Why a lot number on its own is not traceability
Most systems can print a lot number. Far fewer can answer the two questions that
matter when something goes wrong, and they are opposite questions.
Backward: this finished lot is suspect. What went into it?
Forward: this ingredient lot is suspect. Where did it end up?
Answering only one of them still leaves you recalling by date range. Lot genealogy
is the linked record that answers both, and it has to be built while production
happens, because it cannot be reconstructed afterwards.
The chain
Each step consumes specific lots and produces a new one that remembers them.
- Receipt. A delivery becomes a lot with a supplier, a received date, an
optional expiry, and the unit cost you actually paid.
- Production. A batch consumes specific component lots. The finished lot
records which ones and in what quantity, not just the recipe.
- Allocation. An order draws from a specific finished lot, which is the link
between what you made and who received it.
Break any one of those links and the trace stops there. The usual break is step
two: a system that deducts "10 kg of sugar" from a pooled figure rather than
"6 kg from lot A and 4 kg from lot B" has lost the genealogy at the first
operation, no matter how carefully the lot numbers were recorded on paper.
Transformation is the hard part
Traceability is easy while stock sits still. It gets hard when one thing becomes
another. A batch that is consumed into a second batch has to carry its ancestry
forward, or the chain resets and the finished good points back only as far as the
intermediate.
This is where multi-level production usually loses the thread. A semi-finished
subassembly is both an output and an input, and it needs to be both in the record.
What it changes in a recall
Without genealogy, scope is defined by time: everything made in the window when
the suspect material could have been used. With it, scope is defined by fact: the
batches that actually consumed the suspect lot, and the orders that actually
shipped them.
The difference is usually an order of magnitude in product withdrawn, and the
larger number is not the safer one. Recalling product that was never affected
costs the same money and buys no additional safety.
In IEMSuite
Every unit of stock belongs to a lot, and there is no mode that turns that off,
because allocation, QC and costing are all built on it. Production consumes
specific lots by FIFO or FEFO and the finished lot inherits their genealogy.
Movements are append-only, so history cannot be edited after the fact.
FAQ
How far back should genealogy go?
To the supplier receipt. If the chain ends at your own goods-in, you can bound an
internal problem but not a supplier one, and supplier problems are the common case.
Does this work with multi-level BOMs?
Yes. A subassembly is a production batch that becomes an input to another batch,
so the ancestry chains through each level rather than resetting.
What if I merge two lots of the same material?
Then the merged stock has two ancestors and any trace from it widens to include
both. Merging is sometimes unavoidable, but it is worth knowing that each merge
permanently widens every future recall that touches the result.