What is a BOM?
A Bill of Materials (BOM) is a complete list of the components, materials, and instructions needed to assemble a product, serving as a blueprint for manufacturing and product. Each item listed in the BOM comes with specific information, including part names, quantities, costs, and instructions on how they should be used or assembled. Typically, this information is outlined in a hierarchy, showing the finished product at the top and each of the parts and plans at the bottom.
As an example, imagine you need new dining chairs but don’t know a thing about buying or building them. A BOM would list all the parts required for assembling the chairs, including the legs, seats, upholstery, screws, and more. It would also tell you the quantity needed for each part, such as four legs and one seat. Additionally, in case you didn’t know what the leg of a chair looked like, it would provide specific details about each part, like its dimensions and what materials it’s made of. And finally, it would provide you with detailed assembly instructions, piece by piece.
While a BOM seems relatively simple for something like a chair, it can easily become more comprehensive as we get into industries like design, engineering, or manufacturing. This is why a well-structured BOM is essential for efficient production, as it ensures that all the necessary components are available, as well as helps companies better manage their inventory, estimate costs, identify any product issues, and avoid delays in production.
Why are BOMs important?
BOMs play a pivotal role in processes across several roles, including production, manufacturing, design, procurement, sales, purchasing, and inventory management. They serve as a comprehensive roadmap for teams to follow, listing all the necessary parts, materials, and components as well as the instructions required to assemble a product. Each team plays a different part in the production process, and having a comprehensive overview of each process allows for all-around success. Additionally, BOMs are essential to specific areas of the business, including:
Scheduling
With a clear understanding of what's needed and when, BOMs help production managers create realistic production schedules, allocate resources efficiently, and coordinate tasks effectively. They also allow you to anticipate potential bottlenecks or delays, giving you the chance to proactively address any red flags you catch while reviewing the BOM.
Budgeting
BOMs provide precise details about each item, such as part names, quantities, and unit costs. This level of clarity not only aids in efficient production, but also allows for accurate cost estimation, helping companies plan budgets and allocate resources effectively.
Inventory Management
BOMs are instrumental in managing inventory levels. By clearly outlining the quantities needed for each component, businesses can maintain optimal stock levels, preventing overstocking or shortages. This also minimizes holding costs and reduces the risk of obsolescence.
Quality Control
By providing a detailed list of all components and materials needed, BOMs ensure that each item is accounted for and correctly sourced, minimizing the likelihood of using low-quality or incorrect parts.
What information is included in a Bill of Materials?
Part Numbers & Names
Part numbers and names help you identify the different components listed in a BOM. Names provide descriptive information, such as “wood leg” while part numbers like "LEG-001" provide a unique identifier for each piece. Part numbers are also commonly referred to as product codes or SKUs, and allow for detailed planning, tracking, and ordering of each piece.
Part Description
In addition to the number and name of the part, a BOM should include a description for each as well. The description should detail the part’s size, material, measurements, and other specifications. There’s a chance some components could look alike, so these descriptions can help manufacturers correctly identify each piece for accurate production.
Quantities
Next to each part number, name, and description should be the quantities needed for each. Quantities are crucial to the production planning and execution, as they provide cost estimation, help track inventory, and prevent delays by ensuring you have enough materials from the start.
Unit Costs
Unit costs, in combination with quantities, are also essential to project planning and budgeting. Without unit costs, you wouldn’t be able to calculate the total cost of production, identify cost savings, or ensure profitability on the final product.
Availability
The availability of each component on your BOM indicates whether your item is in stock, needs to be ordered, or is on backorder or unavailable. If your final product needs a certain number of the same components, but those pieces aren’t available to order at the moment, it could cause a production delay. Knowing this ahead of time helps with production planning, allowing ample time to order parts that are needed.
How are BOMs structured and managed?
A well-structured BOM helps companies minimize supply chain risks and shortages, ensuring an effective manufacturing process. In this article we’ll outline two different types of BOM structures–Single Level and Multilevel–but be sure to check out our other article if you’re looking for a detailed overview of How to Structure an Effective Bill of Material (BOM).
Single Level Bill of Materials
A single-level BOM is a straightforward list that shows the final product and the parts needed to produce it. They work well for products with simple assembly, such as furniture manufacturing or basic electronics – a single-level BOM would work great for those chairs we were building earlier, for example.
As mentioned, BOMs are typically structured in a hierarchical format; for single-level BOMs, this includes two levels. First, we have the final product on the top level, then we have the parts and components listed out on the bottom level, funneling into the top level. This is because each individual piece of the final product is already assembled, and now all that’s left to do is put all the components together to build the final product. As a result, single-level BOMs are clear and easy-to-read, making them hard to be misinterpreted by production teams
Multilevel Bill of Materials
On the other hand, a multilevel BOM outlines various levels of components, subassemblies, and materials needed to manufacture a product. Unlike a single-level BOM that lists only the direct components required for the final product, a multi-level BOM includes sub-assemblies that break down into their own components. This means you have to build those components first, which then make up the final pieces needed to produce the end product. These BOMS are ideal for industries with complex, highly-detailed products, such as electronics, machinery, and automotive.
Viewing a multilevel BOM is similar to a single level, just with additional levels. At the top level, you still have the finished product, then you have a level of sub-assemblies, then you have levels of parts that make up each subassembly. This creates a tree-like flow chart structure, offering a comprehensive overview and understanding of the entire production process.
Types of BOMs
There are many types of BOMs based on the product being built and your industry. These are the three main types you’ll likely encounter, along with a few other less common ones.
Engineering Bill of Materials (EBOM)
EBOMs are documents used specifically in product design and development, outlining the entire product lifecycle from conception to production. In addition to typical elements such as the part names, part numbers, and subassemblies, EBOMs can include technical specifications, engineering drawings, and other product development details relating to design and engineering stages. Additionally, EBOMs help the design, engineering, and manufacturing teams better collaborate, ensuring that the product is created as it was designed to be.
Manufacturing Bill of Materials (MBOM)
MBOMs are a standard type of BOM, outlining the details needed to meet a scheduled product production. They provide instructions specific to manufacturing, including detailed information on quantities, assembly processes, and quality standards, along with component and subassembly requirements. An organized and accurate MBOM is vital to manufacturing operations, helping to minimize errors, reduce waste, and maintain high product quality standards.
Sales Bill of Materials (SBOM)
SBOMs concern the delivery of a product to a customer, including details of the sales order of the finished product and components as well as the pricing of the product. It includes the sales order for both the finished product and components. In addition to physical parts, it also outlines services, documentation, and any other elements that complete the customer’s order. An SBOM also allows sales teams to communicate their offerings, generate quotes, and meet customer expectations, essentially streamlining the sales process
Other types of BOMs
Configurable Bill of Materials
A type of BOM that allows for the customization of product parts to meet specific customer requirements.
Production Bill of Materials
A type of BOM focused on the finished product, including the components, production process, and assembly instructions.
Assembly Bill of Materials
A type of BOM that lists the assembly and subassembly items needed for product production.
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