How to Manage ECOs in Mass Production

Once a product reaches mass production, many teams assume that the design is effectively “locked-in.” In reality, engineering changes are common throughout the lifecycle of the product. Engineers are always trying to make improvements, reduce costs, and more. It’s important to track these changes and set up a process of how to manage ECOs in mass production. 

An Engineering Change Order (ECO) in mass production is not just needed by the engineering team but the entire production, quality, and operations team. If changes are not clearly controlled and communicated, outdated parts can make it to the production line, inventory can become obsolete, and production schedules can be disrupted. Managing ECOs in mass production requires discipline across engineering, supply chain, quality, and manufacturing to ensure changes are implemented cleanly, at the right time, and without unintended consequences.

What an ECO Really Means in a Production Environment

In mass production, an ECO is far more than a drawing revision or a CAD update. Any approved change has downstream effects that can impact the bill of materials (BOM), tooling, test procedures, packaging, certifications, and even how operators build the product on the line. Unlike development, where changes are expected and are controlled, production ECOs will affect inventory, purchase orders, and assembly processes.

This is what makes ECOs in mass production inherently higher risk. A single change can create multiple versions of the same product if it is not tightly controlled. Parts built to an old revision can coexist with updated components, suppliers may work from outdated data, and production teams may unknowingly assemble mixed configurations. To manage ECOs in mass production effectively, companies must treat each change as a coordinated operational event ensuring that all affected systems and stakeholders are aligned before the change is released.

Common Triggers for ECOs During Mass Production

ECOs during mass production are often driven by factors that come up once a product is being built at scale. Suppliers may identify manufacturability issues, components may become unavailable or increase in cost, or quality issues can influence design changes. 

Customer feedback and returns can also drive ECOs after the product is launched. Issues that were not evident during validation or pilot runs may only appear once hundreds or thousands of units are in use. While these triggers are common and often unavoidable, the key risk is not the change itself but how quickly and informally it is introduced. Without a structured process to manage ECOs in mass production, well-intentioned fixes can create confusion, inventory exposure, and inconsistent builds across production lots.

Establishing Clear ECO Ownership and Approval Flow

To manage ECOs in mass production effectively, ownership and decision-making authority must be clearly defined. Engineering may initiate the change, but production ECOs require input from quality, supply chain, and manufacturing to fully understand the impact. Without a defined approval flow, changes can be released informally, creating misalignment between teams and suppliers.

A structured ECO process ensures that every change is reviewed for cost, timing, inventory exposure, and production risk before it is approved. This includes identifying who has final sign-off authority and who is responsible for communicating the change downstream. Clear ownership prevents last-minute decisions, reduces confusion on the factory floor, and ensures that ECOs are implemented deliberately rather than reactively once mass production is underway.

Managing Revision Control and Documentation

Revision control is one of the most important mechanisms to manage ECOs in mass production. Every approved change must be tied to a clearly defined revision level that is consistently reflected across drawings, BOMs, specifications, and work instructions. If even one document remains outdated, it increases the risk that old parts or processes make their way into production.

Effective documentation control also requires defining when a new revision becomes active. This can be tied to a specific PO, lot number, or production date, but it must be unambiguous. Production teams and suppliers should never be left to interpret which version to build. Strong revision control creates a single source of truth and ensures that changes are implemented cleanly, without mixing old and new configurations on the production line.

Controlling Inventory and Work-In-Process During an ECO

When an ECO is approved in mass production, existing inventory immediately becomes a risk factor. Raw materials, components, and work-in-process may already reflect the previous revision, and without a clear plan, these parts can unintentionally flow onto the production line. Managing this transition requires visibility into what inventory exists, where it is located, and how it will be handled once the change is released.

Companies must decide whether existing parts can be consumed, reworked, segregated, or scrapped, and those decisions should be documented as part of the ECO. Successfully managing inventory during a change is a core requirement to manage ECOs in mass production, as it directly protects quality, delivery schedules, and cost.

Communicating the ECO to the Supplier and the Factory Floor

Clear communication is often the deciding factor between a smooth ECO rollout and a production disruption. Simply sending updated CAD files and the BOM is not enough when managing changes in mass production. Suppliers and factory teams must receive a formal engineering change notice that clearly identifies what has changed, the effective revision, and when the new version is to be built.

Equally important is confirmation. Suppliers should acknowledge receipt and understanding of the ECO, and production teams should have updated work instructions before the change reaches the line. Line leaders and operators need to know when the transition occurs and how to identify the correct revision. Strong communication ensures that ECOs are implemented consistently and prevents outdated parts or processes from continuing unnoticed in mass production.

Validating the Change Before Full-Scale Production

Not every ECO requires a full requalification, but changes introduced during mass production should be validated before being released broadly. Depending on the scope of the change, this may involve building updated samples, running a limited pilot run, or performing targeted testing to confirm that the change does not introduce new quality or manufacturability risks.

Validation provides confidence that the ECO will behave as expected once it reaches the production line. It also gives suppliers and production teams an opportunity to identify issues early, when adjustments are still manageable. Taking the time to validate changes is a critical step to manage ECOs in mass production, especially when the product is already shipping or committed to customer delivery timelines.

Monitoring the ECO After Release

Releasing an ECO into mass production is not the final step. Once the change is implemented, teams should actively monitor early production data to confirm that the update is performing as intended. This includes tracking yield, scrap rates, quality escapes, and any changes in cycle time or assembly difficulty.

Early monitoring allows issues to be identified while the production volume is still limited, reducing the impact if corrective action is required. Feedback from the factory floor and suppliers is especially valuable during this period, as it often reveals practical challenges that were not evident during review or validation. Ongoing oversight ensures that ECOs in mass production deliver real improvements rather than introducing new problems downstream.

Conclusion: Managing ECOs in Mass Production

Once a product is in mass production, ECOs must be managed with the same rigor as any other core production process. ECOs impact inventory, suppliers, production schedules, and product quality, and treating them as informal engineering updates creates unnecessary risk. Companies that consistently manage ECOs in mass production recognize that change control is a shared responsibility across engineering, operations, quality, and supply chain.

With the right workflow ECOs can be implemented without disrupting production or compromising quality. In many cases, a well-managed ECO process becomes a competitive advantage, allowing teams to respond quickly to issues and improvements while maintaining control as production scales.