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Check DIAGNOSIS > PARAMETER > #0300 (Reference Position Return Completion) bits for each axis to verify which axes have completed reference return. Bit pattern shows completion status per axis.

Access SYSTEM > PARAM > #1815 (reference return sequence setting). Verify bits are set correctly for your angular axis configuration. If bit for angular axis is ON, that axis MUST complete reference before orthogonal axes.

Perform manual reference return in correct order: First execute REF on the angular/rotary axis (A, B, or C axis), wait for completion, then reference orthogonal axes (X, Y, Z).

If using G28 in program, ensure angular axis movement is commanded and completed in a separate block before linear axis G28 commands. Example: N10 G28 C0; then N20 G28 X0 Y0 Z0;

Check DIAGNOSIS > SERVO > DGN #0300 to confirm angular axis (A/B/C) reference completion bit is OFF. Also check DGN #0010-#0013 for grid signal detection on the angular axis during reference approach.

Verify parameter #1815 bit setting matches your machine angular axis configuration. Clear alarm with RESET, then manually jog angular axis and retry reference return while observing grid signals on DIAGNOSIS screen.

Inspect angular axis proximity switch (dog) and reference position encoder marker (grid). Check I/O DIAGNOSIS (PMC > DGN) for decel dog signal (*DEC) and zero point signal (grid) during slow reference approach.

If grid signal intermittent, check encoder cable connections to servo amplifier and verify DIAGNOSIS > SERVO shows stable position feedback with no SER000 or SER043 encoder alarms during axis motion.

Encoder cable issues may cause position loss after reference completion

Access SYSTEM > PARAM and locate parameter #1815 (reference return sequence). Document current bit settings and compare against machine builder specifications or backup parameter list.

Changing #1815 requires parameter write enable (PWE bit 0 = 1) and power cycle

Verify machine actually has angular/rotary axes installed. If machine is 3-axis mill without rotary table, all bits in #1815 should typically be 0 (no dependency). Consult machine electrical drawings.

If #1815 settings are incorrect, enable parameter write (SYSTEM > SETTING, set PWE), modify #1815 to correct configuration, disable PWE, and power cycle the CNC completely.

Incorrect #1815 settings can prevent all reference returns or cause positional errors

After power cycle, perform complete reference return sequence in order specified by updated #1815. Monitor DIAGNOSIS #0300 bits to confirm each axis sets reference complete flag properly.