A bill of material list, also known as a BOM, is a comprehensive list of raw materials, components and parts that make up a product. BOMs are important for managing and streamlining manufacturing processes.
Sometimes referred to as an assembly component list, product structure or product recipe, the BOM is crucial for numerous manufacturing and supply chain processes including MRP, inventory planning and scheduling.
What is a Bill of Materials?
A bill of materials, or BOM, is a comprehensive, structured list of raw materials, parts, subassemblies, components, and assemblies needed to construct a finished product. It is also referred to as a production recipe, assembly component list, and material take-off in technical production drawings or Manufacturing Execution Systems (MES). A well-structured BOM centralizes information across engineering, manufacturing, sourcing, supply chain, and other departments and stakeholders.
There are different types of BOMs based on the purpose they serve. The Engineering Bill of Material (EBOM), for instance, defines the design of a product and includes alternative or substitute part numbers. It also contains drawing notes, and each BOM line specifies the item code, description, part number, unit of measure, and other related information.
A multilevel BOM, on the other hand, is a detailed breakdown of the components and raw materials that are required to construct an assembly, including the sub-assemblies and subcomponents necessary for a given level of manufacture. It is useful for product costing, planning purchases, estimating inventory levels, and avoiding shortages of critical parts in the event of a supply chain disruption. In the case of a multilevel BOM, each individual component or sub-assembly is listed along with its own dimensions and requirements. This allows for more accurate costing and production estimates. It also facilitates the use of process improvement techniques that may uncover new methods or materials for manufacturing.
Types of BOMs
There is no one-size-fits-all when it comes to BOMs. They can be structured based on the product design stage (engineering bill of materials), as they are being ordered by customers for assembly into sales orders (sales BOM), as they are built in a manufacturing process (manufacturing bill of materials, or mBOM), and even when a service team needs to access them to maintain a piece of equipment or machinery (service BOM).
A single-level BOM is a simplistic list where each assembly or sub-assembly that a company makes is shown only once with the associated quantity required. It is a quick and easy BOM to develop but lacks specifics about parent and child parts, or between assemblies and sub-assemblies. This type of BOM is unsuitable for complex products because it can be difficult to identify which part needs to be replaced or repaired in the event that a problem arises.
A configurable BOM, or cBOM, is a BOM which allows companies to dynamically create end-items that they sell to different customers. It is usually driven by configurator software but can also be enabled manually. It reduces the effort that it takes to manage product structures, especially for businesses which deal with a high number of variations in customer orders. It is important for companies to use a cBOM so that the correct version of an item is sent to vendors so that errors don’t occur during production.
Single-level BOMs
A single-level BOM is a simple list with each assembly or subassembly needed for a product displayed once in the top-level of the document. This type of BOM only includes one level of children in components, assemblies and materials and cannot show parent-child relationships. This is a common type of BOM for very simple products, but is not useful when dealing with more complex structures.
Often times, BOMs will contain information about each component like the part number and quantity, as well as some other details about the specific piece like its description or what it’s used for. This information is crucial to making sure that the final product is made correctly. This will also help companies plan budgets and ensure that all the necessary parts are available before starting production, which can reduce delays in delivery to customers.
Additionally, having clear and accurate information about the parts needed will make it easier to manage inventory levels. This can prevent overstocking or shortages and reduce storage costs, as well as ensure that third-party contract manufacturers have the correct parts for the job.
Another important use of a BOM is to track the time it takes to build a particular product. This allows companies to calculate the total lead time and predict how much money will be spent on labor, tools and other materials. This information can also be used to improve productivity and quality by ensuring that each step in the production process is completed on schedule and without errors.
Multilevel BOMs
A multilevel BOM is a type of BOM that contains more than one assembly level. This can be useful for manufacturing companies that produce products with complex production steps. Multilevel BOMs allow you to see the entire production process and manage inventory more effectively. They can also help you avoid overstocking or running out of materials.
To create a multilevel BOM, you will need to identify all of the components in your product and decide how you want to organize them. A good way to do this is by creating a spreadsheet for each assembly level. Each sheet will contain all of the parts needed to construct that assembly level.
Once you have finished creating your spreadsheets, you can begin to link them together using cell references. Once you have linked all of the sheets together, you will have a complete multilevel BOM. You can use this to track the quantity of each component in your product.
A multilevel BOM is an important tool for any manufacturing company. Having a good system in place to manage your BOMs can save you time and money. Fortunately, modern Material Requirements Planning (MRP) systems like Arena Product Lifecycle Management can handle multilevel BOMs easily. These types of systems can automatically calculate totals for each assembly level and can tie the data directly to your shop floor and inventory management.