Valuation rate for not purchased items in BOM

Hy there,
I started using the manufacturing module, and I run the following problem: for some items in BOM I need valuation rate, I can not make a production order…now, we have a lot of semi-manufactured items, which are components of the finished product, and these semi-manufactured product are still manufactured by us, not purchased, nor sell items, in this case, somebody can explain to me what is the valuation rate of these items? how to proceed?
also, we manufacture from fracture of purchased items like we purchase 10 kg x item, but for a batch of Y we use just 2,3 kg, in this case how we need to set valuation rate, I do not really understand the idea.

@umair can you reply?

@Zsolt_Erdelyi Could you please specify your question?, In my understanding you have two question

  1. You can add valuation rate from item master or stock reconciliation. If you update valuation rate, then after manufacturing you can get exact cost on that manufacturing( or semi-manufacturing ) from stock ledger.

  2. You have to use multi level BOM for semi-manufactured item. you can add float number in raw material quantity in BOM.