Engineering Change Order

An Engineering Change Order (ECO) is the formal mechanism for making controlled changes to a product's design, Bill of Materials, specifications, or manufacturing process after the design has been baselined. An ECO documents: what is changing, why it is changing, what the impact is (on cost, schedule, form, fit, and function), what testing is required to validate the change, and who has approved it. The ECO process ensures that changes are evaluated, documented, and communicated to all affected parties before implementation.

ECOs exist because uncontrolled changes are dangerous. A well-intentioned component substitution that saves $0.50 per unit can introduce an EMC failure, a mechanical interference, or a software incompatibility that costs orders of magnitude more to diagnose and fix. The ECO process creates a mandatory review checkpoint: the change cannot be implemented until the ECO is reviewed by the affected stakeholders (engineering, manufacturing, quality, supply chain) and approved by a change control board.

ECO classification systems distinguish between types of changes. 'Class 1' or 'immediate' changes are safety-critical and must be incorporated into all in-process and in-field units. 'Class 2' or 'rolling' changes are incorporated at the next production run. 'Class 3' changes are deferred to the next product revision. Classification determines urgency, retrofit scope, and customer notification requirements.