You must have observed that if your input products have their Identified Stock Type value as Mandatory Specified Stock or Optional Specified Stock, the product specification assigned to your output product will automatically get assigned to them in production orders and production tasks. This behavior of the system is as designed. However, many customers has approached SAP asking that they would want to have their input products consume a product specification other that what the output product is assigned to and they do not want to change the Identified Stock Type of their Input Products also. I have explained below how you can achieve the same.
There exists a Production Model which is released for Planning and Execution for your output product.
The Output Product and Input Product has Identified Stock Type value as Mandatory Specified Stock or Optional Specified Stock.
Identified stock assigned with a product specification exists for the output product.
Identified stock assigned with a product specification exists for the input product as below.
Create a Production Proposal for your output product. This can be done via executing MRP against an existing demand for the product with PRS or manually via the New Planning ProposalCommon Task available under the Supply Planning work center. I am creating the proposal manually.
Enter the Product Id, Planning Area Id, Product Specification ID and Quantity. You can directly Release the Proposal to Production Request as displayed below.
The Production Request will be available in Production Requests view under the Production Control work center.
Select the Proposal and choose the option Full Quantity or Partial Quantity from the Create Order button. I will select Full Quantity option for our scenario.
The system will create a production order with In Preparation status. Please make sure that you do not have automatic production order release configured. If the production order is released you will not be able to perform the work around.
Select the production order from the Production Order view and choose the Edit button.
In the Edit screen navigate to the Product tab and select the sub-tab Input Product. You can see that the product specification of your output product is assigned to the input product as well.
To change this assignment you will have to manually "Key In" or "copy-paste" the identified stock Id of your input product to which the product specification of the input product is assigned. You can see that the system will assign the new product specification to your input products.
You can repeat the same steps to all the input products if required. Save and Release the production order after the above steps. The system will create relevant Production tasks depending upon your production model and Bill of Operation settings. In this scenario we will have only one Make task created.
You can see that the same information is propagated to the make task without errors and the task can be confirmed successfully and the status updated to Finished.
If there are any questions related to the above scenario please update here in the comments so that I can clarify your queries.