BOM Item Numbering Changes with Change of Model State of Top-Level Assembly or Component

[Jonathan_Schmidt]

There are two related parts to this idea. I have provided a PnG of some dummy models to illustrate. The primary model to open is Main Assembly.iam.

We have base part numbers and we have extensions to those part numbers that represent different variations of that part. Visually, the models of the parts and its variations are the same. The geometry doesn't change at all between these variations. The main model state changes are iProperties like the part number, description, revision, and a few others. Ultimately, these changes appear as BOM changes in a parent assembly. And, the assembly BOMs (including the BOM item numbers) get pushed from Inventor to our ERP system.

Part 1 - BOM Item Numbers Should Be Stored with Each Model State

1. Open Main Assembly.iam.

2. Look at the BOM in the Assembly. (Structured)

3. Note that BOM item numbers are 1, 2, 3 with parts sorted by part number. Close out of BOM.

4. Change Main Assembly's model state from Primary to Variation 1. Note that component Model State Assy 1 also changes to its Variation 1 model state.

5. Re-open the BOM in the Assembly. Note that MSA1's part number is now MSA1-1.

6. Note that the BOM item numbers are 1, 2, 4 and parts are no longer sorted by part number.

7. Sort the BOM by part number and renumber. Close out of BOM.

8. Change Main Assembly's model state back to Primary.

9. Re-open the BOM in the Assembly and note that the parts that were previously sorted are no longer.

The problem with this behavior is that the BOM item numbers get pushed to our ERP system. If the engineer neglects to sort the BOM before pushing it, the item numbers may not be consecutive, and/or the parts may be out of intended order. When the BOM is sorted and numbered (including any static values), those should remain in place for that model state.

Part 2 - Changing a Model State of a Component Changes the BOM Item Number

1. Open Main Assembly.iam and note the BOM (structured) and numbering as before.

2. In the Model State Assy 1 component, change the model state from Primary to Variation 1.

3. Open the Main Assembly's BOM and note that MSA1's part number is now MSA1-1. Also, the parts are again out of order and numbering changed.

Sometimes we decide to swap out a different "variation" of a part in a given assembly. In the model, we would just change the model state to that new variation. But, we do not want the item number of that MSA1 to change when the change is made to that model state. MSA1-1 should remain BOM Item number 2.

Why is this important?

Currently for our documentation/quality process, we have to create one drawing for the base part and one for each variation. On the drawing, the only changes would be in the title block and BOM.

We are trying to set up our processes to have one assembly drawing for just the "base" part number. But, we would like that one drawing to be able to be used for all of the different variations rather than having to create and maintain multiple drawings for essentially the same part/assembly. Because the only changes are to the BOM, it will be much simpler for our documentation to only have to create one drawing and have all the different variations use the same BOM item numbers so that the balloons match that base drawing. If the BOM numbering for Variation 1 is different from the base part drawing, the balloons on the base part drawing won't match the BOM item numbers for Variation 1, which will cause problems for the factory.

In addition, our desire is to remove the BOM from the drawing altogether. When we do this, the item numbering in the BOM (sent from Inventor to our ERP) matching the balloons becomes even more crucial because that is the only way to determine what parts are being ballooned. So, when we set the item numbers in one model state, we need those numbers to remain the same in the above two scenarios.

True, we can sort and renumber each time we switch between model states in the main assembly or a component. But, if someone forgets to do this, the numbering in our ERP system (from the assembly BOM) won't match the drawing balloons (from the base part drawing). This will lead to errors.

Model State BOM.zip

[kacper.suchomski]

Please read this article:

https://help.autodesk.com/view/INVNTOR/2026/ENU/?guid=INV2026-MODEL-STATES

You may be able to update your expectations.

(I personally haven't made a comparison yet)

Regards!

[Jonathan_Schmidt]

Oh thank you! That looks very promising!