Engineering Changes: The Drawing Is New, but the Shop Floor Makes the Old Part

Engineering approves revision B on Tuesday. The purchasing team orders the new component. On Wednesday, the shop floor finishes 300 units using revision A.

Each department followed the information it had. The change lacked an agreed boundary between old and new production.

An engineering change needs an effective date or another explicit applicability rule, a list of affected orders and a decision about stock already made. Updating the drawing is only one part of that work.

A revision needs an applicability rule

Suppose, in a hypothetical example, a pump housing changes from a four-hole pattern to a six-hole pattern. The revised housing needs a new gasket and a different drilling operation.

“Use revision B from Tuesday” leaves questions open. Does it apply to orders released on Tuesday, operations started that day or products dispatched afterwards? Existing customer commitments may also require a specific revision.

An engineering change notice (ECN) should make the rule clear. A date, serial-number range or identified set of orders can define applicability. The right boundary depends on product and customer requirements.

500 ordered, 300 started, 200 untouched

Assume an order contains 500 housings. Of these, 300 have already passed drilling under revision A; 200 have not started. Revision B adds five minutes of drilling per unit.

Applying the change to the untouched 200 adds 200 × 5 = 1,000 minutes, or 16 hours 40 minutes of drilling.

The remaining 300 need a separate technical decision. If rework is approved and takes eight minutes each, it adds 2,400 minutes, or 40 hours. If rework is impossible, replacement production changes material demand and delivery timing.

These times are illustrative, not recommendations for a real housing. They show why a revision must reach capacity planning before a new delivery promise.

Keep the affected records together

For each change, check:

• Drawing and specification revision.
• BOM components, quantities and approved alternatives.
• Routing operations, tools, inspection and processing times.
• Open purchasing and production orders.
• Finished goods and work in progress.
• Customer approval or contractual revision requirements.

The product's identity and revision must stay traceable. The existing article on item master data explains why uncontrolled variants quickly become an operational problem.

Give operators one clear instruction

A message saying “new drawing attached” is easy to miss. The instruction should identify the affected order, applicable revision, old material disposition and the point where production must pause for clarification.

Record acknowledgement where the process requires it. Do not silently replace the document behind an operation already in progress. Preserve the record of what was actually built.

Bring one change to the demonstration

In a factory.online demonstration, use a real example of a revision change. Ask the team to show how the affected product data, production orders and schedule are handled, including work already started. Verify the exact revision-control workflow your business needs.

Book a demo with an old drawing, its approved replacement and one open order. Those three records reveal far more than a generic feature list.