In its most basic form, a Bill of Materials (BOM) is a list of all the parts needed to manufacture a product. Depending on your needs, however, it can also encompass a comprehensive list of each of the components, materials, assemblies, and sub-assemblies needed, along with quantities, procedures, processes, and specifications. In short, a well-structured bill of materials can comprise a blueprint for the building of your product, from start to finish. 

The operating principle of a BOM is that it is a custom document that provides the information you require, in a useful format, when you need it, to guide your manufacturing. The most important point to remember is that, in order to be useful, your BOM should meet your requirements. 

Other Names for a BOM

BOMs are used in many industries producing products with widely varying levels of complexity. This means that organizations often use different names for this important tool. Some of the names for a BOM that are used include:

• • Assembly component list
  • Product structure
  • Production recipe
  • Parts table
  • Product structure tree
  • Trigger list

Advantages of Using a BOM

Lists of different types are used to track various things in many situations, from home to office to industry and beyond. They offer a simple way to remember things, track progress, and plan activities. In the product manufacturing arena, BOMs offer many advantages, depending on their complexity, sophistication, and level of usage in the organization. Some of the benefits that come from building and using a well-thought-out BOM are:

• • Ability to plan timely purchases of materials and components
  • Improvement of cost estimates and budget control 
  • Better material and component inventory tracking and management
  • Timely planning and reaction to announced and unannounced component shortages
  • Improved adherence to schedules
  • Enhanced productivity tracking
  • Waste reduction
  • Aid in identifying failures
  • Avoidance of production errors
  • Improvements of supply chain security
  • Better record maintenance for audits or certifications

Types and Structures of a BOM

Organizations use BOMs in three main ways: 

1. Manufacturing BOMs are usually hierarchical in structure, with the finished product noted at the top and following down through the various levels of manufacturing to a beginning point. In addition to listing all required components and materials, the BOM may also note how the components in a product relate to each other. Manufacturing BOMs are typically used by all the departments and vendors involved in manufacturing the final product.
2. Engineering BOMs cover the components and assemblies designed by the engineering department, and show component structure by individual function, typically through technical drawings.
3. Sales BOMs are commonly used prior to product assembly to manage the components or parts that are needed in order to complete the sale of a product.

You may also hear about Configurable BOMs, used to develop products with multiple options; and Template BOMs, which are used with products that require regular service, tracking subcomponents that have been serviced or replaced. 

What to Include in Your BOM

The short answer is that it is up to you and your individual needs and can depend on things like manufacturing systems used, amount of digitization (CAD) involved, and sophistication of your vendors.

There are some basic elements, however, that should be included in most BOM templates, with custom elements added as needed. The basic elements are:

• • Part names: including name changes over time
  • Part numbers: including changes over time (may also be SKUs)
  • Part description: details of each part for identification
  • Quantity: number of each individual parts needed to produce the final product
  • Inventory levels: the quantity of a particular part on hand at any moment
  • Levels: which split up the BOM into various sections depending on the product makeup
  • Manufacturer’s name: often used in part identification
  • Part phase: indicates where a part is in a product’s lifecycle or version
  • Alternate parts: includes information on part substitutes
  • Priority: allows for identification of critical parts or those with longer lead times
  • Procurement specifications: information on how parts are purchased and if they are standard or custom
  • Comments: allows for inserted notes on part or process changes as the product matures

Additional Custom BOM Tracking Elements

A BOM is a critical tool that will change over time in order to adapt to product versions, maturity, and other factors. As you work through the process of developing a useful BOM for your business, you may want to include other tracking elements, depending on your current or anticipated needs. Some of these elements might include:

• • Component costs: the price per unit for individual components
  • Budget metrics: the internal budget (or contract budget) for a particular part
  • BIN number: for physical location of a part in inventory
  • Alarms or trigger points: specific alarms built-in to indicate when a target has been reached or is close
  • Standards requirements: regulatory or consensus specifications that may need to be met at specific points in the manufacturing process in order to pass certifications
  • Audit flags: identify critical points where process or test metrics may be necessary for post-production audits

Things to Watch Out For (data entry, updates, usage compliance, revisions)

A well structured BOM is a database of information on manufacturing a product that, depending on the product’s complexity, may change on a real time basis. As you structure your BOM, it is tempting to include as many data elements as possible. Keep in mind, however, that as you add complexity, you will have to manage several factors such as:

• • Data entry: the more data points you build-in, the more information will be needed
  • Updates: your product sophistication will dictate the update cycle for your BOM
  • Revisions: the individual elements in a BOM change over time even with relatively simple manufacturing details. It is wise to schedule BOM revisions frequently
  • Usage compliance: like most guidance documents, a BOM tool is of little use unless it is employed on an ongoing basis by all interested departments and individuals

Summary

BOMs are critical tools used throughout industry by manufacturers, vendors, assemblers, and auditors to ensure proper product assembly and ultimate performance. You can use the OnlineComponents.com BOM tool to get component quotes for a project at: onlinecomponents.com/en/bomquotes. If you are a frequent visitor to the projects section of our friends over at CircuitBread.com, you can easily use our BOM tool to search for the parts you’ll need.