---
description: Model discrete production on automated and manual Lines with unit-level tracking from the first to the last station.
alias: userguide-modellingguides-unittracking
---

# Line processing with Unit Tracking

Industrial Equipment manufacturers frequently run production on fully or partially automated lines, where a product is assembled or processed across a sequence of dedicated stations rather than at a single work center. In several of these use cases — such as small motor, pump, actuator, or gearbox assembly — unit-level tracking is required throughout the line, so that each individual unit can be traced from its creation at the first station to its completion at the last, even as it moves automatically from station to station at high frequency. This guide describes the base model approach for these Line scenarios.

## Overview

This modeling guide proposes a base model approach for discrete production on a Line with unit tracking, on a scenario where all pieces are produced individually at each station (Sub Resource).

Unit tracking for the entire process is required, including inside each step of the line. When automation is used to receive signals, serialization and unit tracking are controlled by automation. For manual lines, MES is responsible for the operation triggering along with the serialization.

**Note**
>   This guide covers both fully/partially automated lines and manual lines, as there are scenarios where part of the production is automated with manual steps in between, requiring both approaches to be supported on the same model.

## Business Context

The industry setting provide us with business use cases that require more specific modeling approaches due to the level of automatization and processing cadence.

The Production Order is tracked on the shop floor operations through the Materials that compose them. All production context are Production Order specific, including the BOM, Recipe, and routing definitions.

Key points of this scenario:

- Fully automatic line or automatic/manual line.
- Serialized product, unique material ID (Physical/digital reference part number) created early in the line and identifying the asset.
- All assembly steps performed inside the line, across multiple stations.
- Machine-frequency processing, driven by machine cycle time rather than operator pace.

This model approach is not intended for very high-volume processes (e.g. more than 1000 units per batch) or high-throughput processes requiring execution times below 2 seconds per unit or processing steps.
In such scenarios, a map-based model would be more suitable.

For this Automatic Line scenario, we will consider that production is controlled by a Production Order. In MES there are already line-level context definitions for the BOM, Recipe, and Flow (Routing):

- **BOM** – Main BOM configured at line level, with the consumption Steps defined for all the stations within the line.
- **Recipe** – Recipe configured at line level, with sub-Recipes for the stations if needed.
- **Flow** – Line Flow model with the main Step representing the line and sub-Steps representing each station.

**Material Processing** - The processing of Materials on the line happens at two different levels:

- At a higher level, the processing of the *Production Order* **Main/Batch Material** that represents the Production Order demand.
- At a lower level, the processing of the *Production Order* **Unit/Sub-Material** inside the line that are tied to the running Production Order Main Material.

These two levels of manufacturing tracking can be summarized as:

**Processing of the Main Material, at the top-level step:**

- Main material start represents the start of production on the line.
- Main material is maintained In Process until all the individual Sub-Materials are processed.
- Main material stop represents the end of production on the line.

**Processing of the Sub-Materials on each station of the line:**

- Main Materials are *expanded* which creates Sub-Materials that represent the material unit on the line.
- Sub-Material Track In and Track Out are used to process the units on different stations.
- Sub-Material rework is supported when required.

## MES Modeling

The modeling for this Line is based on the Line Flows model.

The following considerations should be taken into account when modeling as a Line-Flow:

- **Pros:** more accurate representation of the line digital twin – line structure, materials movement, material consumption. Production control at Main Material level.
- **Cons:** a Line Flow modeling approach has some restrictions on the use of certain out-of-the-box functionalities (e.g. Future Actions, Inspection).

Modeling key points:

- The production line is represented as a main Step with sub-Steps.
    - The main Step represents the line itself.
    - Each station/operation is modeled by a sub-Step.
    - Each sub-Step can have one or more process Resources (in the case of parallel stations).
- Consumable Feeds are modeled at sub-Step level – BOM consumption is tracked at each Station.
- Rework stations are modeled in MES as an Off Flow, to which Materials are sent when required.
![AutomaticAndProcessLineDiagram](modellingguides.images/AutomaticAndProcessLineDiagram.png)
### Process Walkthrough

