BOM 101: The four pillars of every BOM management solution

BOM 101: The four pillars of every BOM management solution

I suggest you an experiment. Invite two engineers and ask them to provide a definition for some of PDM/PLM related terms. I’d not be surprised if you will get more than two definitions. It is not unusual to spend lots of time during PLM software implementation meetings to define terms, language and meaning of things. Regardless on terminology, I found BOM to be a central element in every product development organization and business. It contains a recipe of your product, process and, at the end of the day, becomes a lifeblood of your product development processes. Thinking about BOM management solution, I can see four major things that need to be defined, discussed and clarified.

BOM and Part Lists

Bill of Materials (BOM) is a list of all items required to make a parent item. It includes components, raw materials and sub-assemblies. You may also include intermediate items identifying in-process elements to facilitate planning and other manufacturing processes. Depends on industry, people can call BOM differently. For example, in process industry, it can be called recipe or formula. Opposite to BOM, Part List is usually a term used to call a single level list for a specific level of assembly or sub-assembly.

Part Number 

This is one of the most tricky defined terms in a whole product development and BOM management story. Here is a short definition. Part Number (PN) is an unique identifier that identify a single object in bill of material. However, the trick is how to define object and how to keep it consistent with your processes. Assigning part numbers is often complicated and one of the most discussed topics. The traditional definition of FFF (Form, Fit and Function) helps to identify the right objects. Interchangeable parts, substitiute items, special parts – this is only a short list of issues that comes into the discussion around part numbering process.


Think about navigation system with the road between different places. Now imagine part numbers. Routing is a roadmap that defines the path of part numbers across manufacturing floor by specifying workstations and labor time associated with every station. Usually routing applied to manufactured parts or items.


Drawings represents a significant part of history and confusing engineering habits. Historically, drawing is the place where people put bill of materials for a product. It also solves the problem of Bill of Materials distribution in the company. At the same time, BOM on a drawing brings lots of disadvantages. In many situations, people don’t need drawing, but only need bill of materials and/or part list. Another point of confusion is numbering system. The discussion is about applying part numbers on drawings. In most of the situations, it represents the limitation of systems used for product development (PDM/PLM). To separate between Part Numbers and Document Numbers is the most reasonable ways to manage it, in my view.

What is my conclusion? Regardless of what systems you plan to use, I recommend you to have cross-department organizational discussion about these four pillars. Usually, it helps to understand product development processes. Engineering and manufacturing are two main organizations usually involved into BOM processes. To clarify terms will give you a tremendous value during PDM/PLM system implementation and integration with ERP. Just my thoughts…

Best, Oleg

Disclaimer: I’m co-founder and CEO of OpenBOM developing cloud-based bill of materials and inventory management tool for manufacturing companies, hardware startups, and supply chain. My opinion can be unintentionally biased.


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  • pnigam

    Hello Oleg,
    First of all, I follow your articles and I must say they are really informative !
    As you mentioned Routing as one of the 4 Pillars of BOM management, so what is the best practice for storing the routes? Whether it should be stored in PLM or only in ERP and MES systems?
    And in an enterprise environment with complex landscape do you think that MES and ERP can ever share a common Routing?

  • beyondplm

    Pnigam, this is a very good question! There are few situations when you will prefer to keep routings in PLM – when PLM is using for process planning on a shopfloor (large PLM vendors have this modules) and when the strategy is to have PLM as master data management for BOM. I’d not be trying to keep routing if PLM is only used for engineering BOM or manufacturing planning BOM. Very often PLM, MES and ERP are sharing BOM data and routing is one of the pieces. Usually it comes as a result of complex sync between multiple systems.

  • pnigam

    Thanks Oleg for your response !

    also I have another question related to BOM:
    Are there any thumb rules to create a BOM in terms of structure in order to have consistent and correct BOMs? Of course I understand that every organization will have to define their own BOM structures..based on their business case.

    Who in the organization creates and maintains the BOM? What are the required skill sets? I mean NPI/Product Engineering/R&D or who?

  • beyondplm

    Depends what BOM. Engineering BOM is mostly influenced by design and CAD data. However, this is also a place where engineering adds all relevant information. Planning BOM (sort of MBOM) is controlled by manufacturing people planning production. Cost BOM can be restructured to reflect total cost. As built BOM must reflect a precise information about product delivered to customer. Service BOM should include all relevant service Parts and exclude everything else, which is not relevant for service people. As you can see, different stages of product development are reflecting the way BOM is created

  • pnigam

    Thanks Oleg!

  • venkat

    Service bom is not consider in BOM formation this will affect after market

  • beyondplm

    Would you recommend to use PLM system to manage service BOM?