There are times when engineers and designers want the Bills of Materials (BOMs) for subassemblies to have specific behavior when shown on the top-level Bill of Materials. 

There may be purchased, manufactured, or serviceable subassemblies that only need to be referenced by their assembly number, without their containing parts, on the BOM.

Additionally, there may be instances in CAD where it is necessary to group parts into phantom assemblies, but show only the components in the BOM.

Manipulating BOM Behavior

This can be achieved in Onshape using the BOM behavior property. To take advantage of this behavior, navigate to the Properties dialog for the assembly by either right-clicking on the tab for the assembly or directly on the actual subassembly in the top-level assembly. 

From here, scroll to the Subassembly BOM behavior field. There are three options:

  1. Show assembly and components: With this option, in a Structured View of the BOM, the assembly is listed along with individual line items for each assembly component. This is the default selection for assemblies.

  2. Show assembly only: With this option, in a Structured View of the BOM, only the assembly is listed (no components). This option is helpful with subassemblies purchased or assembled as a unit and incorporated with the next or top assembly level.

  3. Show components only: In a Structure View of the BOM, only the components are listed (no assembly line item). This option helps keep assemblies organized, facilitates configurations, and allows the reuse of collections of parts.

For many manufacturing operations, it is logical for their shop floor employees to gather all materials for a BOM, build subassemblies, and move all parts to different work locations as needed. 

However, as shown, there are opportunities to give engineers, designers, and product managers some options and organization with the Onshape BOM behavior property.

Learn more by watching the video below:

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