You can set a scrap factor in the BoM lines on all components involved in the operation. 

But that is % and I need fixed, regardless of how much is made.

You mean - you have a fixed amount of materials in every production?

I know that on old types of machinery in typography,  independent how many copies have been made - always there was scrapped fixed amount materials (paper & ink).

Every time I run a work order independently of how much I make I always have the same amount of loss, so it is an operation loss, but the routing only accounts for time efficiency and the BOM is %, I dont find anywhere to put this fixed loss......

How about adding a line to the BOM for the fixed amount?  You could even link it to an operation such as Set-up.  You could track set-up time if you wish.