1.3 Change control & configuration management: ECR/ECO/deviation control

Quality engineering is fundamentally about verifying that exactly what was intended to be built is being built. Without robust change control, maintaining the integrity of the “Golden Sample” becomes incredibly difficult, and production quality can easily drift over time. A Quality Engineer acts as a thoughtful gatekeeper of the product’s validation status. Whenever a change is made to the product or process, a portion of the original qualification is effectively reset. The goal of this system is to precisely identify that gap and ensure it is closed before mass production is allowed to resume.

Configuration management: the basis of inspection

A moving target simply cannot be inspected. Configuration Management (CM) is how the approved product baseline is established and locked down. This specific baseline then serves as the definitive, single source of truth for both Incoming Quality Control (IQC) and Final Quality Control (FQC).

Baseline integrity

Drawings & Specs: The physical drawings on the floor must always match the exact revision that is currently active in the PLM or ERP system.
Approved Vendor List (AVL): It must be noted that a resistor sourced from a new vendor is considered an entirely new part, even if the basic resistance value is identical. Different sub-tier materials can introduce unexpected reliability characteristics over the life of the product.

Revision logic

Whenever a change impacts the inspection standard—such as altering physical dimensions or updating cosmetic criteria—the revision number must be incremented, and the corresponding Quality Plan should be updated to reflect the new reality.
If a sub-component changes, such as a shift in the glue formula, it is important to re-validate the reliability compliance, even if the top-level drawing appears completely unchanged.

ECR & ECO: the re-validation trigger

An Engineering Change Order (ECO) is the formal mechanism used to trigger a re-evaluation of the DFMEA (Design Failure Mode and Effect Analysis) and PFMEA (Process Failure Mode and Effect Analysis).

The quality assessment filter

When an Engineering Change Request (ECR) is reviewed, attention must be focused primarily on the validation delta rather than just the commercial benefits or cost savings.

When there is a material change, like switching from Plastic Resin A to Resin B, new testing must be required for flammability, chemical resistance, and dimensional stability.
When there is a process change, like moving from manual screw insertion to an auto-feed system, a torque consistency capability study (Cₚₖ) and a careful visual inspection to check for new scratch risks must be required.
When there is a tolerance change, such as loosening a gap from ±0.1mm to ±0.2mm, the new stack-up analysis must always be verified to ensure that the final assembly fit is not compromised.

Pro-Tip: When a critical component changes, the ECO must not be casually approved in the system. A formal First Article Inspection (FAI) and a localized reliability test—like a 5-piece drop test—specifically tailored to validate the new configuration must be required.

Disposition of material

A good ECO always explicitly outlines the fate of any existing inventory to prevent quality issues stemming from mixed stock on the floor.

Scrap: If parts must be scrapped, physical destruction is required. For high-value items, generating a clear Certificate of Destruction is required.
Rework: Any rework instructions must be thoughtfully validated by Quality Engineering before they are attempted on the line. The post-rework yield must always be tracked to verify the method worked.
Use-As-Is: This disposition should only be permissible if the non-conformance has absolutely zero impact on product safety, long-term reliability, or the end customer’s experience.

Deviation control: managing risk exposure

A Deviation (often called a Concession) is a formal, documented agreement to accept a known non-conformance for a specific time period or limited quantity. It must be remembered that a deviation is not a structural fix; it is simply a temporary risk acceptance record.

Deviation rules of engagement

If a proposed deviation affects a Safety Critical Characteristic (SCC), it should be rejected. Safety requirements are foundational and cannot be waived.
If the deviation is purely cosmetic, physical Boundary Samples (often called Limit Samples) signed by the Quality Manager must be established. These samples provide clear, visual guidance for the inspectors on the line.
When a deviation is approved, 100% screening must be implemented or tighter AQL sampling levels adopted (such as Level III) for the duration of that deviation to protect the customer.

Traceability rules

Units produced under an active deviation must be fully traceable. The specific Batch ID or the exact Serial Number range must always be recorded. Should field failures occur later, this data allows isolation of exactly which units were built under the temporary concession.

Final Checkout: Change control & configuration management (ECR/ECO/Deviation control)

Control Point	Quality Action
Validation Delta	The Engineering Change Order (ECO) should define the specific tests needed to re-qualify the change (e.g., Thermal, Drop, EMC).
Document Alignment	It must be ensured that Incoming Quality Control (IQC) and Final Quality Control (FQC) inspection instructions are updated concurrently with the ECO release.
Stock Purge	Physical segregation of old vs. new revision parts must be verified to ensure there is 0% mixed stock.
Deviation Containment	Approved deviations should generally include increased sampling frequency or 100% screening.
AVL Control	Alternate component sources should undergo the same qualification rigor as the Approved Vendor List (AVL) primary source.
Rework Validation	Rework instructions must never be released without a verified method statement and a clear retest plan.