When you set up Microsoft Dynamics NAV production Bill of Material (BOM) lines, you have a choice to select Item or Production BOM.
What is the difference between selecting Item vs Production BOM?
When you select Production BOM, NAV calls it a “phantom BOM” which represents a group of items that are assembled immediately before use in production. The time that is required for assembling a phantom BOM is considered to be zero. Normally phantom BOM is used for non-stocked subassemblies (Figure 1).
Here is an example (Figure 2):
- Finished item number PRODUCT has a Production BOM “PRODUCT” which has Assembly item number PROD1 and PROD2.
- Assembly item number PROD1 has a production BOM “PROD1” which has raw material item number PROD1-1 and PROD1-2.
- Assembly item number PROD2 has a production BOM “PROD2” which has raw material item number PROD2-1 and PROD2-2.
If you select Item, you will find Assembly item PROD1 and PROD2 as Components in the production order of finished item PRODUCT (Figure 3).
NAV will produce the finished item and consume assembly item PROD1 plus PROD2. On Item Ledger Entries, you will find Output Entries and Consumption Entries for assembly item PROD1 and PROD2. (Figure 4)
If you select Production BOM as Type on production BOM Lines, NAV calls PROD1 and PROD2 as phantom BOM. You will not find Assembly item PROD1 and PROD2 as Components in the production order of the finished item; instead, you will find raw material items such as Components in the production order of the finished item (Figure 5).
NAV will produce the finished item and consume the raw material items (note: NAV will not produce and consume any assembly items.) On Item Ledger Entries, you will not find any entries for assembly item PROD1 and PROD2 (Figure 6).
A benefit of handling phantom BOM is that it is not necessary to create an item in NAV; a BOM can be a standalone. It is not necessary to associate it with any item.
In conclusion, deciding whether a subassembly should be set up as a phantom BOM or as an Item is a matter of opinion. Typically engineers or production managers make this decision.
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