905-2772

Check current Z position

Press POS key and verify actual Z position against machine coordinate system. Note if position is beyond expected travel range.

Use REF key to display reference point status - unreferenced axes can cause false position readings

Verify software travel limits

Access MOD function, select machine parameters, check MP1010 (Z- limit) and MP1020 (Z+ limit) values match machine specifications.

Only modify travel limits if you have machine documentation - incorrect values can cause crashes

Perform controlled retraction

Use Manual mode with reduced feedrate override (10-25%) to move Z-axis away from limit position using handwheel or direction keys.

If axis won't move, try EMERGENCY STOP reset followed by reference point return

Re-establish reference point

Execute reference point return for Z-axis using REF key, then verify position accuracy with known reference tool or workpiece.

Ensure clear path before reference point return to prevent collisions

Check encoder diagnostics

Access DIAG menu, select axis diagnostics, review Z-axis encoder signals for signal quality, amplitude, and error counters.

Look for intermittent signal drops or amplitude variations that indicate cable or encoder issues

Inspect encoder cables

Visually inspect Z-axis encoder cable routing for damage, tight bends, or interference with moving parts. Check connector security at both encoder and TNC ends.

Power down system before disconnecting encoder cables to prevent damage

Verify encoder mounting

Check encoder mechanical coupling and mounting for looseness, contamination, or damage that could affect signal generation.

Slight encoder movement during axis motion indicates loose coupling

Test with encoder substitution

If available, temporarily connect known good encoder or use TNC encoder simulation mode to isolate encoder hardware from control issues.

Document original encoder parameters before substitution

Inspect Z-axis travel path

Visually examine entire Z-axis travel for chips, coolant buildup, damaged way covers, or foreign objects blocking movement.

Lock out power and use proper lockout/tagout procedures before manual inspection

Check way lubrication

Verify way lubrication system operation and oil levels. Check for proper distribution to Z-axis ways and ballscrew.

Dry ways often cause binding that manifests as position errors under load

Test manual movement

With servo drives disabled, attempt manual Z-axis movement to identify binding points or excessive resistance.

Support heavy Z-axis components during manual movement testing

Examine ballscrew and nut

Inspect Z-axis ballscrew for damage, contamination, or excessive backlash. Check ballnut mounting and preload adjustment.

Metallic debris on ballscrew indicates wear - collect sample for analysis

Check servo drive status

Access servo diagnostics through DIAG menu, review Z-axis drive status, fault history, and current monitoring values.

Note any recurring fault patterns or abnormal current readings during movement

Verify servo parameters

Compare current servo tuning parameters (KV, acceleration, following error limits) with machine documentation or backup values.

Incorrect servo parameters can cause instability or damage - document changes

Test servo response

Use TNC servo optimization functions to test Z-axis response characteristics and identify tuning issues.

Perform tests at reduced speeds initially to prevent damage from unstable tuning

Check power supply voltages

Measure servo drive DC bus voltage and motor supply voltages under load conditions to identify power supply issues.

Use proper PPE and follow electrical safety procedures when measuring high voltages

Review active program

Examine current NC program for Z-axis moves, coordinate system calls (G54-G59), and tool length compensation values that may exceed travel.

Use program simulation mode to trace Z-axis path without actual movement

Verify coordinate system setup

Check work coordinate system offsets in coordinate system table, ensure values are reasonable for current workpiece setup.

Large coordinate system offsets can cause unexpected axis movements

Validate tool length compensation

Review tool table entries for excessive or incorrect tool length values that could cause Z-axis positioning errors.

Cross-reference tool lengths with physical tool measurements

Reset coordinate systems

Clear work coordinate system offsets and re-establish using proper setup procedures with known reference points.

Document existing coordinate systems before clearing in case restoration is needed