Preventing Specification Drift
Lock specs so order five matches order one.
1. Why it matters
Specification drift is the slow, often invisible divergence between what you approved and what keeps arriving. The first order matches the golden sample; by the fifth, the LED chip has been substituted, the driver is a cheaper grade, and the aluminium is thinner — each change small, the cumulative effect a product that no longer performs or certifies as sold. Preventing drift is cheaper than discovering it in a field failure.
2. Where drift enters
Drift is usually not fraud — it is a factory optimising cost between your orders, often without malice or notice. The high-value, hard-to-see components are where it hides.
- LED chip: a brand-name reel swapped for a cheaper bin — changes lumens, CRI, lifetime.
- Driver: an efficiency or protection grade dropped — changes efficacy and failure rate.
- Heat sink: thinner aluminium or less mass — raises junction temperature, cuts lifetime.
- Optics / diffuser: a cheaper PC or PMMA — changes beam, glare and yellowing.
3. Controls that make drift visible
You cannot inspect for what you never fixed. Establish an approved baseline and check every batch against it. The golden sample and a signed, revision-controlled spec sheet are your reference; incoming inspection is where you catch the divergence.
| Control | What it locks |
|---|---|
| Golden / reference sample (both hold one, sealed) | The physical standard for disputes |
| Revision-controlled spec sheet + BOM | Named brands/models of key components |
| Engineering Change Notice (ECN) clause | No substitution without written approval |
| Incoming inspection vs sample | Actual batch conformance |
4. Make substitution require your signature
The single most effective clause is a written Engineering Change Notice requirement: the supplier may not change any component named in the BOM without your prior written approval, and a violation is a warranty and payment event, not a discussion. Pair it with a spot re-test at a lab (LED chip verification, driver teardown) on a random batch each year — the possibility of being checked is most of the deterrent.
5. Checklist
- Seal a golden sample; both sides hold one
- Name exact component brands/models in a revision-controlled BOM
- Add an ECN clause: no substitution without written approval
- Inspect every batch against the approved sample
- Lab-verify a random batch (chip/driver) annually