Yesterday, I discussed how openBoM calculates parts quantities in BOMs created for Onshape documents. When you use openBOM with Onshape, you will notice three different BOM types available for you to create depending on your needs.
I this article, I want to talk about these BOM types and explain what the difference between them is and recommend when to use which.
BOM creation basics. In the Onshape integrated openBOM app, BOMs are always created as an app tab. This is how the Onshape integrated app mechanism currently works. You can create an unlimited number of tabs for as many BOMs as you want. When you create a BOM, the data is retrieved from Onshape elements, e.g., Assembly or Part Studio. Once a BOM is created, openBoM keeps track of relationships between Onshape elements and the BOM allowing you to keep them in sync and to propagate changes.
There are three BOM types:
Single Level BOM; and
(1) Part List is a flat list of Parts (no assemblies) extracted from assemblies specifically chosen by the user. openBoM will traverse all subassemblies (including all linked documents) to gather parts and calculate quantities. The result will be a flat list with parts and their quantities; read this blog for more info about how quantities are calculated by openBoM for Onshape.
(2) A Single level BOM is a flat list of components (assemblies and parts) located on the first level from the selected assembly. Quantities will be calculated for both subassemblies and parts.
(3) A Multi-level BOM is a structure combined from multiple single level BOMs created by traversing an Onshape assembly top-down and building a single level BOM for each level. The structure will be created automatically by openBoM. Before a multi-level BOM is created, a dialog window will prompt the user to select what properties they want to see in the the multi-level BOM view. After a multi-level BOM is created, you will be offered a configuration dialog to select what properties will be displayed in the grid and what properties will only appear in prop info panel.
Once a BOM is created, you can not change parameters such as BOM type, assembly, and options (such as Group by name, geometrical properties inclusion, etc.). If for some reason you created a BOM with the wrong configuration, you can always delete it and recreate a new one with the desired parameters.
There’s a 4th option for BOM type selection: “Inventory.” You can read more about it, here.