version: "1.0.1" description: > Gear fault diagnosis workflow using vibration analysis via the predictive-maintenance-mcp server. Use this skill when the user says "gear fault", "gear diagnosis", "gear mesh", "gearbox analysis", "gear vibration", "tooth damage", "gear defect", "diagnose gear", "gear mesh frequency", "sideband analysis", or wants to detect gear faults from vibration signals.

Gear Fault Diagnosis

Detect gear faults through spectral analysis of vibration signals, focusing on gear mesh frequency (GMF) harmonics, sidebands, and modulation patterns. This workflow supports expert judgment — it never replaces it.

Prerequisite: The predictive-maintenance-mcp MCP server must be connected.

Background

Gear faults produce characteristic vibration patterns:

• Gear Mesh Frequency (GMF) = number_of_teeth x shaft_RPM / 60
• Healthy gears show GMF and low-level harmonics
• Faulty gears show increased GMF harmonics, sidebands spaced at the shaft

frequency, and broadband noise

Workflow

Step 1 — Signal Selection and Parameters

Load the signal with load_signal(filepath="gearbox_run1.csv", signal_unit="g") or pick a loaded one from list_signals(scope="memory"). Verify sampling rate and metadata with get_signal_info(signal_id="<id>"). For raw binary files (.bin/.raw/.dat), also declare sample_format and sampling_rate (or provide a companion <stem>_metadata.json) — see the signal-management skill.

Gather from the user (do NOT guess):

• Shaft RPM (or shaft frequency in Hz)
• Number of teeth on the gear of interest
• Gear ratio (if analyzing a gear pair)

Calculate:

• GMF = teeth x RPM / 60
• Shaft frequency = RPM / 60

Step 2 — Statistical Screening

Call analyze_statistics(signal_id="<id>").

Gear fault indicators (screening only, never diagnostic alone):

• Kurtosis > 3: impulsive content (possible tooth damage)
• Crest Factor > 5: localized damage
• RMS increase: overall vibration energy rise

Step 3 — FFT Analysis

Call analyze_fft(signal_id="<id>").

Inspect the spectrum for:

Systematic check of the expected GMF against the envelope spectrum:

Call check_bearing_faults(signal_id="<id>", rpm=1500, frequencies={"GMF": 800.0})

(The frequencies route accepts any labeled frequency — it is the out-of-catalog / gearbox path.)

Step 4 — Envelope Analysis (for Modulation)

Call analyze_envelope(signal_id="<id>", filter_low=500, filter_high=5000).

Center the demodulation band around GMF or its harmonics (keep it below Nyquist) to extract amplitude modulation. Sidebands in the envelope spectrum at shaft-frequency spacing corroborate gear fault modulation.

Step 5 — Advanced Spectral Analysis

Call compute_spectrogram_stft(signal_id="<id>") to check for time-varying patterns — localized tooth damage shows periodic energy bursts at the shaft rotation rate.

Call compute_power_spectral_density(signal_id="<id>") for a smoothed spectral view that highlights persistent gear-mesh patterns.

Step 6 — ISO Severity Context

Call assess_severity(signal_id="<id>", machine_group=2, support_type="rigid").

Report the zone (A/B/C/D) and urgency. The verdict requires a DECLARED signal unit — if refused, confirm the unit with the user and re-load with load_signal(filepath="<file>", signal_unit="mm/s", overwrite=True).

Step 7 — Diagnosis Summary

Classification rule (choose exactly one, cite the evidence):

• Gear tooth fault — strong evidence: GMF harmonics present AND at least

one clear sideband pair spaced at the shaft frequency AND a supporting statistic (Kurtosis > 3 or CF > 4)

• Possible localized tooth damage: partial sidebands or ambiguous

spacing — list the missing evidence needed for confirmation

• Uniform wear / increased load: elevated GMF amplitude WITHOUT sidebands

and normal impulsiveness

Each conclusion MUST cite: tools used, specific peaks (frequency and magnitude), sideband spacing vs the expected shaft frequency, and supporting statistics.

Step 8 — Report Generation

Call generate_fft_report(signal_id="<id>", max_freq=5000, num_peaks=15, rpm=1500) and optionally generate_diagnostic_report_docx(signal_id="<id>", sections={"summary": "..."}).

Important Notes

• GMF calculation requires an accurate tooth count and RPM — ask, never assume
• Multi-stage gearboxes: analyze each stage separately
• Gear and bearing faults can coexist; if bearing frequencies also appear,

recommend the bearing-diagnosis skill as well

• Use cautious language for all diagnoses; the final call rests with a

qualified engineer

• All processing is local — no data leaves the machine