1. Operator triggers Main Material Track-In
     - The operator triggers the line Start by selecting a *Main Material* in MES and performing Track In.
2. MES EI receives Line Processing signals / Operator performs Expand, Track In and Track Out on the sub-Materials
     - Operations for each unit per station.
     - Each Unit Load signal creates a Material in MES that represents a physical unit on the line. This creation is performed by the Expand operation of the *Main material* (which can also be performed on the UI in a manual scenario).
     - Each Sub-Material then receives Unit In and Unit Out signals, to perform Track In and Track Out on each station. Track In and Track Out can also be performed on the UI in manual scenarios.
3. MES EI receives Line rework signals / Operator performs rework operation
     - In case the Line automation registers a faulty material, a signal is raised to MES EI.
     - The sub-Material goes to the rework flow.
4. MES EI receives completion signal / Operator performs Track Out of the last *Sub Material* on the last sub-step of the line.
     - The *Main material* performs Track Out and becomes processed on the main step.

The production information can reach MES in different ways. Lines with the capability to provide shop floor signals can be used to automate MES operations, allowing MES to gather process information through the IoT layer. We split the processing types into two groups:

- **Lines with automation (or partial automation)** – The process information is sent to MES, and MES automatically performs Material operations based on machine signals.
- **Manual lines** – Operators interact with MES to record the physical process on the shop floor using MES operations on the UI.

### Full/Partial Automated Line

This type of production line ensures material traceability by tracking the location of materials at any given moment. MES can provide unit tracking when the line stations can generate entry and exit events for materials — allowing MES to follow the path of individual units through the various machines in the line — achieving Unit Tracking, which offers traceability at the unit level.

This approach of ingesting information from machine signals implies that the line pace generates signals at a speed that allows the automation layer to trigger MES material operations in a timely manner.

The implementation of the integration between IoT and the line needs to be in sync with the MES model. The approach to these scenarios involves having a main Resource that represents the production line itself, where all Main Material operations are carried out, along with sub-Resources representing each station where individual Sub-Materials are processed.

The signals received from the line can be divided according to their granularity – Main Material operations or Sub-Material operations.

**Line controller signals related to Main Material operations:**

- **Order Start** – Signal that represents the start of production on the shop floor. This signal is normally tied to the Track In operation of the Main Material on the Resource that represents the line. The message is sent from MES to the equipment with information about the order and all relevant production parameters for the line and each of the stations.
- **Recipe Download** – The machine is informed of the production parameters it needs to use through a Recipe, sent from MES to IoT and then to the line controller. The line controller is responsible for spreading the different recipe parameters among the stations.
- **Order Abort** – Represents the stoppage of production of an order before it reached the target quantity to be produced. This operation can be triggered either from MES or from the line controller. After an abort, the state of the Main Material is reset to Queued, allowing operators to restart production.
- **Order Complete** – Represents the completion of the production order. After completion, the state of the Main Material is changed to Processed and the state of the Production Order is changed to Completed, representing that it finished the process on that line.

**Line controller signals for each station related to Sub-Material operations:**

- **Unit Load** – Tied to the creation of the Material that represents the physical unit on the line. To keep the link between the unique piece and the running Main Material, the Material is created as a Sub Material of the Main Material, using the out-of-the-box Expand operation.
- **Unit In** – Represents the start of processing of a Sub-Material on a station. In MES, this signal is handled using the Track In operation of the Sub Material (physical unit) on the Sub Resource (station).
- **Unit Out** – Represents the end of processing of a Sub-Material on a station, meaning the Track Out operation on the Sub Resource, in MES terms.
- **Unit Error** – When processing on a station fails for some reason, a Unit Error signal can be raised and handled differently according to the error. The Material can be either terminated or sent to a rework station.

### Manual Lines

Production lines that operate in offline mode do not provide any shop floor data regarding the materials being processed at any given moment — neither at the production line level nor at the level of the individual machines. For this type of line, all MES-level processes are handled entirely by operators through graphical user interfaces. Manually performing the operations on MES is generally only viable for low volume, slower-paced processes. 
For high-throughput volume, a different MES modeling approach should be adopted to ensure efficient material tracking without adding unnecessary actions or complexity to the operator workflow.

**Note**
>    Even for lines that allow automation integration, when the automation behavior is deactivated — either for the full line or for specific stations — operators need to manually perform the operations in MES.