The Manufacturer part no F1 help calls for:
Identifies materials of this material type as manufacturer parts.

To allow you to distinguish between manufacturer part numbers in Purchasing, you can create a material master record for each manufacturer part number and assign it to your company's own material.

Note
Only a restricted amount of material master data can be maintained for manufacturer parts. Plant-specific data cannot be maintained in particular.

In real time application - How to do , is there any settings?

Answer:

First Understand the Process of Manufacturer Part Profile :

Create External No ranges for Vendor Account Group MNFR and save.

Now Create Each Make / Manufacturer like ABB as one Vendor in XK01 Trxn code.

Create Material Code original say XXXX in MM01 with ROH material type. (for eg Transistor which is available with ABB & Siemens make)

Create material code for ABB make say 11 with Material type HERS which contain only two views (Basic Data & Purchasing) and give Make, Original material No & Material group and other details and save.

Create material code for Siemens make say 12 with Material type HERS which contain only two views (Basic Data & Purchasing) and give Make, Original material No & Material group and other details and save.

Create a Purchase order with original Material XXXX, then it will ask for mnfg part profile then select the material and click F4 on it, it will show you the created mfg part nos like ABB 11 & Siemens 12 and select one and save.

Prerequisite is you have to Activate Mfg part profile in OMPN trxn code

And in Material master Purchasing View Select the mfg part profile and save

Even if you set the Mfg part number in Display mode in SPRO settings system will throw the same error.

Now What can be done is :

Either go to ME21N and Select material tab after inputting and press f4 and select Manufacturer part number options then system will shows the list of mfg part number maintained to that material select the desired and save.

Else go to MM02 Purchasing View and in Mfg part Profile tab there must be a four character profile assigned to field Remove this and save.

The Second option is not a good practice.

Notes:

Activate the MPN in OMT0.
In OMT3B, select 21 screen seq, and click on data screen, select purchasing and click on subscreen, and replace the screen no 0001 with 2313, then you will get the same in purchasing view for all material types.

REAL TIME SCENERIO: When the parts are manufactured at a plant and procured at that time, in case if any defective piece is there or any problem arises, at that time, the vendor confirms the rejection for the Manufacture part number, so it is entered in the MMR.

You can see the settings here also: SPRO --> MM --> Purchasing --> MM --> Define manufg,. part profiles, this is used to define the profiles.

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