Lot Traceability in Manufacturing: A Practical Guide

Forward and backward traceability

Backward traceability answers: what went into this product? Starting from a finished lot or serial number, you trace back to the components, raw material lots and suppliers. Forward traceability answers: where did this go? Starting from a suspect material lot, you trace forward through every lot that consumed it, to the shipments and customers that received it. A recall needs both, usually in that order: identify the cause backward, then find exposure forward.

The data model behind traceability

• Lot: a quantity of material or product made or received under the same conditions, with a unique identifier.
• Lot link (genealogy): a record saying lot B consumed lot A, ideally with quantity.
• Supplier lot: the supplier's own lot number recorded at receiving, plus the certificate of analysis or conformity.
• Shipment: which lots went to which customer and when.
• Quality records: inspections, NCRs and holds attached to the lot.

Choosing lot size

Lot size is a trade-off. A smaller lot means a smaller recall scope but more records. A practical rule is to break a lot whenever something that could affect quality changes: a new raw material lot, a shift change, a tool change or a machine restart after maintenance. If you cannot break the lot, record the change as an event on the lot so it is still visible in an investigation.

Worked example (illustrative)

A supplier tells you that resin lot R-118 may contain contamination. Backward check: R-118 was received on two dates and consumed in moulding lots M-501 and M-502. Forward trace: M-501 was assembled into finished lots F-77 and F-78; M-502 went into F-79. F-77 and F-78 are shipped to two customers; F-79 is still in the warehouse.

Immediate actions: place R-118, M-501, M-502 and F-79 on hold, notify the two customers with the exact quantities and dates, and inspect retained samples. With a connected genealogy this takes minutes. With spreadsheets and paper travellers it can take days, while suspect stock keeps moving.

Running a mock recall

• Pick a raw material lot at random, without warning the team.
• Start a timer and trace forward to every finished lot and customer shipment.
• Reconcile quantities: received, consumed, scrapped, in stock and shipped should balance.
• Record the time taken and any gaps, such as missing links or unrecorded rework.
• Repeat backward from a finished lot.
• Set a target time and repeat the exercise regularly. Many customers and food safety schemes expect this as a periodic test.

Common traceability gaps

• Rework and regrind that re-enter production without a lot link.
• Partial lots split across work orders.
• Supplier lot numbers not captured at receiving.
• Lot numbers typed by hand with inconsistent formats. Barcode scanning solves most of this.

Lot numbering and labelling

A good lot number is unique, machine-readable and meaningless enough that nobody is tempted to reuse it. Encoding the date or line into the number is fine for human convenience, but the system should never depend on parsing it. Print lot numbers as a barcode or QR code on travellers, containers and finished-goods labels so they are scanned rather than typed.

Record the link between lots at the moment of consumption, not at the end of the shift. If an operator loads a new coil, bag or reel, scanning its label at the machine is the most reliable way to create the genealogy link. When material is split, merged or reworked, create a new lot with links to every parent so the chain stays intact.

• One lot number format across all plants and systems.
• Scan at receiving, at each consumption point and at shipping.
• Never relabel a lot without recording the old and new identifiers.
• Keep retained samples for critical lots where the product allows it.

Traceability in QCIN

QCIN stores lots, lot links, supplier lots with certificates of analysis and shipments, and shows a visual forward and backward genealogy with recall impact. A suspect lot and everything made from it can be put on hold in one action.