345

Check current Z-axis position on POSITION screen (POS key). Compare absolute machine coordinate against parameter 7071 (Z-axis tool change position) accessible via SYSTEM > PARAM > search for parameter number 7071.

Verify parameter 7073 (Tool change position tolerance) is not set too narrow. Typical value is 0.5-2.0mm. If set to 0, some systems require exact position match which may cause nuisance alarms.

Check ladder logic for ATC sequence (PMC > LADDER or use FAPT Ladder if available). Verify signal X-axis in position (typically G27.4) and Z-axis in position (G27.6) are both active before M06 execution. Use SYSTEM > PMC > PMCDGN to monitor these signals in real-time.

Review part program for proper tool change positioning. Ensure G28 Z0 (or G30) is commanded before M06, or that Z-axis moves to parameter-defined position. If using canned cycle, verify G80 cancellation before tool change.

Always establish machine zero reference (G28) before testing tool change sequences to ensure accurate position checking.

Check DIAGNOSIS screen (SYSTEM > DIAGNOSIS > search diagnostic number 300) for Z-axis reference point completion flag. Bit should show '1' if reference point return is complete. If '0', execute G28 Z0 in MDI mode.

Do not attempt tool change operations without completing reference point return. This may cause crashes or incorrect positioning.

Verify absolute position encoder battery status at SYSTEM > MAINTENANCE > Battery screen or check diagnostic 308 for battery voltage. Replace battery (typical BR-2/3AGCT4A for absolute encoders) if voltage below 3.0V.

Check parameter 1815 bit 0 (APZ: Absolute Position Detector). If set to 1, verify encoder cables are secure and check for alarm history (ALARM > HISTORY) showing position errors like SV0401 or SV0410 on Z-axis.

Monitor Z-axis position deviation in SYSTEM > DIAGNOSIS > diagnostic 300 series (typically 300+axis number). Excessive deviation (>0.5mm) during positioning may indicate servo tuning issues preventing accurate positioning for ATC.

Access PMC diagnostics at SYSTEM > PMC > PMCDGN and monitor input signals X addresses (typically X20-X40 range for ATC switches). Verify Z-axis tool change position switch signal activates when Z is at correct position. Compare against machine electrical schematic.

Check ladder program for ATC interlock logic. Search for function F345 or SUB96 (common ATC subroutines). Verify the Z-axis position OK signal paths correctly to the tool change enable coil (typically Y-output for ATC motor/solenoid).

Only qualified personnel should modify PMC ladder logic. Always backup ladder before any changes using SYSTEM > PMC > FILE > PUNCH operation.

If hard-wired position switches exist (proximity sensors, limit switches), manually inspect switch mounting and actuation at the tool change position. Use voltmeter to verify 24VDC signal present when Z-axis is at correct location.