Bill of Materials (BOM)

What is a Bill of Materials?

A Bill of Materials (BOM) is a list of the raw materials, sub-assemblies, sub-components, parts, and the required quantities to assemble, construct, manufacture, and repair a desired end product.

Bills of materials are often associated with a corresponding production or work order, especially if using a work instruction platform. When the work order comes down the line, manufacturing operators have a list of the materials they need along with the instructions to manufacture the product.

Due to their strong association with work/production orders, BOMs are a strong means of communication within a facility and between partnering companies regarding the requirements and usage of materials.

How to Structure Your BOMs

There are numerous ways to structure your BOMs. But before we get into the weeds of the different structures that companies and departments will use, there are a few simple guidelines that most BOMs should follow.

• Create a hierarchical structure: A good rule of thumb is to structure your bills of materials in a hierarchical view. The finished product goes at the top, the base components are in the middle, and the base materials rest at the bottom.
• Give each item a clear name: Workers should be able to quickly identify every part or material by a detailed and comprehensive name.
• Give each item in the list a numerical value: Every item should have a unique part number. A serialized part number allows for better verification and tracking of the materials and helps to mitigate miscommunications.
• Qualify the quantity and units of measure: BOMs need to be specific, especially if you are tracking inventory through an ERP. The number of materials types used along with the specific size of each component are invaluable metrics to keep track of.

2 Types of Bills of Materials: EBOM vs MBOM

There are 2 main types of BOMs that are extensively used within the industrial environment. These are the Engineering Bill of Materials (EBOM) and the Manufacturing Bill of Materials (MBOM). Each material list has key strengths that are beneficial to a specific type of user and department.

Engineering Bill of Materials (EBOM)

Engineering Bills of Materials (EBOM) are like a master list of materials and components. Generally, these lists are created using 3D drawings, such as CAD models, that specify the part numbers, quantities, measurements, and supplementary engineering notes on each component.

EBOMs include product code, part name & number, part description, quantity, size, length, weight, and additional features.

Some engineering bills of materials will also list the known alternatives and substitutions that can be used to fabricate or assemble the product within specifications. This level of specificity is what sets this BOM on a level of its own. However, one could argue that it provides too much information for workers who build the product on the shop floor.

Manufacturing Bif of Materials (MBOM)

Although very similar to an EBOM, Manufacturing Bills of Materials (MBOM) are less concerned about how the product is designed and more concerned about the parts that are needed to assemble the product. List items like alternatives and substitutions are not typically found in an MBOM. This shift in focus allows MBOMs to get straight to the point and be more useful on a manufacturing floor.

MBOMs are comprised of pertinent information regarding the assembly and completion of the end product while also detailing how the parts relate to each other.

Additionally, MBOMs often list the packaging materials that enable the product to be sent to the customer, which EBOMs do not typically have.

BOMs and Work Instruction Software

While BOMs give engineers and manufacturing operators the key parts and materials required to create a product, they lack in-depth instructions on how to build them.

Imagine a cake recipe. The ingredient list is insurmountably important. Without it, your ingredient ratios will be off, affecting the taste and texture. But you also need a detailed process to mitigate adding ingredients at the wrong time or in the wrong order.

While BOMs hold much more information than a typical cake ingredient list, they do not provide a complete picture or all the required information to build the end product. The process and the ingredient/materials list need to be mapped out together into a single operation.

Detailed digital work instructions have a BOM list embedded into every process and procedure. The BOM list is automatically retrieved from your ERP, MRP or MES and pushed to the work instructions through our advanced API. Users can then review the always-up-to-date BOM list at any point in the procedure.

BOM integration with digital instructions enables companies to seamlessly review, track, and organize material usage and requirements for every product. At the same time, manufacturing operators and engineers receive a comprehensive procedural guide that leaves nothing to chance, giving every worker the right information at the right time.