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Check Probe Input Status

Go to CURRENT COMMANDS > DIAGNOSTICS and verify Input #38 (or #39 for wireless) changes state when probe tip is manually touched to grounded surface.

Use a metal tool to bridge probe tip to spindle housing for reliable test contact

Inspect Probe Connections

Check probe cable connections at both the probe and the machine interface. Look for loose M8 connectors, damaged cables, or corrosion at connection points.

Power down spindle before disconnecting probe cables to avoid damage

Verify Probe Parameter Settings

Check Parameter 31 (PROBE INPUT) is set correctly - typically 38 for wired probes or 39 for wireless systems like Renishaw radio probes.

Parameter 31 must match the actual input being used or probe signals will be ignored

Test Probe Continuity

Use multimeter to verify continuity through probe cable and stylus assembly. Resistance should be less than 10 ohms from tip to signal pin.

Remove probe from spindle before electrical testing to prevent accidental machine movement

Verify G31 Move Distance

Review the G31 program line to ensure the target position allows sufficient travel distance for probe to reach the workpiece surface.

Use G31 with incremental moves (G91) and conservative distances to avoid over-travel

Check Workpiece Setup

Verify workpiece is properly fixtured and positioned where the program expects it. Confirm work coordinate system (G54-G59) is correctly set.

Incorrect work offsets can cause probe to miss workpiece entirely

Validate Probe Length Offset

Check Tool Length Offset for probe tool number in OFFSET SETTING > TOOL. Incorrect length offset causes probe to start from wrong Z position.

Use G43 H[tool#] before G31 moves to ensure proper tool length compensation

Test Manual Probe Contact

Manually jog probe to expected contact point and verify Input #38/#39 triggers when contact is made with workpiece surface.

Use slow jog speeds and watch diagnostics screen during manual contact testing

Inspect Probe Stylus Assembly

Check stylus for damage, wear, or loose connections. Verify stylus seats properly in probe body and makes good electrical contact.

Ruby ball stylus tips should be smooth and spherical - any chips or flat spots indicate replacement needed

Test Probe Trigger Force

Manually deflect probe stylus in all directions to verify smooth movement and positive return to center. Trigger force should be consistent.

Excessive force during testing can damage precision probe mechanisms

Check Probe LED Indicators

Observe probe LED status during contact testing. LED should illuminate when probe is triggered and extinguish when released.

No LED response during contact indicates internal probe electronics failure

Verify Probe Power Supply

Check probe power supply voltage at machine interface - typically 24VDC for most Haas probe systems. Measure with probe connected.

Low supply voltage can cause intermittent probe operation and false alarm conditions

Review G31 Feedrate

Verify G31 feedrate is appropriate for probe type - typically F10-F50 for touch probes. Too fast can cause probe damage, too slow may cause timeout.

Use F20-F30 for most Renishaw and Haas probes as starting point

Check Program Logic Flow

Verify G31 is preceded by proper tool call (T[probe tool#] M6) and tool length compensation (G43 H[probe tool#]) commands.

Missing tool length compensation will cause probe to start from incorrect position

Validate Coordinate System

Ensure correct work coordinate system (G54-G59) is active before G31 move and coordinates reference proper workpiece location.

Use G53 (machine coordinates) for consistent probe reference positions

Test with Single Block

Run G31 move in Single Block mode (SINGLE BLOCK key) to observe machine behavior and probe response step by step.

Keep hand on FEED HOLD during single block testing for immediate stop capability

Test Input Circuit with Jumper

Disconnect probe and jumper Input #38 pins at machine connector to simulate probe trigger. Check if input changes state in diagnostics.

Only qualified technicians should perform electrical jumper tests on machine inputs

Check Input Circuit Fuses

Locate and inspect input circuit fuses in electrical cabinet. Replace any blown fuses with identical amperage rating.

Input circuit fuses are typically 1-2 amp fast-blow types in main electrical panel

Verify Input Module Operation

Test other inputs on same input module to determine if entire module has failed or only probe input circuit is affected.

Input module replacement requires qualified electrical technician and proper lockout procedures