【正文】 rights reserved. 13 What is MRP? ?Computerized Inventory Control ?Production Planning System ?Management Information System ?Manufacturing Control System Copyright 169。2023 Qi Chao. All rights reserved. 11 Types of Demand ? Independent demand items are those items that we sell to customers. ? Dependent demand items are those items whose demand is determined by other items. Demand for a car translates into demand for four tires, one engine, one transmission, and so on. The items used in the production of that car (the independent demand item) are the dependent demand items. ? Supplies are items such as copier paper, cleaning materials, and pens that are not used directly in the production of independent demand items Copyright 169。2023 Qi Chao. All rights reserved. 9 Economic order quantity ? ?qu antity )ord er(econ omic2con ditio nord erfirst02)(2hADADhddY??????Material Requirements Planning (MRP) Copyright 169。2023 Qi Chao. All rights reserved. 7 The model ? average inventory level: ? The holding cost per unit: ? The setup cost per unit: ? The production cost per unit: 2Q?DhQDhQ22 ???QA?c?Copyright 169。 this is the decision variable Copyright 169。2023 Qi Chao. All rights reserved. 4 The Economic Order Quantity (EOQ) Model ? Assumptions: ? 1. Production is instantaneous. There is no capacity constraint and the entire lot is produced simultaneously. ? 2. Delivery is immediate. There is no time lag between production and availability to satisfy demand. ? 3. Demand is deterministic. There is no uncertainty about the quantity or timing of demand. ? 4. Demand is constant over time. In fact, it can be represented as a straight line, so that if annual demand is 365 units this translates into a daily demand of one unit. ? 5 A production run incurs a constant setup cost. Regardless of the size of the lot or the status of the factory, the setup cost is the same. ? 6. Products can be analyzed singly. Copyright 169。2023 Qi Chao. All rights reserved. 2 Contents for Production Planning and Scheduling Aggregate and Workforce Planning MRP JIT Operations scheduling Project scheduling Aggregate Planning Production Planning and Control Scheduling Review on Economic Order Quantity (EOQ) Model Copyright 169。Copyright 169。2023 Qi Chao. All rights reserved. Material Requirements Planning (MRP) 祁 超 . Associate Professor Institute of Systems Engineering Department of Control Science Engineering Huazhong University of Science Technology Mobile: 13297973735 Copyright 169。2023 Qi Chao. All rights reserved. 3 Copyright 169。2023 Qi Chao. All rights reserved. 5 Notation ? D = Demand rate (in units per year). ? c = Unit production cost, not counting setup or inventory costs (in dollars per unit). ? A = Constant setup (ordering) cost to produce (purchase) a lot (in dollars). ? h = Holding cost ? Q = Lot size (in units)。2023 Qi Chao. All rights reserved. 6 The model Inventory versus time in the EOQ model Copyright 169。2023 Qi Chao. All rights reserved. 8 Economic order quantity ? ?con ditio n)orde r(secon d2)(con ditio norde rfirst02)()un itpercost (total2)(3222QAdYdQADhddYcQADhY???????Copyright 169。2023 Qi Chao. All rights reserved. 10 Copyright 169。2023 Qi Chao. All rights reserved. 12 Why MRP? ? Dependent demand is different from independent demand. Production to meet dependent demand should be scheduled so as to explicitly recognize its linkage to production to meet independent demand. ? Statistical reorder point systems miss the link between independent and dependent demand. ? Buyers are not synchronized with producers. Copyright 169。2023 Qi Chao. All rights reserved. 14 When to use MRP ? Job Shop Production ? Complex Products ? Push Environments ? Discrete and Dependent Demand Items Copyright 169。2023 Qi Chao. All rights reserved. 16 What can MRP do? ? Improve Communication ? Improve Plant Efficiency ? Reduce Freight Cost ? Reduction in Excess Inventory ? Reduce Overtime ? Improve Supply Schedules ? Improve Calculation of Material Requirements ? Improve Competitive Position Copyright 169。2023 Qi Chao. All rights reserved. 18 Quantities timing ? MRP determines appropriate production quantities of all types of items, from final products that are sold, to ponents used to build final products, to inputs purchases as raw materials. ? It must also determine production timing (., job start time) that facilitates meeting order due dates. Copyright 169。2023 Qi Chao. All rights reserved. 20 BOM ?MRP works with both finished products, or end items, and their constituent parts, called lowerlevel items. ?The relationship between end items and lowerlevel items is described by the bill of material (BOM). ?Demand for end items generates dependent demand for lowerlevel items. Copyright 169。 100 LLC=?。2023 Qi Chao. All rights reserved. 22 BOM processor ?Most mercial MRP packages include a BOM processor that is used to maintain the bills of material and automatically assign lowlevel codes. Other functions of the BOM processor include generating “goesinto” lists (where parts are used) and BOM printing. Copyright 169。2023 Qi Chao. All rights reserved. 24 MRP Inputs ?The basic inputs of MRP are a forecast of demand for end items, the associated bills of material, and the current inventory status, plus any data needed to specify production policies. ?These data e from three sources ? The item master file ? The master production schedule ? The inventory status file Copyright 169。 shows quantity and timing of specific end items for a scheduled horizon