When Material Codes Are a Mess, Everything Downstream Is: How to Define Your Coding Rules

One material, two names in two warehouses

On count day the warehouse clerk brought IT two slips. The 0402, 1kΩ chip resistor had two part numbers: one created three years ago, one added two years ago when the supplier changed. The parts sat in two locations, and only the sum of the two numbers matched the quantity on hand.

Purchasing ordered against the model number in the supplier catalog. Receiving booked the number the clerk remembered. The same lot was sometimes A and sometimes B. A customer complaint that asked which parts were used could trace only half. The other half sat on the number nobody remembered.

Nobody had stated which change still meant this resistor and which change required another number. Without that rule, purchasing, the warehouse and engineering each created numbers from the paper in front of them. That is where the second number came from.

Where this resistor goes wrong next

Each number looks right on its own. Inventory matches the shelf only when the two numbers are added; either number alone still looks reconciled. Purchasing cannot compare the two suppliers' prices on one number, so a price gap is read as a supplier difference. Traceability breaks at the part number: the missing half raises no error, it simply cannot be found. The report counts one resistor as two, so days of supply, obsolete stock and purchasing concentration stay high. The dashboard does not alarm, because the figure is too big, not wrong.

The reverse is worse: one number covers two parts that cannot replace each other. Stock looks sufficient, the wrong part is issued to the line, and the error reaches finished goods and shows up at the customer.

A part number answers one question

A part number answers only whether this is the same interchangeable item. Two resistors with the same package, value and tolerance, which can be swapped on the board without changing assembly or inspection, are one number. Changing supplier is not, by itself, a reason to create a second number.

What does not belong in the part number are relationships and states that change: supplier, customer, project, year, price, quantity on hand, location, lot. Put them in the number and every change retires a number.

The front of the number can carry a major and a mid category, so a person can see raw material, semi-finished or finished, and roughly which family. The rest is a serial. The serial means nothing except that it does not repeat. Leave four or five digits. Three digits start forcing an exception or a renumber after a few hundred codes. Add a check digit only when people often copy the number by hand and also scan it. Not every plant needs one.

Drawing and revision, specification, material, finish, unit of measure, pack, whether inspection is required, substitutes and sources belong in fields. A field says what this number is now. It does not decide whether a new number is required: once the old and new parts are not interchangeable, issue a new number instead of writing the new attribute onto the old one.

When a new part number is mandatory

What you actually decide, day to day, is the next change. If the parts remain interchangeable, keep the number. If they do not, issue a new one. The table follows that test, not the mere fact that something changed.

Switching supplier for the same grade leaves the resistor the same resistor: do not create a number, add the supplier to the source list. Changing plain cold-rolled steel to galvanized changes the inspection, so a new number is required. Where automotive or medical rules require the manufacturing source to be distinguished, keep one internal part number and control it on the approved-supplier list. Do not build the supplier into the number. Record who decided, which drawing or change order they used, and the effective date. A decision nobody can explain six months later was never made.

Material and finish are recorded in fields, and they are also common reasons to issue a new number. The field describes the number as it is now. When the old and new parts can no longer replace each other, issue a new number. Do not write galvanized onto the old cold-rolled number. Many systems store only the part number on a historical document and read the current material master when the document is opened. Change the field, and the old document shows today's material. If you need the material as it was, write it on the document at posting, or keep a change record.

Block new duplicates, then retire the old numbers

Put a few hundred duplicates on the table first and nobody will decide. Leave the front door open and a third number appears after the cleanup. Close this pair of resistors in this order:

1. Put duplicate checking on the request page first. A later request for this resistor, by the same specification, must hit the existing number and must not create a new one.
2. Set the unique key by category. This resistor uses package, value and tolerance, not a machining drawing number. Machined parts more often use drawing, specification, material and finish. Do not force one key on the whole plant.
3. Engineering and quality review the candidate list. The system only points at numbers that may be duplicates. It does not decide for them.
4. Keep one number. Prefer the one already written into a BOM. If both are, or neither is, keep the one used more widely. If that still does not separate them, keep the one created earlier.
5. Deactivate the other number. Do not delete it. Record the map to the surviving number, the effective time and the operator. Point open BOMs and purchasing lists at the surviving number. Posted documents keep the number they were posted with, so the complaint lot still opens on the number used that day.
6. A deactivated number cannot be selected on a new purchase, receipt or issue.

When one number is actually two different things, reverse the order: separate the physical stock and the in-transit quantity first, and only then split BOM and document references, again with a map. If you cannot separate the physical parts, do not split the number in the system yet.

Do not mix up the four codes

A part number answers what it is: one interchangeable item, one number, issued by the master-data administrator after approval. A lot number answers which lot, created at receipt or labor reporting. A serial number answers which piece, created when the item is serialized. A location code answers where it sits, set by the warehouse.

Write the lot into the part number and every lot adds a number. Write the location into the part number and every move requires a new number. If a code changes because the place or the lot changed, it is not a part number.

Who is allowed to say this is a new material

The second number was created by whoever was busy when the supplier changed. Purchasing and the warehouse use the number. They do not decide whether it is a new material. That decision belongs to engineering or process engineering: they produce the drawing or the change order and write the conclusion and the effective date. The master-data administrator issues the number after approval, and records the time and the map when deactivating it. The system checks for duplicates at request time and, on a hit, shows the existing number. IT keeps the duplicate check and the permissions working. IT does not rule on the specification.

The plant has one request entry. A number that has not been approved cannot be referenced by a purchase order, a receipt or a BOM.

In JEDP the material master is a form, and attributes are fields. Creation and deactivation go through a workflow. A duplicate hit shows the existing number. After deactivation the old number remains on historical documents, and new receipts and issues cannot select it. The map, the deactivation time and the operator are stored on the same transaction. Configure this with forms, workflow and permissions. Do not build a separate coding program.

Back to count day

Accept against those two slips, not against the policy document.

1. Request by package, value and tolerance. The request hits the existing part number and cannot produce a second one.
2. Adding one more supplier whose parts remain interchangeable does not change the number. A change that breaks interchangeability, such as plain cold-rolled steel to galvanized, requires a new number. Do not overwrite the material field on the old number.
3. Open the receipt for the complaint lot. The part number is still the one used that day. If the material at that time must remain visible, it is on the document or in the change record, not only on today's material master.
4. Look up the deactivated number. The map, the deactivation time and the operator are visible, and new purchasing and issue cannot select it.
5. Until the request is approved, no document can reference it.
6. Groups that are not yet merged can be exported, with the actual numbers listed. This pair should appear on that list until it is closed.

Do not merge numbers at scale while three things are still open. If drawings and BOMs are still changing, a number merged today will split tomorrow. If nobody owns issuance, the next purchase order will create a third number. The number on a shipped lot is traceability evidence. Renumbering all history at once costs more than it saves. Freeze new duplicates first, then close category by category.

Once this pair is closed, the two count slips become one quantity. Purchasing compares price on the surviving number, the complaint lot still opens on the number used at the time, and the report no longer needs someone to add the two resistors back together by hand.

• Form engine: model, fields and page generation
• Process engine: one rule set for approval and business flow
• Organization engine: people-centric organization master data
• Permission engine: row- and field-level authorization
• Choosing a digital foundation: set the yardstick with these 8 questions before talking price
• Traceability cannot stop at lot ID—three gates from lot-level to station-level
• Why does the nearest pallet always ship? FIFO needs hard blocks, not wall posters
• Implementation pitfalls & cycle-definition checklist