Engineering change order: what an ECO must say, and how to run one with an outside factory

A production mix-up can start as a small change nobody wrote down. Here is what the document has to say, and what changes when the factory is not yours.

Filed under Line watch and quality control

Short answer: An engineering change order (ECO) is the approved document that says exactly what is changing on a product, why, who signed off and when the change takes effect. With an outside factory it does one more job: it is the written record that the supplier may build to the new revision, and it settles what happens to the parts already made.

An engineering change order sounds like paperwork for large companies, but small brands need it most once production sits at a factory they do not run. A verbal "just move that hole" can reach the toolmaker and miss the inspector, and you find out when a carton arrives built to two different drawings. This note covers how an ECO differs from an ECR and an ECN, what one must say, and how to run one with a contract manufacturer. Our note on what contract manufacturing is covers the wider relationship.

ECR, ECO and ECN: three jobs, easily mixed up

One published definition says an ECO "describes and authorizes the implementation of an engineering change to the product and its approved configuration documentation". Software vendors and quality teams usually split the change into three steps:

• Engineering change request (ECR). Someone proposes a change and explains why it is needed.
• Engineering change order (ECO). The approved change and its exact scope.
• Engineering change notice (ECN). The message telling everyone who must act on it.

Accruent's guide puts the order in the middle: "The ECO is the authorization step: it comes after a change has been requested and reviewed, and before the change is communicated and put into effect." The names are not universal. Wikipedia lists the ECO as "also called an engineering change notice", and Accruent adds: "Some organizations combine the order and the notice into one document, and some industries name or sequence the three differently." So when a factory sends you an "ECN", read what it does rather than what it is called. If it asks you to approve something, treat it as an order. If it says a change has already been made, you have a different problem, covered below.

What an ECO must say

The contents are simple and the discipline is in leaving nothing out. Greenlight Guru, writing for medical device makers, says "it should list everything that may be affected by the change, including materials, assemblies, documents, and processes". A workable ECO covers:

1. What is changing. Part number, part name and the drawings involved, with the old and new revision letters.
2. Why. A design error, a cost reduction, a material that is no longer available, a customer request.
3. Before and after. A marked-up drawing or a photo showing only the detail affected.
4. What else it touches. Mating parts, the bill of materials, packaging, labels, test fixtures, work instructions.
5. Cost and time. Tooling work, new samples, lead time, and any change to the unit price.
6. When it takes effect. A date, a lot number or a purchase order, and what happens to existing stock.
7. Who approved it. Named people on both sides, with the date.

Do not leave item 6 blank. Wikipedia's article says the instruction should state when to introduce the change: "immediately (scrapping current inventory), during the next production run, or at some other milestone".

Changes you did not ask for

The hardest ECOs to manage are the ones nobody writes. Wikipedia lists among the causes of change "A change in material or manufacturing method. This can be caused by a lack of material availability, a change in vendor, or to compensate for a design error." The first two often start on the factory's side. A resin grade goes on allocation, a component reaches end of life, a sub-supplier is replaced to save money, and each can seem too small to mention. Bild's guide describes the reverse direction, when you want something altered upstream: "A supplier ECO is used to request revisions to components or materials supplied by external vendors."

Close the gap in the purchase terms. Write that no change to material, process, sub-supplier, tooling or production location happens without written approval, and that the approved sample remains the standard until you sign a new one. Our note on why lot three drifted from the golden sample shows what that drift looks like, and our note on injection molding materials covers what to lock down on the resin line.

Running an ECO with an outside factory

Most ECO advice assumes everyone works for one company, with a change control board in the same building. Arena notes that the order can go to "external design teams or supply chain partners", and with a contract manufacturer that is your main audience. A few habits help:

• One owner on each side. Your factory contact and your own engineer or project lead, named in the ECO. Changes passed through sales staff or chat threads tend to lose detail.
• Ask for the impact before you approve. "A good ECO contains the full description, analysis, cost, and impact of a change", in Arena's words. Have the factory quote the tool work, the samples and the schedule in writing, and read that quote as you would an NRE charge.
• Say who owns the result. If steel is recut or a new insert is made, the changed tool should follow the same terms as the original. See our note on tooling custody. For boards, our note on who owns what in EMS covers the files.
• Translate it if your factory works in another language. Have the drawing callouts and the instruction confirmed back to you in writing, so you know both sides read them the same way.

Cutting in the change: stock, lots and proof

SimplerQMS says an ECO also sets out "how to handle work-in-progress (WIP), field inventory, and supplier stock". In a factory relationship, that line is about money.

Before you sign, settle these:

• Parts already made. Use as is, rework or scrap, and who pays. The contract may already say, so check it first.
• Raw material and components on order. A factory may have bought ahead for your forecast, and it will expect to raise that with you.
• Mixed cartons. Mark the new revision on the carton and the lot record so old and new parts cannot be mixed without anyone noticing.
• Proof. Decide what shows the change worked. Dimensional changes usually call for a new first article inspection on the affected features, and a new approved sample. Add the new revision to your pre-shipment inspection checklist, or the inspector will check against the old drawing.

Some programs carry formal rules on top of this. Arena notes: "In industries with regulatory requirements, like the medical device industry, having a full history of every change to a product is mandatory." Automotive buyers have their own approval process, covered in our note on automotive injection molding.

A small brand's version

You do not need software to start. A numbered one-page form, a shared folder holding only current revisions and an emailed approval will do for a handful of parts. Keep old revisions in a clearly marked archive, not in the same folder. Then send the change to everyone who works from that drawing, because the failure is usually in the distribution. Wikipedia says "The most important part of making a change is to see that all pertinent groups are notified and all documents updated." Accruent's warning is that "a change that is approved but never distributed leaves teams working from superseded information", and it concludes: "Most rework traces back to an uncontrolled or out-of-date document rather than to the change itself."

Keep changes few, too. A design for manufacturability review before steel is cut catches the changes that are cheapest to make, because after that point most of them involve tool work.

Where Jack fits

JCH works as a US point of contact for manufacturing built at partner factories, so changes are part of the job: getting the revision to the people on the floor and checking it was followed. JCH itself holds no certification. Where a buyer requires ISO, UL or ISTA, Jack matches the program to partner facilities and accredited labs that hold them. You can see what we take on at our capabilities page.

If a change is coming on a product you already make, send Jack the current drawing, what needs to change and how much stock is on hand or on order. He will tell you what the ECO should cover before the factory quotes it.

Straight answers

What is the difference between an ECR, an ECO and an ECN?

An engineering change request proposes a change and gives the reason. An engineering change order is the approved change and its exact scope. An engineering change notice tells everyone who must act on it. Some companies merge these or use the names differently, so check what each document actually does.

What should an engineering change order include?

The part number and drawings affected, the reason, the old and new revisions with a before-and-after view, everything else the change touches, the cost and time involved, when it takes effect, what happens to existing stock, and who approved it.

Does a small brand need a formal ECO process?

It needs the record, not the software. A numbered one-page form, one folder of current revisions and a written approval from each side are enough for a handful of parts. What matters is that nothing changes at the factory without that approval.

Who pays for an engineering change at an outside factory?

It depends on your contract and on who asked for the change. Ask the factory to quote the tool work, samples, schedule and any stock affected in writing before you approve it, and settle who covers parts already made in the ECO itself.

Do I need a new first article after an engineering change?

If the change affects dimensions, fit, material or the process, you will usually want a new first article on the affected features and a newly approved sample. Otherwise later lots have nothing current to be compared with.

How this note was made: researched and drafted with AI assistance, checked against the sources listed below and edited at JCH Design & Manufacturing.