You should separate the materials you purchase from supplier directly and the materials you assemble. Also you should consider the lead time when will the semi-product could be received when the higher level need it
How to build the workcenter profile is very important. Sometimes, one workcenter can do more than one task in the whole manufacturing cycle.
Routing should be a configuration file and could be modified dynamically.
In order to get the right resource materials at the right time and decrease inventory, usually we will do forecaset first. There are two ways: forward forecast and backword forecast. Also the manager should have the right to change the fence time.
