What Are The Three Types Of BOM?

different types of bill of materials bom

Whichever industry you work in, you may well have come across the acronym ‘BOM’. This stands for ‘Bill of Materials’ – a list that details the raw materials, sub-components, sub-assemblies, intermediate assemblies, parts, processes, and amounts of each that go into making a finished product. 

Essentially, a bill of materials acts as a formula or assembly instructions for a product or service. But that’s not the end of the story. There are actually various different types of BOM, and the specific sort will depend on which part of the manufacturing process it appears in. 

This post will explain what the three types of BOM are and at which stage of the process you’re most likely to find them. 

1. Manufacturing Bill Of Materials 

As you’d expect, this type of BOM is the most common variety found in the manufacturing industry. A manufacturing bill of materials, otherwise known as a MBOM, is a document that’s used to outline the parts, processes, and assemblies that go into a finished product. This will cover every aspect of the creation process, including any processing that’s required to prepare the raw materials. 

The MBOM will act as a single source of truth that can be shared with the different integrated parts of the business, from the systems which are responsible for sourcing the materials to those which actually build the products. Typically, this includes the enterprise resource planning systems (ERP) and sometimes the manufacturing execution system (MES). 

2. Engineering Bill Of Materials 

An engineering bill of materials (EBOM) functions similarly to a MBOM. Both list the components needed to create a finished product, but one key difference is that EBOMs are generally based on computerised designs during the product design phase. These can include Computer Aided Design tools (CAD) or Electronic Design Automation (EDA). 

In its final form, an EBOM will take the form of a technical drawing of the product. It’s not unusual for engineers to draft various EBOMs throughout the design process, whereas manufacturing bills of materials are usually only drawn up once the raw materials that will be required for the product have been finalised. 2 EBOMs can also just focus on one specific part of the finished product, such as a circuit board or individual structure. 

3. Sales Bill Of Materials 

The Sales Bill of Materials is used to represent the product immediately before it’s assembled, and will appear in the final sales documents. At this stage, the product is treated as a ‘parent item’ – a finished product that’s made up of different components, now known as ‘children’ items. Although the children components are listed as inventory items, the parent item will now be listed as a sales item, because it’s ready to sell. 

For example, an assembled laptop would be listed as a parent item, while the components inside it – such as the motor, microphone, speaker, and circuit boards – would be classed as children items. 

As mass manufacturing and the growing influence of the Internet of Things (IoT) makes product design more complex than ever, BOMs enable businesses to keep track of the process from one end to the other.

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