Manufacturing
The batch you decide yourselves
The line does not stop, so the batch is not set by the product: you set it. And its width is what it will cost the day something goes wrong.
Your line runs without interruption for whole shifts. There is no piece, no unit, nothing you can pick up and call «this one». **The batch is a convention: somebody decided a batch is eight hours, or a silo, or a day** — and that decision, taken years ago for probably operational reasons, is what will determine how much product has to be touched the day a problem appears.
What changes depending on where you draw the line
| Batch width | Daily cost | Cost on the bad day |
|---|---|---|
| One shift | More records | Contained to one shift |
| One day | Fewer records | Contained to one day |
| One week | Almost none | **A week of production** |
| **Undefined** | **None** | **Everything out there** |
Important
**Batch width is an economic decision dressed as a technical one, and it is almost never taken looking at the scenario that matters.** It gets chosen for production convenience —what fits the shifts, the silos, the system— rather than by the question that should decide it: if something has to be isolated tomorrow, how much product do I want to be forced to touch? That question costs one meeting and is answered once.
What must be reconstructable for each batch
- 1
What went in: raw materials and their consignments
If the output batch cannot be tied to the input ones, it traces nothing.
- 2
What conditions applied while producing
The readings you already take, tied to the batch rather than the day.
- 3
Where it went: what shipped and to whom
It is the half that almost always lives in another system.
- 4
And what was changed mid-run
A mid-shift adjustment splits the batch in fact, if not on paper.
Watch out
The structural failure in this position is **that traceability breaks exactly at the system boundary**: production knows what was made and logistics knows what was shipped, but the batch and the delivery note live in different places and nobody has ever tied them together. While nothing happens, it does not show. The day you have to decide who to warn, that seam is precisely where everything tears, and rebuilding it by hand takes days you do not have.
Worth knowing
How a batch must be defined for your product, what records must be kept and for how long, and what your certification scheme requires **depends on the product and the applicable scheme, and is settled by your adviser or certification body**. Here we cover the organisational part: how to tie inputs, conditions and outputs to the same unit so scope can be contained when needed.
›Is a narrower batch always better?
It is dearer daily and far cheaper on the bad day. It is a decision, not a given.
›Can I change the batch definition?
Yes, and it is worth revisiting. What does not work is having one nobody ever thought about.
›What use is tracing if I cannot identify the product physically?
Containment. Without physical identification, records are the only thing that narrows scope.
A real case
The situation
A problem must be contained and the batch spans a whole week.
What you do
- Allows recording per unit rather than only per day
What you get
Scope narrows to what is actually affected.
The situation
Production and dispatch live in different systems.
What you do
- Gathers what was made and what shipped in one file
What you get
The batch can be followed through to the customer.
The situation
Shift readings are filed by day rather than by batch.
What you do
- Ties each record to the unit that traces
What you get
Conditions are consulted per batch.
The situation
A mid-shift adjustment is not reflected anywhere.
What you do
- Records changes with their time inside the batch
What you get
The real split of the batch is known.
The situation
A customer asks about a consignment delivered a year ago.
What you do
- Keeps the batch file with its date
What you get
It is answered without reconstructing anything.
The situation
Nobody knows which raw materials went into a given batch.
What you do
- Ties input consignments to the output batch
What you get
Tracing runs backwards and not only forwards.
This article answers
- how to define a batch in continuous production
- what batch width is reasonable
- traceability in continuous manufacturing
- how much product would i have to recall