How to make sure your Bill of Materials is the BOM!
A bill of materials, or BOM, is a detailed list of the basic materials, parts, and components needed to manufacture and assemble your product. It also may contain instructions for purchasing and using these materials. Think of a bill of materials as the recipe and shopping list for making your product.
When working with a manufacturer, having an up-to-date BOM is important to keeping everybody on the same page. There are two kinds of bill of materials: an engineering bill of materials (EBOM) and a manufacturing bill of materials (MBOM).
Engineering bill of materials
An EBOM is structured from the design point of view. Read more about it here.
Manufacturing bill of materials:
An MBOM is the list of all of the parts and components needed to contruct and assemble the final, shippable product. Unlike an EBOM, the MBOM may include packaging and any other materials used in the manufacturing process More on MBOM here.
Single level or multi-level bill of material?
A single layer BOM refers to a bill of materials which is for simpler, straight forward products.
A single layer BOM may be all that your team needs if the components are common or outsourced.
The term multi-level BOM refers to bills of material which include several assemblies or sub-assemblies. Each sub-assembly in a multi-layer BOM links to a separate bill of materials which lists the parts in that sub-assembly.
For example, the BOM for a computer will include a hard drive, power supply, motherboard, etc. Each one of these items are complex systems in themselves and will have their own, separate bill of materials which may be included in a multi-layer bill of materials.
Many multi-layerBOMs are so complex they will need Enterprise Resource Planning (ERP) software to manage them.
The term layer is also a little confusing ’-because when referring to “layers” in a bill of material what is meant is simply the line number. In reality, all BOM’s have multiple layers but not all of them are considered multi-layer.
What a basic bill of materials should include.
- BOM Levels
This is the bill of materials’ numbering list. In an MBOM it is recommended to list the parts in the order they are assembled.
- Part Number
Each part should have an assigned part number. If the part is outsourced, using the suppliers’ part number is optimal and will avoid confusion.
- Part Name
Whatever you want to call it.
- Phase
What stage is this part in? Is it “in design”, “approved”, ”To Be Approved”, “In Production”, Revisions (R1, R2, etc).
- Description
Describe each part in detail to avoid confusion between similar parts.
- Quantity
How many parts are needed in each product.
- Unit of Measure
Each, inches, millimeters, etc.
- Procurement Type
Is the part outsourced or made “in-house. If outsourced, list the supplier or suppliers.
- Notes
Any details your team may need to build the product.
As noted earlier in this article, it’s important to understand who will use the BOM. I also like to include pricing of materials, the units in which they are purchased, the units in which they are used in the assembly and the price per unit in my internal BOM’s.
If the Bill of Materials is being used on the manufacturing floor you probably only need the information that the team on the factory floor will need to see. Only you will know what exactly you need to include in the Bill of Material and which version you need.
Creating a clear and efficient Bill of Materials will keep everybody in the manufacturing process of your product literally, on the right page.
Jason Post
Director of Business Development