Glossary · approach
Material Requirements Planning
The time-phased, dependent-demand planning algorithm that computes, from end-item demand backwards via BOM and lead times, when and how much of every raw material and sub-component is needed.
MRPMaterial Requirements PlanningDependent-Demand Planning
MRP (Material Requirements Planning) is the **time-phased, dependent-demand planning algorithm** named and given its foundational framework by Orlicky (1975). Input: a Master Production Schedule (end-item demand by period), a Bill of Materials (parent-component hierarchy + quantities) and per-part lead times. Output: per part × per period, gross requirements, net requirements (after subtracting on-hand + scheduled receipts and adding safety stock), planned-order receipts (after the lot-sizing rule) and planned-order releases (shifted backwards by the lead time). The core algorithm processes parts level-by-level with low-level coding and explodes the BOM recursively. It is the core algorithm underneath every ERP / manufacturing management system; it extends with pegging (traceback), exception management, frozen horizon and MRP-II capacity validation (Wight 1984). It is on a different layer from classical single-product, independent-demand lot sizing (EOQ, Wagner-Whitin). Sources: Orlicky (1975), Vollmann et al. (2005), Hopp and Spearman (2008).
Örnek
An automotive Tier-2 supplier with 100 end items: a customer orders 500 of product X for delivery in week March-1. MRP explodes the BOM (X = 2A + 3B; A = 4C + 1D), shifts backwards with lead times — in week February-2, a 1,000-unit internal work order for A, a 1,500-unit supplier PO for B; in week January-3, a 4,000-unit PO for C. The whole plan is produced in seconds; with correct parameters (current lead times, frozen horizon, calibrated lot sizing), inventory drops 15-30% and on-time delivery rises 10-20%.