BOM revisions and change records

When a part changes, the old list shouldn't just vanish. Good software keeps a record of what the list used to say and why it changed.

That matters the day a customer asks about a unit you built last spring. You want to know which parts went into it then. Not which parts go in now.

The change order

The classic paper trail is the engineering change order, or ECO. Some shops call it a change notice. It's used to implement changes to components or end products.¹ Its job is to control and coordinate changes to product designs that evolve over time.¹

You don't need a big engineering department to use the idea. Even a tiny shop swaps parts now and then, and sooner or later someone asks why.

Wikipedia says a change can come from a change in material or manufacturing method.¹ That covers a part running short. It covers a switch of supplier too, and a fix made to make up for a design mistake.¹

What a change record should say

An ECO must contain at least certain information.¹ From the article's list, these are the parts that carry over to a small shop:

• What is changing, including the part number and name of the component.¹
• The reason for the change.¹
• A description of the change, often with before and after drawings.¹
• A list of documents and departments affected.¹
• Approval, by people who are authorized to approve it.¹
• When to start: immediately, during the next production run, or at some other milestone.¹

The "when to start" line is the one people skip. Say whether you'll use up old stock first or switch at once. Otherwise the shop floor guesses, and guesses differ from person to person.

How software handles it

Tools differ. Your own tool's help pages are the guide, and the ERPNext manual shows just one approach to the problem, which may not match what you're using.

In that manual, once a BOM is submitted, it can't be edited. You cancel the existing one, duplicate it and submit another.² The manual notes that a submitted BOM is linked to multiple places in the Manufacturing module, so changes can be time-consuming and tedious. That is why it advises thinking carefully before submitting.²

Unchecking "Is Active" disables a BOM so another can be used.² A default flag decides which list work orders pick up.²

Put together, an older list can stay on file without being picked for new work. That's the idea behind a revision. Short, and it works.

A simple routine for a small shop

1. Write down what's changing and why.
2. Check which other lists use that part.
3. Get a sign-off from whoever owns the product.
4. Make the new list, and switch the old one off.
5. Tell whoever buys parts and whoever builds.

Checking which other lists use the part is the step to ask your software about. Look in its help pages for a report that shows where a part is used. Parts link upward through the levels, and the page on assemblies and sub-assemblies shows how.

Part numbers belong in every change record. Naming rules for them are in the notes on item records.