The stock controller needs to ensure that sufficient raw materials are available for production. This can be done using MRP order in the suppliers module, monitoring stock levels and movement from the Inventory module or monitoring stock requirements from production orders directly, using the "Bill of Materials" or "Stock levels" tabs.
Using MRP orders will allow the stock controller to create purchase orders based on usages or stock levels. For more detail see "Material Resource Planning (MRP Orders)" in this self-help reference.