Bill of Materials: How to Create an Effective BOM?

If you compare building a product with making a cheese cake, then the bill of materials should be the recipe: You want to know what ingredients you still have at home, and you need to make a list of things that you need to purchase later.

In the case of manufacturing a product, the bill of materials (BOM) acts as the list: it includes the product you need to build, what parts you need to build it, how much each part costs, how many of each part do you need, where you should get them from, in what order you should assemble the parts, and more.

Read What is a bill of materials (BOM) if you’re interested in knowing more about it.

That said, we can well say that without the bill of materials, it’s almost close to impossible that we can build the right product. So what should we do to create make sure that we’re creating an effective bill of materials (BOM)?

What to prepare before creating a bill of materials (BOM)?

Using a bill of materials template can really save you tons of time, so you won’t have to start from scratch. But you have to spend time tailoring the BOM template to make it unique to your project or product. Because without cautious preparation and examination of the content on the bill of materials, your product might not be built in time, with quality, or worse, you might end up having no product at all.

1) Know your product

Ask your team and yourself: what are you building? Be sure to include all the parts needed to build your product in the bill of materials (BOM). So you won’t risk building the wrong, or unqualified product.

2) Know your audience

Knowing who will read the BOM helps you include the correct information.

There are different types of bill of materials (BOM): engineering BOM reflects engineering needs when the product is designed by the engineers; manufacturing BOM focuses on the parts needed to build the product and how they are assembled; sales BOM as the product are ordered, and many more.

So include the right information in the BOMs so you can send them to the right people, who can get the right things done. Be ware that some of the people may not have the chance to talk to you personally, so it’s crucial that your BOM is clear, detailed and precise. Otherwise, you risk losing time and money correcting mistakes in the middle of the product development process.

3) Know your needs

Apart from knowing your product, you still need to know what’s missing on your side that’s required to build the product. For instance, does your company still have inventory of certain components? What parts and how many of them do you need, and where you suggest to get them from? What assemblies needs to be modified and what can be purchased off-the-shelf? What components need to be shipped months beforehand? Keep in mind, the general rule here is, the more detailed, the better.

4) Decide how to organize the information

A bill of materials is hierarchical by nature, with the end product at the top level and the assemblies and sub-assemblies at the bottom. Such a structure helps you organize the information logically, so what’s left for you to do is to decide how many levels do you have for the product,¬†how many sub-assemblies do you include in each level, and what special designations you plan to have.

At this point, it’s also important that you consider what tool to use to create the bill of materials. Microsoft Excel is a choice by many, but as your company grows, you may need to consider switching to a more advanced and complex tool that can satisfy your needs better.

What to include in a bill of materials (BOM)?

As mentioned, there are different types of bill of materials targeted at different audience, so it’s not a done deal that you should include, but there are general content that you should include in the BOM:

1) Suggested items in the bill of materials (BOM)

  • Product name: this can be a part of the BOM, or the header of the BOM;
  • Part name: records of the unique name for each part help you identify them easily;
  • Part number: assign a part number to each component so you can identify them quickly;
  • Description:¬†detailed description helps you tell similar parts apart;
  • Quantity: records of the number of the parts needed to make it easier for purchasing and manufacturing;
  • Unit of measure: identify what measurement will be used to purchase or buy the parts. Be consistent with similar part types, so you won’t risk
  • Procurement type: how each part is purchased, i.e. off-the-shelf (OTS) or made-to-specification (MTS);
  • Unit cost: how much each of the assembly cost;
  • Total cost: total cost of the units;
  • Notes: what need to be added to help your audience to increase the efficiency.

2) Included as necessary in the bill of materials (BOM)

  • BOM level: assign the hierarchy levels to the parts, so anyone can easily understand the BOM structure;
  • Reference designator: the reference designator makes it easier to know where the piece goes on the printed circuit board (PCB), and help with the cross-reference the BOM and PCB layout;
  • Supplier: the preferred supplier or vendor that you suggest go to;
  • Phase: where the parts are in their life cycles, such as production, testing and design.
  • Others: such as alternative parts or manufacturers information

Creating a bill of materials from scratch is definitely time and energy consuming, but there are things you can do to make it easier:

  • Use a template that you can usually get from the manufacturers’ sales department;
  • Limit editing permission unless necessary so you won’t risk accidental changes;
  • Always double-check the information to make sure all is accurate if you don’t want to spend extra time and money fixing problems that could’ve been avoid.

Should you have any question related to the bill of materials, feel free to reach out, we’d be glad to help you.

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