It is an interesting question - in theory, NO. You should not be able to use a Master Routing for Process Manufacture even if the Bill of Material setup is correctly linked to the correct Op Seq for the Ingredients. You can only setup the Co/By-Products through the Process Routing so I don't know how you would do this if the Route/Process Doesn't exist. Remember that the WO "Part Nbr" is the Process NOT the Co-Product!
If you set it up for the Co-Product then this is Discrete Mfg.... How were you thinking of doing this?
There is a White Paper on setting up Master Routings at my web site if you wish to download it. It is explained in terms of CSMS but the principle is the same. As the Cross Reference File requires two Part Numbers to be related to each other then the Master Routing Item also has to be setup in the Item Master.
