulses as appropriate.

Verify parameter 1825 bit 0 (in-position check enable) is set to 1 for precise position detection. Navigate to SYSTEM > PARAM and search for parameter 1825 to confirm the setting.

Monitor DIAGNOSIS screen numbers 300-307 (position deviation for each axis) in real-time during the move sequence preceding the synchronous command. If deviation does not reach zero within expected time, tune servo gains (parameters 1825, 1827, 1828) or increase dwell time in program.

Servo tuning changes can affect machine performance and should be documented and tested incrementally.

Add a G04 P500 (500ms dwell) or longer immediately before the synchronous control enable/disable command in the part program to guarantee complete axis stop and settling time.

Access PMC ladder program (SYSTEM > PMC > PMCLAD) and locate the rung controlling synchronous control request output (typically F or Y address mapped to control input). Verify interlocks include axis in-position signals (G0007.0-G0007.7 for axes 1-8) and feed hold inactive (G0004.5).

Document all PMC addresses and logic before making changes. Incorrect PMC modifications can cause unexpected machine behavior.

Check for TMR (timer) instructions in the PMC ladder that delay synchronous control activation. Add or increase timer value (e.g., TMR T100 500 for 500ms delay) after move complete signal to ensure axis settling before synchronous control state change.

Review the CNC to PMC interface signals on SYSTEM > PMC > DGN > G (CNC to PMC signals). Confirm G0007 in-position bits for relevant axes are ON (1) before the synchronous control request signal transitions. Use trace function to capture signal timing if intermittent.