Digital Thread: The backbone of end-to-end product development

The digital thread connects the elements of a product throughout its entire life cycle. Without this digital thread, true product velocity is not possible. But what exactly is it? Qiang Zhang and his colleagues have systematically addressed this question and conducted a comprehensive literature review. Of particular interest to readers: the relationship to MBSE, PLM and the digital twin.

The paper

The paper with the title A Literature Review of the Digital Thread: Definition, Key Technologies, and Applications was founded in 2024 by Qiang Zhang, Jihong Liu and Xu Chen at the Beihang University and appeared in the journal Systems (Vol. 12, Issue 3). It is based on the analysis of 94 scientific articles between 2015 and 2023 and provides a comprehensive view of the definition, core technologies and applications of the Digital Thread.

What is the Digital Thread?

The term was coined by the United States Air Force in 2013. The original idea was to enable a continuous digital data flow from the finished component to the model. The focus here was on production. For example, 3D CAD data was to flow directly into the CNC machines, thus enabling seamless traceability. This resulted in a comprehensive concept for the digital integration of all data across the entire life cycle of a system.

Definition: The Digital Thread is an end-to-end, digital information flow that connects all relevant data, models and decisions across the entire life cycle of a product, makes them traceable and keeps them available in real time.

Despite different formulations in the literature, three central aspects can be identified (the original term from the paper is in brackets):

• Authoritative data (authoritative data): This refers to a reliable, consistent and recognized data source that serves as the authoritative reference for all decisions in the product life cycle. This data source must be up-to-date, complete and consistent. It replaces fragmented individual data and enables standardized work across disciplines and systems.
• Data linking (Data Linkage): The ability to connect data across system, process and lifecycle phases. Only through clean Traceability ensures the consistency of requirements, models, tests and operating data. Data linkage is therefore a prerequisite for traceability, change management and compliance.
• Model integration (Model Integration): The technical and semantic linking of different models and tools from disciplines such as systems engineering, mechanics, electronics, software, simulation and production. The aim is to achieve a consistency that avoids breaks in information and allows a holistic view of the system.

The digital thread therefore ensures that there is a "single source of truth" for every piece of information. It is therefore more of a digital backbone than a thread that holds all models, information and decisions together.

The digital thread is less than 10 years old

In 2017, there were only 17 scientific papers on the digital thread. In 2018, the number almost exploded to 90, and interest continued to grow exponentially in the following years. By 2022, there were already over 250 publications. The focus of research was strongly on applications in manufacturing. Product development, as well as operations and logistics, are underrepresented.

Relationship with the Digital Twin

The digital thread is often associated with the concept of Digital Twin confused or mixed up. The relationship is as follows: The digital thread is the foundation on which digital twins are built. It ensures the bidirectional connection between the physical system and the digital twin, enables consistent updates, allows traceability and provides a uniform view of the product and process.

Relationship with MBSE

MBSE often serves as an entry point for the digital thread. While MBSE usually takes effect in the early phase of system development, the digital thread connects these models with later phases such as production, operation and maintenance. MBSE provides the language (e.g. SysML), the digital thread ensures the use, maintenance and integration of the models across the life cycle

The Digital Thread is actually the logical realization of the SYSMOD Intensity ModelAt the lowest level, the models are merely communication tools; at the end, they represent a living specification. The goal is the transformation from document-centered to model-based and ultimately to data-driven engineering.

Relationship with PLM

Product Lifecycle Management (PLM) is established in many companies, but usually focuses on production data. The digital thread extends PLM to include the ability to connect and use heterogeneous data sources consistently across the entire life cycle. Modern PLM systems such as Siemens Teamcenter deliberately use the term digital thread to suggest consistency.

Application

At the moment, the term digital thread is primarily used in production, particularly in the aerospace industry. We also find the term for consistency in 3D printing (additive manufacturing), where the thread runs from component geometry to machine data to in-situ sensor technology. The aim is a transparent, traceable and quality-assured manufacturing process.

The authors mention specific companies such as Lockheed Martin, Airbus and Boeing, which are already using the digital thread to optimize assembly processes, for traceability and for predictive maintenance. Small companies are also implementing parts of the digital thread with the help of inexpensive tools such as Modelica or Node-RED. Companies like to use the OPC Unified Architecture (UA).

Implementation

The introduction of a digital thread requires a rethink and goes far beyond the introduction of tools. Teams need to build up specific skills and ensure that the digital thread does not become an end in itself. This also means, for example, that the company has an understanding of MBSE and is already using modeling successfully.

Successful deployment requires interdisciplinary thinking, technical expertise and organizational change. This is the only way to realize the potential of the digital thread in terms of quality, speed and innovation.

Conclusion

The digital thread is a relatively new concept that plays a major role in the transformation of digital product development and manufacturing. I personally see it as an important part of Product Velocitya topic on which I am working on a book.