eBOM vs. mBOM vs. sBOM: Strengthening the Digital Thread

In our last entry to this blog series, we explained the strategic imperative for modern manufacturers to implement a holistic, parts-driven BOM management strategy. The complexities companies face in bringing great products to market quickly, at scale, and with uncompromised quality include not only dynamic market forces, but legacy systems and heterogeneous data generated at different nodes of the production operation.

Today, product lifecycle management has evolved into a shared enterprise initiative, requiring seamless coordination and collaboration between all upstream and downstream constituents. Universal, self-service access is the objective, and the different BOM structures – eBOM, mBOM and sBOM – must always resolve into a holistic, coherent record of the product. That record, always current and accessible in real time, unifies the enterprise both inside and outside of the core product development team.

What is Bill of Materials Management?

Bill of materials (BOM) management is the capturing, configuring, and managing of all product data that is developed throughout the lifecycle of a product within the hierarchical structure of a BOM. The diversity and scope of data managed in the BOM will range depending on the product in question, but can include anything from raw material specifications, embedded software details, electronic and mechanical components with their drawings and models, product requirements, preferred suppliers, regulatory compliance, and more.

Given the potential enormity and complexity of data that can be house in a BOM, having the appropriate tools and processes to manage each change and communicate BOM data to stakeholders along the product lifecycle is critical to ensuring quality, cost, time-to-market and other key operation metrics downstream.

eBOM, mBOM and sBOM: The Functional Need for Unique Bills of Material

Regardless of the existence of a “master” bill of materials – a complete register of the materials, quantities and items required to manufacture the product – different teams rely on more specific BOM iterations. While each BOM type serves the same product, they can be very distinct in the detail and content. 

Digital Thread: The Critical Tie that Binds (the eBOM, mBOM and sBOM)

Acknowledging that these phase-specific distinctions are functionally critical to the success of each lifecycle stage and by extension the overall process, the discrete BOMs must be consistent among one another - tightly linked and perfectly aligned. Unless every substantive change made by any party, at any point in the product’s lifecycle, is accurately propagated, with timely notification to every involved stakeholder, manufacturers run an increasing risk of expensive errors and delays.

But when eBOM, mBOM and sBOM structures BOM are synched in real time via the digital thread, together they generate (or, if that’s too strong, consider “critically inform”) a single source of truth by which the product is defined. Without that basis for bedrock product governance, the volume and variety of data involved can obscure, rather than clarify, that truth. As each type of BOM structure contributes to, and draws from, this source, it’s important first to understand the distinctions between them.

Here is an example of how this digital thread can work in practice:

When PTC’s BOM transformation technology in Windchill transforms an upstream eBOM to a newly structured downstream BOM (mBOM or sBOM) it also creates an equivalence link for each part that constitutes the BOMs. The most important feature of this transformation is maintaining traceability of every occurrence of each part and the 3D position information of each part geometry.

Among the many benefits of this linkage is the ability to easily create and maintain product visualization in downstream documents that rely on these derivative BOMs even as upstream changes are made to the eBOM. This ensures that vital resources like manufacturing process plans, service parts lists, maintenance instructions, and even augmented reality experiences are always in synch with the product definition and each other.

What Is the Difference Between Engineering BOM (EBOM), Manufacturing BOM (MBOM), and Service BOM (SBOM)?

The eBOM: Engineering Details

The engineering bill of materials (eBOM) defines the product as designed. Initially generated during the design phase, the EBOM is created automatically by engineering and design software, such as CAD or EDA tools. It defines in comprehensive detail the component items, parts, assemblies and sub-assemblies which collectively capture the design engineering team’s vision. The EBOM includes highly detailed engineering information like required standards, material tolerances, and product specs.

It’s important to note that a given product may involve more than one EBOM. An individual component, like a printed circuit board or a robotic arm, may have its own EBOM which nests within the larger bill-of-materials system. Every detail is crucial, of course, but the inherent impact on overall complexity is obvious, and fuels the need for a single source of truth as discussed above.

The MBOM: Building the Perfect Product

As distinct from the EBOM, which is organized according to the product’s design requirements, the manufacturing bill of materials (MBOM) defines and supports how a product will be assembled. It describes all the parts, assemblies, and components needed to actually build the product and ready it for shipment. It may specify the machinery needed to complete production, process steps, and packaging requirements.

Only a properly developed and well-integrated MBOM can ensure that the goods emerging from the production line match the intent of the design team. If the MBOM is not perfectly synched with the EBOM, products may be manufactured incorrectly, and the production process burdened by unexpected delays, rework, and material waste.

The SBOM: Extending the Product's Useful Lifecycle

Post-production, customers, field service teams, service contractors and other providers need to maintain and extend the product’s useful lifecycle. The service bill-of-materials (SBOM) addresses all the serviceable parts of a product, or the components that could otherwise affect its serviceability. The SBOM addresses considerations specific to the useful phase of the product’s lifecycle. Only after the product is in-market can it fulfill the vision of its designers and manufacturers, and to do so effectively the SBOM must fulfill discrete and critical functions: 

• Create a foundation for service processes that’s up-to-date, accurate and easy to use
• Organize product information in a way that’s intuitive for service stakeholders
• Update the parts catalog whenever changes are made to the product or its serviceable components anywhere in the BOM system

How Do the EBOM, MBOM and SBOM Work Together?

Regardless of the distinctions between BOM types, they all must mesh to result in a product that meets its designers’ expectations, can be manufactured accurately and well, and serves its end users’ needs over as long and useful lifecycle as possible. When the BOMs are properly connected and synthesized, easy, real-time access to every detail, by whomever needs it, drives manufacturing effectiveness and improves quality, while minimizing downtime and reducing production errors. Inventory management is streamlined, and re-work and material waste reduced or eliminated.

A well-managed and unified BOM is indispensable to the enterprise’s overall business objectives. Where thousands of components, hundreds of tasks and many disciplines are involved, it keeps often widely dispersed teams aligned by propagating changes across and between departments. Ultimately, it’s only through effective, integrated management of the discrete BOM types that the product envisioned in design can achieve its full promise in the field, yielding all the benefits – to customers, end-users and shareholders – that the business was built to deliver.