Internal PO without Invoice

Question

Our scenario to create a PR to PO for a material that is manufactured in-house.  The PR/PO material is of material type ERSA.  This PO is then sent to our internal sales team who generates a Sales Order.  The Sales Order material is a different material of material type FERT.  The material is then produced in-house and delivered to the appropriate location.  The SD team can configure the Sales document to not include billing. 
Our requirement from an MM side is to determine if it is possible to use some type of Internal PO and to do the GR with the accounting entries generated but not require an invoice.  I realize we can block the invoice from being created but we don't want the invoice to be pending at all.

Answer 1

Hi Jurgen,
The Internal Manufacturing is at the same plant.
Maybe some further explanation will help understand how we arrived at using the PR/PO process. We have recently implemented SAP after transitioning from a home built system that was used for nearly 30 years.  Due to the major complexities during transition we utilized a similar process to which was used in our previous system for internal consumption of material.
Our company manufactures steel and one of our departments called Shops uses this steel to manufacture many things for use around the plant.  Shops currently stocks these plates as ERSA materials controlled through MRP based on the amount of weight of the material left in stock.  When the quantity falls below a certain point the MRP triggers a planned order which is converted into a PR and PO sent to our sales team.  The ERSA material has a short and long description of exactly what size and type of material is required.
The sales team then creates the SO based on the information in the descriptions on the PO and the material entered onto the SO is a FERT material.  This material is specified through many characteristics using Variant Configuration such as Guage, Length, etc.  All of the values in these characteristics are utilized during the production cycle to produce the steel. 
Given this I can't think of how to avoid the use of a PO where a person is converting the material specs into the VC on the SO.  Is there some way we can utilize the FERT material through an MRP run while capturing all of these VC inputs automatically?  How would the production order capture or know this information?  Since there is a single FERT material called "Plate" that can be configured in many different ways to essentially produce a completely different variation of the material how can this be automated based on the Shops departments needs?