Discrete manufacturers of machinery, electrical equipment, engineered components and auto parts build from multi-level bills of material. Parts follow routings through work centers such as machining, fabrication, heat treatment and assembly, and some operations, like plating or heat treatment, go out to subcontractors.
Much of the business is make-to-order. The customer asks for a date when the order is placed, and that date depends on long-lead purchased parts such as castings and forgings and on the most loaded work center. Spares and aftermarket orders run beside the main build plan on a lumpier demand pattern of their own.