A multi-level BOM is a BOM which has a top level and one or more sub-levels generally representing a product structure. For example, a bicycle may have a top-level assembly (the bicycle) with several sub-level assemblies such as wheel or handlebar assemblies.  As you can imagine, there may be several “levels” to a products complete Bill of Material.

With that in mind, consider that OpenBOM automatically creates relationships between BOM levels based on unique key property in every BOM – Part Number. In some cases the unique key may be renamed by the integration using an alias; Examples are Onshape where Part number is shown as “Name” and Solidworks where Part number is often represented as “File Name”. Some experimentation on your part will help make this clear.  For now, simply go with the out-of-the-box behavior.

There are three ways to create a multi-level BOM: Generate multi-level BOM directly from CAD structure via the CAD plug-in or integration; Manually (using the Create BOM function) key in BOM items and the various BOM levels using Part Numbers; Restructure single level BOM into multi-level BOM using the BOM restructure commands.

1- Generate multi-level BOM using CAD plug-in or CAD integration

Each OpenBOM plug-in and integration has an option to select what BOM type will be created. One of them is multi-level BOM. Choose that option to get multi-level BOM generated.

Here are few examples:

Onshape:

Solidworks:

2- Manually connect BOM levels using Part Numbers

Check the following screenshot. It shows two BOMs. On the left, you can see top level BOM (DEMO-Wireless Router-D3). On the right you can see sub-level BOM with Part Number (DEMO-Router Top-D3). By manually editing part numbers you can connect any structures of product information in OpenBOM into multi-level hierarchical structures.

3- Restructure single-level BOM into multi-level BOM

This is a method available in multi-level BOM mode in OpenBOM. Check the BOM user interface to select the “Multi-Level” BOM type.

After you’re on the multi-level BOM,  you can notice the Restructure toolbar with two options – “Level-up” and “Level-down”. These commands are operating with selected part by taking it one level down and up. As a result, the part can be transferred to a lower level or upper level. If you move the part to the lower level, new sub-level BOM will be created if you don’t have one.