236-A301

Verify Switch Signal in Diagnostic Mode

Navigate to MOD -> Test Functions -> Axis/Spindle Signals. Select the affected axis and observe the reference mark signal (REF) while manually moving the axis over the reference switch position. Signal should clearly change state.

Ensure machine is in safe position before manual movement. Use handwheel at reduced feedrate.

Check PLC Input Assignment

Access MOD -> Machine Parameters and verify MP6xxx series (PLC inputs). Confirm the correct PLC input is assigned to the axis reference switch. Cross-reference with electrical diagrams.

Common assignments: MP6410.x for linear axes reference inputs. Verify input number matches actual terminal connection.

Inspect Reference Switch Hardware

Physically inspect the reference switch/cam for mechanical damage, correct positioning, and secure mounting. Check switch cable continuity and proper connection at both switch and PLC input terminal.

Inductive switches require proper target distance (typically 2-4mm). Proximity switches can fail due to magnetic debris accumulation.

Test Switch at PLC Terminals

Using a multimeter, measure voltage/signal at the PLC input terminal while actuating the reference switch. Should show clear ON/OFF states (typically 24VDC). Compare to adjacent known-good inputs.

Use appropriate measurement tools. Do not short terminals or measure with power off on active switching circuits.

Verify Encoder Reference Pulse Detection

Go to MOD -> Test Functions -> Position and select the affected axis. Observe the 'Reference marks' counter while moving the axis. Counter should increment at regular intervals matching the encoder's distance-coded reference marks.

Linear encoders typically have reference marks every 50mm or 100mm. Rotary encoders usually have one reference mark per revolution.

Check Encoder Signal Quality

In MOD -> Test Functions -> Encoder Test, monitor signal amplitude and error counters for the affected axis encoder. Signal quality should be within specification (typically >1.0Vpp, errors should be zero).

Excessive position errors or signal degradation indicate encoder cable damage, contamination, or failing encoder electronics.

Verify MP1035 Reference Mark Search Window

Check machine parameter MP1035.x for the affected axis. This defines the maximum distance to search for encoder reference mark after switch detection. Increase value if necessary (typical: 50-200mm for linear axes).

If MP1035 is too small, the control may pass the encoder reference mark before completing the search algorithm.

Inspect Encoder Installation and Cables

Check encoder mounting security, scale/tape cleanliness, and proper cable routing. Verify shielding continuity and separation from power cables. Look for oil, chips, or magnetic contamination on exposed linear scales.

EnDat encoders show specific error messages in encoder test. Distance-coded marks can be damaged by scratches on linear scale tape.

Review MP1010 Homing Direction

Access MOD -> Machine Parameters -> MP1010.x for the affected axis. Verify direction matches machine builder specification (0 = positive direction, 1 = negative). Incorrect direction causes axis to move away from reference.

Direction must move axis toward the reference switch and into the reference mark search zone.

Verify MP1020 Homing Sequence Type

Check MP1020.x to confirm correct homing sequence type. Common values: 1 = via negative limit and reference switch, 2 = via positive limit and reference switch, 3 = reference switch only. Must match machine configuration.

Incorrect sequence type can cause axis to search in wrong direction or skip required limit switch contact.

Check MP1030/MP1031 Traverse Distances

Verify MP1030.x (distance to reverse off limit switch) and MP1031.x (distance to reference switch). Values must allow sufficient travel to clear switches and find reference mark. Compare to actual measured distances.

MP1030 typical value: 10-50mm. MP1031 should be greater than actual distance from limit to reference switch plus safety margin.