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 a robust system to manage changes, maintaining the integrity of the approved product baseline—often called the “Golden Sample”—becomes very difficult. Over time, production quality can easily drift from this standard. A Quality Engineer acts as a thoughtful gatekeeper of the product’s validation status. Think of it this way: whenever a change is made to the product or its manufacturing process, a portion of the original qualification is effectively reset. The goal of a change control system is to precisely identify that gap in validation and ensure it is properly closed before mass production is allowed to resume.

Configuration management: the basis of inspection

You cannot effectively inspect a moving target. Configuration Management (CM) is the practice of establishing and locking down the approved product baseline. This specific, documented baseline then serves as the definitive, single source of truth for all inspection activities, from Incoming Quality Control (IQC) to Final Quality Control (FQC).

Baseline integrity

Drawings & Specifications: The physical drawings used on the production floor must always match the exact revision that is currently active in the Product Lifecycle Management (PLM) or Enterprise Resource Planning (ERP) system. Any mismatch here is a direct source of error.
Approved Vendor List (AVL): It’s important to understand that a component sourced from a new vendor is considered an entirely new part, even if its basic specification (like a resistance value) appears identical. Different sub-tier materials and manufacturing processes can introduce unexpected reliability characteristics over the product’s lifetime.

Revision logic

Whenever a change impacts the inspection standard—such as altering physical dimensions or updating cosmetic criteria—the drawing revision number must be incremented. The corresponding Quality Plan must also be updated to reflect this new reality.
If a sub-component changes internally, such as a shift in an adhesive formula, the assembly must be re-validated for reliability compliance. This is necessary even if the top-level assembly drawing appears completely unchanged.

ECR & ECO: the re-validation trigger

An Engineering Change Order (ECO) is the formal mechanism used to authorize a change and, critically, to trigger the necessary re-evaluation of the product’s design and process risks (DFMEA and PFMEA).

The quality assessment filter

When reviewing an Engineering Change Request (ECR), the Quality Engineer’s primary focus should be on the validation delta—what new testing or analysis is required—rather than just the commercial benefits or cost savings.

Material Change: For example, switching from Plastic Resin A to Resin B necessitates new testing for properties like flammability, chemical resistance, and dimensional stability.
Process Change: Moving from manual screw insertion to an auto-feed system requires a capability study (Cₚₖ) on torque consistency and a careful visual inspection plan to check for new risks, such as part scratching.
Tolerance Change: Loosening a dimensional tolerance, such as from ±0.1mm to ±0.2mm, requires the new tolerance stack-up analysis to be verified. This ensures the final assembly fit and function are not compromised.

Disposition of material

A well-written ECO always explicitly outlines the fate of any existing inventory (the “old” parts) to prevent quality issues from mixed stock on the production floor.

Scrap: If parts must be scrapped, they should be physically destroyed. For high-value items, a clear Certificate of Destruction should be generated.
Rework: Any rework instructions must be validated by Quality Engineering before they are released to the production line. The post-rework yield must then be tracked to verify the method is effective.
Use-As-Is: This disposition should only be permitted if the non-conformance has 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 a limited quantity of product. It is crucial to remember that a deviation is not a permanent fix; it is a temporary record of accepted risk.

Deviation rules of engagement

If a proposed deviation affects a Safety Critical Characteristic (SCC), it should be rejected. Safety requirements are foundational and non-negotiable.
If the deviation is purely cosmetic, establish physical Boundary Samples (often called Limit Samples) that are signed off by the Quality Manager. These samples provide clear, visual guidance for inspectors on what is acceptable.
When a deviation is approved, implement 100% screening or adopt tighter AQL sampling levels (such as Level III) for its duration. This added scrutiny helps protect the customer.

Traceability rules

Every unit produced under an active deviation must be fully traceable. The specific Batch ID or the exact Serial Number range must be recorded. If field failures occur later, this data allows you to isolate exactly which units were built under the temporary concession.

Recap: Change Control & Configuration Management

Change Object	Core Requirement / Trigger	Mandatory Action / Validation	Pass/Fail Criteria	Document / Traceability
Baseline Integrity	Drawings & specs on floor match active PLM/ERP revision. AVL part from new vendor = new part.	Lock baseline in PLM/ERP. Control via IQC/FQC.	FAIL: Any mismatch between floor and system.	Approved Configuration Record.
Material / Process Change	Change impacts reliability, safety, or inspection standard.	Execute new tests (e.g., flammability, Cₚₖ). Perform targeted reliability test (e.g., 5-piece drop).	PASS: New validation closes identified risk gap.	ECO, updated DFMEA/PFMEA, test reports.
Tolerance Change	Alters dimensional or functional stack-up.	Perform and verify new tolerance stack-up analysis.	PASS: Final assembly fit/function not compromised.	ECO, revised drawing.
Deviation / Stock Disposition	Temporary acceptance of known non-conformance.	For SCC: REJECT. For cosmetic: Establish signed Boundary Samples. Implement 100% screening or AQL Level III.	PASS: Zero safety impact; full traceability achieved.	Deviation Authorization, Batch/Serial Number log.
ECO Execution	Change authorizes production and triggers re-validation.	Define and execute validation delta. Specify inventory disposition (Scrap/Rework/Use-As-Is).	PASS: All validation complete; old inventory controlled per plan.	ECO with explicit disposition instructions.