330-0080

Access Machine Parameters

Press MOD key, select 'Machine Parameters' from the TNC menu, navigate to MP7500.x where x is the affected axis number.

Always backup machine parameters before making changes using the data backup function.

Verify Travel Range Settings

Check MP7500.0 (negative limit) and MP7500.1 (positive limit) values against machine drawings and physical limit switch positions.

Ensure values are within physical machine limits to prevent crashes.

Test Axis Movement

Use Manual mode (MAN) to slowly jog the axis and verify it stops at software limits before reaching hardware limit switches.

Use reduced feed rate override (10-25%) when testing limit positions.

Reset Alarm and Re-reference

Clear alarm with CE key, perform reference point return using REF mode for the affected axis.

Ensure axis is clear of limit switch before attempting reference return.

Check PLC Status

Access PLC program via MOD key, select 'PLC' menu, monitor limit switch input status (typically M7xxx series markers) while manually actuating switch.

Use the PLC status display to see real-time input states without multimeter.

Inspect Physical Switch

Visually inspect limit switch for mechanical damage, proper mounting, and correct actuation distance. Check for debris or coolant contamination.

Lock out machine power and follow LOTO procedures before physical inspection.

Test Switch Continuity

With machine power off, use multimeter to test switch contacts and cable continuity from switch to TNC input module.

Check cable flex areas and entry points where wiring commonly fails.

Verify Input Module

Check TNC digital input module LED indicators and swap input channels if possible to isolate hardware vs. wiring issues.

Only qualified personnel should work on TNC input/output modules.

Check Reference Status

In Manual mode, verify the REF indicator shows green for all axes. Red REF indicator means reference point is lost.

Reference status is also visible in the position display area of all operating modes.

Perform Reference Return

Select REF mode, choose affected axis, press NC Start to execute reference point return sequence.

Ensure axis can move freely and is not against limit switch before referencing.

Verify Encoder Function

Check encoder signals in the diagnostic menu (MOD > Diagnosis > Encoder) for proper signal quality and absence of error messages.

Look for consistent signal amplitude and proper phase relationship between encoder channels.

Check Reference Mark

Verify encoder reference mark (R-track) is functioning by monitoring diagnostic display during slow axis movement through reference position.

Encoder or reference mark failure requires immediate attention to prevent position errors.

Visual Inspection

Examine the axis travel path for obvious obstructions, crashed tooling, workpiece interference, or mechanical damage.

Do not attempt to move axis until obstruction is cleared and damage assessed.

Check for Mechanical Binding

With drives disabled, manually check if axis can move freely by hand (where possible) or look for signs of mechanical binding.

Listen for unusual noises when attempting manual movement - grinding or binding sounds indicate mechanical issues.

Inspect Drive Components

Check ballscrews, linear guides, and coupling components for damage, excessive wear, or foreign material contamination.

Damaged mechanical components can cause unpredictable axis behavior and must be repaired before operation.

Clear Obstruction and Test

Remove any obstructions, clear alarm with CE key, and test axis movement at reduced feed rates in Manual mode.

Always use feed rate override at 10-25% when testing after clearing mechanical issues.

Review Active Program

Check the NC program line that was executing when alarm occurred, verify coordinates are within machine travel range.

Use the program graphics simulation to visualize tool path before running on machine.

Check Preset Table

Access preset table (PRESET TABLE softkey in Manual mode) and verify work coordinate system values are correct for current setup.

Incorrect preset values can shift entire program outside safe machine envelope.

Verify Tool Length Compensation

Check tool table entries for excessive or incorrect tool length values that may cause Z-axis limit violations.

Tool length errors are common cause of Z-axis limit switch trips during tool changes.

Simulate Program Path

Use TNC program simulation mode to verify complete tool path stays within machine limits before running program.

Always simulate new programs or setups before running in automatic mode.