Priority Planning
Definition
Priority planning is the function of determining what to make and when — setting and maintaining valid due dates and quantities for orders — as distinct from capacity planning, which determines whether the resources exist to do it.
In Practice
In MRP-based systems, priority planning is the sequence of master scheduling and material requirements planning that translates demand into time-phased orders with due dates. Its critical discipline is keeping priorities valid: when a customer order moves or a shortage appears, the system must reschedule open orders so their due dates still reflect real need.
Priority planning and capacity planning work as a pair — a plan with valid priorities but impossible load, or ample capacity but stale due dates, both fail on the shop floor. Expedite lists shrink dramatically when order due dates can be trusted.
Frequently Asked Questions
What is the difference between priority planning and capacity planning?
Priority planning decides what is needed and when — order quantities and due dates driven by demand. Capacity planning decides whether work centers have the hours to meet that plan. MRP performs priority planning; rough-cut capacity planning and CRP test the plan's feasibility.
Why do order priorities become invalid?
Demand shifts after orders are released: a customer reschedules, a forecast changes, scrap creates a shortage, or a supplier slips. If due dates are not maintained, the shop works to stale priorities and expediting takes over. Regular MRP replanning and disciplined rescheduling keep priorities honest.
Related Terms
Critical ratio is a dispatching priority index calculated as time remaining until due date divided by work time remaining; a ratio below 1.0 means the job is behind schedule, and lower ratios get worked first.
Job Shop SchedulingJob shop scheduling is the task of sequencing many different jobs across shared work centers in a job shop, where each job follows its own routing, so that due dates, queue times, and machine utilization stay in balance.
Material Requirements Planning (MRP)Material Requirements Planning (MRP) is a calculation engine that translates a production schedule into time-phased requirements for every component and raw material, using bills of materials, inventory records, and lead times.
SlackSlack is the amount of time an order or activity can be delayed without missing its due date, calculated as time remaining until the due date minus the remaining work and setup time.