An SHW UF5 equipped with a TNC 155 displayed the message Z-axis measuring system defective during morning startup, and the hydraulics did not start. The reported root cause was contamination. Treat the Z-axis feedback path as the primary fault area; do not assume that the hydraulic system itself has failed.
Observed startup fault
The fault appeared when the machine was switched on. Two conditions occurred together: the Z-axis measuring-system error was active, and hydraulic startup did not complete. The available evidence does not identify the contaminated component or establish whether the control intentionally inhibited the hydraulics, so diagnose the measuring system before drawing conclusions about the hydraulic circuit.
Supported causes to inspect
| Condition | Evidence status | Required check |
|---|---|---|
| Contamination in the Z-axis measurement path | Confirmed cause in the reported case | Locate and remove contamination without disturbing alignment or wiring. |
| Failed illumination source in a glass scale | Conditional hypothesis | Check only if the machine uses a glass-scale system with this component. |
| Broken cable | Conditional hypothesis | Inspect the Z-axis measuring-system cable for damage or loss of continuity. |
| Intermittent connection | Conditional hypothesis | Inspect relevant connections for looseness or intermittent contact. |
Diagnostic and recovery procedure
- Inspect the accessible Z-axis measuring-system components for contamination. Because contamination was the confirmed cause, address it before replacing parts.
- If glass scales are installed, inspect the scale-related illumination source, cable, and connections. Keep these as hypotheses until testing identifies a failure.
- Restart the machine and confirm that the Z-axis measuring-system message no longer appears.
- Verify that hydraulic startup now completes. If the message remains, continue testing the Z-axis feedback path rather than treating the listed hypotheses as confirmed defects.
Verification criteria
Recovery requires both observed symptoms to clear: the TNC 155 must start without the Z-axis measuring-system fault, and the SHW UF5 hydraulics must start. If cleaning restores both functions, the result supports contamination as the cause. If only one condition clears, the evidence is insufficient to identify the remaining fault.
FAQ
What causes a TNC 155 Z-axis measuring system defective message?
Contamination was the confirmed cause in this SHW UF5 case. If glass scales are installed, also test the illumination source, cable, and connections as possible causes.
Can the Z-axis measuring-system fault prevent hydraulic startup?
The error and failure of the hydraulics to start occurred together in the reported case. The evidence does not establish the control sequence, so clear and verify the Z-axis feedback fault before diagnosing the hydraulic circuit separately.
How do I verify the SHW UF5 fault is cleared?
Restart the machine and confirm that the TNC 155 no longer displays the Z-axis measuring-system message and that the hydraulics start successfully.
