The production outsourcing module allows to outsource production order per routing. When such outsourced production is set to waiting, a purchase order is created and its cost is added to the production.
To define an outsourced production, the routing must have a Supplier, a Service and its Quantity defined. Those values will be used to create the purchase order. The bought quantity is computed by multiplying the Quantity by the factor between the bill of material and the production quantity.