Lot traceability in manufacturing: tracking batches and heat numbers

What lot traceability is

Traceability is a question in two directions. Looking backward, you ask what went into this part and how it was made. Looking forward, you ask where this batch of material went. Both answers come from records that were linked together while the work was done:

The basic rule is often called "one up, one down". If every step records what came in and what went out, the whole chain can be rebuilt end to end.

Why it matters

• Complaints and recalls depend on it. When a supplier reports a bad heat, the question is "which parts, which customers?" Without traceability the answer is "everything we made that month". With it, the answer is only the lots made from that heat.
• Customers ask for it. Aerospace, automotive, medical and food packaging customers want material certificates and batch information with each shipment, and in audits they want to follow the chain backward from a part.
• It helps with root cause analysis. When a lot turns out bad, knowing which machine, which shift and which inspections it went through tells you whether the problem was the material or the process.
• Digital product passports are on the way. The European Union is introducing them for product groups one by one, and large buyers already ask suppliers for material origin, energy and carbon figures. Those come from the same lot records.

How shops do it today

In most job shops, traceability is spread across a few papers and files:

• The heat number is written on the delivery note or in a goods-in book at receiving. The certificate PDF stays in an email or a shared folder.
• The operator notes which bar they cut from in the corner of the traveler, which comes back to the office when the job is done, or doesn't.
• The shipping paperwork says which lot went to which customer, but which heat that lot was made from is somewhere else.
• In a recall, someone lays all of these side by side and tries to rebuild the chain by hand, which usually takes days.

The information usually exists somewhere. The trouble is that the records are not linked, and cannot be found when they are needed.

How to set up traceability well

1. Record material at receiving. Supplier, heat or batch number, quantity, date received and certificate belong in one record. Hunting for the certificate later is where most of the time goes.
2. Keep the heat number on the material. Write it on the bar, the sheet edge or the box, and make sure an offcut going back to the rack still carries it.
3. Decide what a lot is. In most shops it is the output of one work order, or one shipment. Bigger lots mean less recording, but more parts caught up in a recall.
4. Link inputs at the step that consumes them. Which lot or work order a material went into should be recorded on the day it is cut or used, not remembered at the end of the week.
5. Link sub-lots in assemblies. A machine or a mold is built from components with their own lot numbers. The chain only reaches the raw material if those links exist.
6. Label the lot. The lot number belongs on the part, the bin or the package. Without a label, a part in the field cannot be matched to its record.
7. Run a mock recall once or twice a year. Pick a heat at random and list the customers it reached. How long it takes tells you how well your system works.

Common mistakes

• Defining lots only at shipping. The package then has a number, but nothing says which heats are inside.
• Mixing two heats in one lot without recording it. A bar runs out mid-job and the next one is from a different heat, so both inputs need recording.
• Leaving offcuts unmarked. A half bar goes back on the rack, is used on another job months later, and the chain breaks there.
• Leaving certificates in email. When an auditor or a customer asks, the file cannot be found.
• Filling everything in afterwards. Records typed from memory at the end of the day are wrong exactly when they matter most.

How lot traceability works in ModernMES

In the ModernMES panel, the Traceability screen has three tabs: material lots, production lots, and lot and emission settings. The flow has three steps.

1. Record material when it arrives. Enter the material code and name, supplier, batch or heat number, country of origin, quantity and unit, date received, and certificate type and number. The certificate file (a PDF or an image) is uploaded on the material lot's page after saving. Material lots can be searched by material, heat number, supplier or certificate number.
2. Open a lot when the job is done. A production lot is created from the lot card on the work order's page, or with "New lot", and all steps of the part come pre-selected. If you leave the number empty, the next one in your own series is assigned, for example LOT-00001. You can add serial numbers to a lot, and lots can be found by serial number. A lot is open, released, blocked or shipped.
3. Record what went into it. Pick the material lot that went into the lot or the work order and the quantity used. In assemblies, component lots are added the same way. You cannot use more than what is left in a material lot, and a lot cannot be added as an input to a lot that was made from it.

From then on, both directions are one click away:

The backward chain and the recall list download as CSV files that open in Excel. Lot labels print in batches, with the lot number, part, quantity, production date and the QR code of the product passport.

A few things to know. Material and consumption records are entered in the panel by users with the admin or manager role, and the operator terminal has no traceability screen. Machines, operators, inspections and scrap come from the work order on their own. A material lot shows how much was used and how much is left, but ModernMES is not a full inventory or warehouse system today.

Product passport, energy and carbon estimates

Every production lot can have a public product passport page, opened by the QR code on its label. A passport stays off until you publish it, and while it is off the link answers "not found". The page always shows the part code and name, lot number, quantity and production date. You turn on the other sections one by one:

• Company legal name, city and country
• Material origin, meaning material name, batch or heat number and country of origin
• Supplier names (hidden by default)
• Certificate type and number. The file itself opens only if the material lot marks it as shareable
• Inspection summary, with how many checks were made and how many passed, by type
• Energy and carbon estimates
• Serial numbers (hidden by default)

Customer names, operator names and internal numbers never appear on a passport. You can replace the link. The old link and the QR codes on labels already printed then stop working.

The energy estimate is each machine's rated power (kW, from the machine record) multiplied by the time the job actually ran on it. Pauses are not counted. Run time on machines with no power rating is left out of the energy figure and flagged on screen. When one work order is split into several lots, its energy is shared out by quantity.

Carbon is calculated only once you enter a grid emission factor (kg CO₂e per kWh) together with its source, and the factor is shown with that source wherever it is used. Without it, no carbon figure is shown anywhere. You can also enter a factor in kg CO₂e per kg for each material code. It applies only to material inputs in a mass unit (kg, g, t). Carbon from component lots is carried into the assembly lot. The Energy report (CSV) gives kWh, kg CO₂e and the factors used for every lot produced in a date range.

These are estimates made from figures you enter. They are not a certified declaration (such as for CBAM) and do not make a product compliant with any regulation.

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