Methodology — Extending Warranty to 2, 3 and 4 Years

Executive rationale for the years 2–4 cost computation, ready for board presentation.

1. Objective

Estimate, per model, the additional cost the company would absorb by extending the factory warranty from 12 to 24 months, and propose a commercial premium that covers this risk with a defined margin.

2. Data sources
  • Claims (last 5 years): 26.684 approved warranty claims, with failure date (CTL_FAILURE_DATE) and delivery date (CTL_DELIVERY_DATE).
  • Fleet (last 10 years): 13.798 delivered machines — used to measure the exposed fleet in each window.
  • Model: grouped by the prefix before the '-' (e.g., D51EX-22 → D51EX, PC200-8M0 → PC200).
3. Core assumption — time-based window

A failure is allocated to Year 1 if it occurs within 12 months of delivery; to Year 2 if it occurs between 12 and 24 months. Only machines that have actually completed the window enter the denominator (≥12m for Y1, ≥24m for Y2). This avoids overstating cost using new fleet that has not yet had the chance to fail (censoring treatment).

4. Formulas
Frequency Yn (claims/machine) = Claims Yn / Fleet exposed ≥n×12m
Avg cost per claim Yn = Total cost Yn / Claims Yn
Cost / machine Yn = Frequency Yn × Avg cost per claim Yn
Weibull bathtub model — projection of years 3 and 4
Weibull reliability: R(t) = exp[−(t/η)^β] · cumulative hazard H(t) = (t/η)^β · hazard h(t) = (β/η)(t/η)^(β−1)
β < 1 → infant mortality (decreasing hazard) · β = 1 → constant · β > 1 → wear-out (increasing hazard)
r21 = (Cost / machine Y2) / (Cost / machine Y1) → β = log2(1 + r21)
Weibull bathtub: H(t) = (t/η)^β → increment of year k ∝ k^β − (k−1)^β
Cost / machine Y3 = Y2 × (3^β−2^β)/(2^β−1) · Y4 = Y3 × (4^β−3^β)/(3^β−2^β)
Δ Cost (extension 12 → 48m) = Y2 + Y3 + Y4
Suggested premium = Δ Cost × (1 + margin%)

Important: Frequency is not failure probability — it is the average number of claims per machine in the window. Values above 100% (e.g., 230%) mean that, on average, each machine generated more than one claim in the period (different components, multiple interventions). This is normal in heavy-equipment warranty and is the correct metric to project cost (Frequency × Avg ticket).

Year 1 is already covered today, so the extension cost starts at Year 2. Years 3 and 4 are not observed yet: they are projected from the Weibull bathtub shape β fitted on the measured Y2/Y1 ratio, keeping the same claims base and 12-month windows.

5. Numeric example — WA200
Fleet exposed ≥12 months2.059
Fleet exposed ≥24 months1.747
Claims Y1 / Y24.719 / 957
Frequency Y1 / Y2 (claims/machine)2.29 / 0.55
Avg cost per claim Y1 / Y2$2,735 / $4,474
Cost / machine Y1$6,269
Cost / machine Y2 (observed)$2,451
r21 → β (Weibull bathtub)39.1% → 0.476
Cost / machine Y3 (projected)$1,856
Cost / machine Y4 (projected)$1,552
Δ Cost (extension 12 → 48m)$5,859
Suggested premium (20% margin)$7,031
6. Decision read
  • Rate Y2 < Y1 in most models: failures concentrate in the early months (infant mortality). Good signal to extend warranty.
  • Avg cost Y2 ≥ Y1: when a failure occurs in Year 2, it usually involves larger components — that's why Δ is not proportional to the rate.
  • Models with high Δ and high Rate Y2 require a higher premium or exclusion from the standard offer; models with low Δ are natural candidates for the extension.
7. Limitations and mitigations
  • Time-based window (not operated hours). Models with highly variable usage profiles may have under/overestimated rates.
  • 5-year claims history — recently launched models have smaller samples; the minimum-fleet filter mitigates this noise.
  • Does not include parts/labor cost inflation; annual review is recommended.
  • The premium margin (dashboard slider) absorbs variability, admin expenses, and profit — it does not replace formal actuarial analysis for large contracts.