What is a Bill of Materials (BOM)?
A Bill of Materials (BOM) is a detailed list of raw materials, components, and instructions needed to construct, manufacture, or repair a product or service. Typically structured in a hierarchical format, a BOM starts with the highest-level finished product and drills down to individual materials and components.
There are different types of BOMs. Engineering BOMs focus on the design process, while manufacturing BOMs are essential for the assembly process.
Why Understanding a BOM Is Crucial
A BOM serves as a centralized information source crucial for manufacturing a product. It includes a list of all required items and assembly instructions. Accurate BOMs ensure that parts are available when needed, which saves time and reduces operating costs. Inaccurate BOMs can halt production, increasing costs as you scramble to find parts or figure out assembly processes.
A BOM is not a one-size-fits-all document. Different projects and business needs dictate different types of BOMs, commonly used in engineering, design, operations, and manufacturing. Key for designing Enterprise Resource Planning (ERP) systems and Materials Requirement Planning (MRP).
Items typically included in a BOM are part numbers, part names, quantities, units of measurement, assembly references, method of parts creation, and supplementary notes.
Visualizing BOM: Different Display Types
A BOM can be visualized in an explosion display or an implosion display. An explosion display breaks down an assembly at the highest level into its individual components at the lowest level. Conversely, an implosion display links all basic parts to their higher-level assemblies.
Example: A computer’s components such as hard drives, memory panels, and processors are exploded. Each processor contains sub-components like arithmetic units and control units. Implosion displays consolidate these sub-components back to the processor and finally to the computer.
Types of Bills of Materials
A well-constructed BOM is critical for product assembly, ordering replacement parts, and future repairs. The two main kinds of BOMs are Engineering BOMs and Manufacturing BOMs.
Engineering BOM
An engineering BOM includes all parts and instructions needed to build a product, encompassing alternate and substitute parts. Each line includes product codes, part names, part numbers, revisions, quantities, units, sizes, weights, and other specifications or features. Engineers typically create this BOM from Computer-Aided Design (CAD) drawings. Multiple engineering BOMs can exist for a single product as part of Product Lifecycle Management (PLM).
Manufacturing BOM
A manufacturing BOM includes all necessary parts and assemblies required for product completion and shipping, including packaging. It comprises procedures to perform on the product, ensuring the storage of all details needed for manufacturing activities.
The Uses and Advantages of a BOM
A BOM clarifies the relationship between a finished product and its components. It’s indispensable for cost estimation, purchase planning, part availability, and preventing production delays.
Advantages of Using a BOM
- Streamlines manufacturing processes
- Reduces waste
- Identifies product vulnerabilities
- Mitigates material shortages or supply chain disruptions
Crafting Your Bill of Materials
When creating a BOM, ensure you include:
- Name of the product or assembly
- BOM level
- Raw materials (with quantities and unit measurements)
- Necessary sub-assemblies
- Part numbers, names, and descriptions
- Unit costs
- Quantities
The Bottom Line
A Bill of Materials is a cornerstone of engineering and manufacturing processes, providing a thorough list of all parts and materials required to build a product. An accurate BOM minimizes waste, streamlines production, and ensures part availability, helping companies efficiently manage operations and reduce costs.
Related Terms: Supply Chain Management, ERP, MRP, Lean Manufacturing, Inventory Management.
References
- U.S. National Library of Medicine-National Institute of Health. “Towards a Lifecycle Information Framework and Technology in Manufacturing”.
- Project Management Institute. “The WBS”.
