Making Stuff: What a Bill of Materials (BOM) is for.
Since I've been making them lately in preparation for the Cookie Dunker (that's the working name, at least, but maybe I should come up with a code name....) I thought I'd talk a little about what a Bill of Materials (B.O.M. or BOM) is, why they're important, and how they're used.
Basically, the best analogy for a B.O.M. is that it is the complete and total recipe for making a product, all the way from the tiniest little screw, to the last little piece of Scotch tape on the outside of the box. It is important to include everything in the B.O.M., because by Murphy's law, if it's not on the B.O.M., something will inevitably be forgotten or misplaced until it's discovered at the least opportune moment.
So since the B.O.M. can be considered a recipe, let's take just that... a recipe. We'll start with just the ingredients list.
Awkward Engineer's Made Up Cookie BOM
| Item # | Qty | Description |
| 1 | 2 cups | Flour |
| 2 | 1 tsp | Baking Soda |
| 3 | 1/2 cup | Sugar |
| 4 | 2 | Eggs |
| 5 | 4 tbsp | Butter |
If you're wondering what order to mix them in, or what temperature the oven should be at, well... that's a very good question. Turns out that if we want our BOM to be a complete and total recipe for making a product, it better be more than an ingredients list. This brings up another good point. It's useful to distinguish on the BOM between different types of items. The mixing directions and oven setting notes can be used over and over, but the flour and eggs and so on get used up and have to be bought from the store. The number and type of category varies from company to company, but a reasonable starting list is Purchased, Made From, Assembly Procedure, Technical Drawing, Artwork We'll also take this time to add the idea of the indented BOM, that items and assemblies on the BOM can be made from other items and assemblies, in a hierarchical fashion. (With a good BOM system, it's also possible to "roll up" or "flatten" portions of the BOM. For example, if a screw is used at different levels of the assembly, when it comes time to order screws, you'd like to know the total in one place so you can place the order.)
The following BOM reflects the added detail. It's possible to display the BOM in a manner that better reflects the tree structure, but in this case, it just uses hierarchical item numbers.
Awkward Engineer's Made Up Cookie BOM
| Item # | Type | Qty | Description |
| 1 | Made From | 1 batch | Cookie |
| 1.1 | Assembly Procedure | -- | Recipe |
| 1.2 | Purchased | 2 cups | Flour |
| 1.3 | Purchased | 1 tsp | Baking Soda |
| 1.4 | Purchased | 1/2 cup | Sugar |
| 1.5 | Purchased | 2 | Eggs |
| 1.6 | Purchased | 4 tbsp | Butter |
Let's say you don't just make cookies though, you wrap them up in a display bag with a label that you print on your home printer, than pack them in boxes for shipment to stores. For the sake of clarity, we'll drop the Qty column and add the Part # column to make our next point about part numbers.
Awkward Engineer's Made Up Cookie Recipe
| Item # | Part # | Type | Description |
| 1 | 1050 | Made From | Carton o' Cookies |
| 1.1 | 1053 | Assembly Procedure | Packing Directions |
| 1.2 | 1022 | Made From | Package Label |
| 1.2.1 | 2012 | Artwork | Adobe Illustrator File |
| 1.2.2 | 3126 | Purchased | Blank Labels |
| 1.3 | 4568 | Purchased | Twistie Tie |
| 1.4 | 9476 | Purchased | Cardboard Box |
| 1.5 | 6154 | Purchased | Tape |
| 1.6 | 6512 | Purchased | Display Baggie |
| 1.7 | 1153 | Made From | Cookie |
| 1.7.1 | 6897 | Assembly Procedure | Recipe |
| 1.7.2 | 3666 | Purchased | Flour |
| 1.7.3 | 1044 | Purchased | Baking Soda |
| 1.7.4 | 3011 | Purchased | Sugar |
| 1.7.5 | 5560 | Purchased | Eggs |
| 1.7.6 | 7899 | Purchased | Butter |
As you can see, each item has a part number, whether it's a document, an art file, or a purchased item. Take a closer look at Item #1.2, the Package Label. Even though the final product doesn't include items 1.2.1 or 1.2.2, they're still part of the complete and total recipe for making the final product. If you only kept track of what the final product looked like, at some point, you would forget to order the blank labels that the final labels are made of.
And that, is BOMs in a nutshell. More advanced topics include configurations, for managing options packages and variations of a product, version control, for managing changes, and route sheets, for managing more complex "made from" processes. We try to apply these principles to the manufacture of our Panic Button and we use them to plan the development of our Cookie Dunker.
And that is one of the things involved in the process of making stuff.