In this guide 6 sections
A panel gets built wrong when the drawing changes after BOM release and the shop floor keeps working from the old print or list. Revision locks, change notes naming affected jobs and a stores block on superseded items stop that, and the fix is process first, software second.
How the wrong panel actually happens
The design engineer swaps a 40 amp breaker for a 63 amp one after the customer comments, and the drawing is revised, but the BOM in stores stays unchanged. Purchase has already ordered the old breaker.
The wireman holds a printed wire list from last week, mounts what stores issued, wires to the old terminals and sees the panel pass a visual check.
The mistake surfaces at testing or, worse, at site, by which time the enclosure is cut, the cables are cut and the delivery date has gone. Nobody lied. Each person worked from the paper in front of them, and that paper was out of date by one revision and nothing on the page said so.
Find where the revision stopped travelling
Trace one failed job backwards from the test failure, asking who knew about the change, when they knew and how they were told. Usually it was a phone call.
Walk the floor with a notebook and read every printed drawing, wire list and terminal schedule for a revision letter and a print date. A print with neither is a guess.
Check purchase orders raised before the revision, since those are the quiet source of unusable breakers, contactors and terminal blocks that nobody can return.
- Revision letter missing from the printed drawing
- Change told verbally, never written
- Purchase order raised before the change reached purchase
- Old wire list still pinned near the panel
- Stores issuing against the earlier BOM
Revision locks: one released BOM per job
One job, one live BOM. When engineering releases revision C, revision B is marked superseded, stores cannot issue against B, and purchase sees a warning on every open order tied to it.
The lock is a simple rule. It works only when the system applies it, because people forget under deadline pressure and a tired storekeeper at six in the evening will issue whatever the slip says.
Give each BOM line a status of reserved, issued, fabricated or fitted, so a revision tells you at once how much material is already committed to the old design.
Change notes that name jobs and parts
Every revision needs a short change note stating what changed, why, which jobs are affected and which stage each job has reached. A design stage job needs a quiet update. A wiring stage job needs a full stop.
Put the note where the supervisor will see it, not in a folder, and get a signed acknowledgement from stores, purchase and the wiring lead. Print it on coloured paper, so a supervisor skimming a pile of routine job cards cannot mistake it for ordinary paperwork.
Where parts were already bought, record on the same note whether they return to stock, move to another job or get written off, and who approved that decision.
- Old and new part, make and rating
- Jobs affected and their current stage
- Stock already issued, ordered or fabricated
- Acknowledgement from stores, purchase and wiring
A practical way to start this month
Pick your three most recent revisions. For each one, count the days that passed before stores, purchase, the wiring lead and the test bay all knew, because that number shows the size of your gap.
Then agree one rule, kept small: no printed drawing leaves the design office without a revision letter and a date, and superseded copies are collected back from the floor.
Only then move the locks into software, starting with the single product family that generates the most revisions and the most site complaints.
Drawing change note form
A one page form: header block for job number, drawing number, both revisions and date, then three columns for part out, part in and reason. At the foot sits a stage tracker for every affected job, next to signature boxes for stores, purchase and the wiring lead.
Open a blank worksheet to printQuestions owners ask
How soon after a drawing change must the BOM be reissued?
Before any further purchase or issue happens on that job, because every day of delay lets another breaker, cable or terminal block go out against the old list. Release both revisions as one event.
What if wiring has already started when the drawing changes?
Stop and assess. List the wires already run that the change touches, then decide whether to rework them or accept a deviation with the customer’s written approval. Record the decision on the change note.
Can a spreadsheet enforce revision locks?
Not reliably. A spreadsheet can show a revision column, but it cannot stop a storekeeper from issuing a superseded breaker, lug or relay, because nothing in the sheet checks release status. Enforcement needs a system that checks first.
Who owns the change note?
The design engineer writes it. The production manager confirms jobs and stage, and stores and purchase acknowledge it before any work continues, so no desk can later say the note never reached it. Keep the signed copy with the job file, since it is your evidence if the buyer later disputes the cost of rework.