PERT 06 Material Requirement Planning (MRP)

Transcription

1 PERT 06 Material Requirement Planning (MRP) Model Persediaan yang tergantung permintaan Master Production Schedule Bills of Materials Accurate Inventory records Purchase Orders Outstanding Lead Times for Each Component

2 Requirements for Effective Use of Dependent Demand Inventory Models Effective use of dependent demand inventory models requires that the operations manager know the: master production schedule specifications or bills-of-material inventory availability purchase orders outstanding lead times

3 Demand Characteristics Independent demand Dependent demand 100 x 1 = 100 tabletops 100 tables 100 x 4 = 400 table legs No. of tables Continuous demand No. of tables Discrete demand Week M T W Th F M T W Th F

4 Master Production Schedule Shows items to be produced End item, customer order, module Derived from aggregate plan

5 Master Production Schedule Drives MRP process with a schedule of finished products Quantities represent production not demand Quantities may consist of a combination of customer orders and demand forecasts Quantities represent what needs to be produced, not what can be produced Quantities represent end items that may or may not be finished products

6 Master Production Schedule Shows items to be produced End item, customer order, module Derived from aggregate plan Example Item/Week Oct 3 Oct 10 Oct 17 Oct 24 Drills Saws

7 Master Production Schedule PERIOD MPS ITEM Pencil Case Clipboard Lapboard Lapdesk

8 Inputs to the Production Plan Production Capacity Inventory Procurement Supplier Performance Marketing Customer Demand Aggregate Production Plan Finance Cash Flow Human Resources Manpower Planning Management Return on Investment Capital Engineering Design Completion

9 The Planning Process Production Plan Master Production Schedule Material Requirements Plan Capacity Requirements Plan No Yes Realistic?? Execute Capacity Plans Execute Material Plans

10 Inventory Classifications Inventory Process stage Number & Value Demand Type Other Raw Material WIP Finished Goods A Items B Items C Items Independent Dependent Maintenance Dependent Operating

11 Dependent versus Independent Demand Item Demand Source Material Type Method of Estimating Demand Planning Method Materials With Independent Demand Company Customers Finished Goods Forecast & Booked Customer Orders EOQ & ROP Materials With Dependent Demand Parent Items WIP & Raw Materials Calculated MRP

12 Inputs to the Production Plan Production Capacity Inventory Procurement Supplier Performance Marketing Customer Demand Aggregate Production Plan Finance Cash Flow Human Resources Manpower Planning Management Return on Investment Capital Engineering Design Completion

13 The Planning Process Production Plan Master Production Schedule Material Requirements Plan Capacity Requirements Plan No Yes Realistic?? Execute Capacity Plans Execute Material Plans

14 Typical Focus of the Master Production Schedule Number of end items Make to Order (Process Focus) Assemble to Order or Forecast (Repetitive) Stock to Forecast (Product Focus) Schedule finished product Typical focus of the master production schedule Number of inputs Schedule orders Examples: Print shop Machine shop Fine dining restaurant Schedule modules Motorcycles, autos, TVs, fast-food restaurant Steel, Beer, Bread Light bulbs, Paper

15 Bill-of-Material List of components & quantities needed to make product Provides product structure (tree) Parents: Items above given level Children: Items below given level Shows low-level coding Lowest level in structure item occurs Top level is 0; next level is 1 etc.

16 Figure from Example 1

17 Special Bills-of-Material Modular bills Modules are final components used to make assemble-to-stock end items Planning bills Used to assign artificial parent Reduces number of items scheduled Phantom bills Used for subassemblies that exist temporarily

18 Bill-of-Material Product Structure Tree Bicycle(1) P/N 1000 Handle Bars (1) P/N 1001 Frame Assembly (1) P/N 1002 Wheels (2) P/N 1003 Frame (1) P/N 1004

19 Time-Phased Product Structure Start production of D 2 weeks 1 week G D 2 weeks 1 week Must have D and E completed here so production can begin on B 3 weeks D E 2 weeks 2 weeks to produce E 1 week F B A 1 week C

20 Material Requirements Planning (MRP) Manufacturing computer information system Determines quantity & timing of dependent demand items Gross Requirements Scheduled Receipts 5 30 Available Net Requirements 7 Planned Order Receipts 7 Planned Order Releases Corel Corp.

21 MRP Requirements Computer system Mainly discrete products Accurate bill-of-material Accurate inventory status 99% inventory accuracy Stable lead times T/Maker Co.

22 Material Requirements, Planning (MRP) Computerized inventory control and production planning system When to use MRP? Dependent demand items Discrete demand items Complex products Job shop production Assemble-to-order environments

23 MRP Benefits Increased customer satisfaction due to meeting delivery schedules Faster response to market changes Improved labor & equipment utilization Better inventory planning & scheduling Reduced inventory levels without reduced customer service

24 Material Requirements Planning Master production schedule Product structure file Material requirements planning Item master file Planned order releases Work orders Purchase orders Rescheduling notices

25 Structure of the MRP System BOM (Bill-of-Material) Master Production Schedule MRP by period report Lead Times (Item Master File) Inventory Data MRP Programs MRP by date report Planned orders report Purchase requirements Purchasing data Exception reports

26 Table 14.3

27 Derivation of Master Schedule A S B C Lead time = 4 for A Master schedule for A B C Lead time = 6 for S Master schedule for S Master schedule for S sold directly Periods Periods Gross requirements: B = = 45 Therefore, these are the gross requirements for B

28 MRP Systems - Input and Output Bill of Materials Item Master Master Production Schedule Material Requirements Planning System Planned Order & Other Reports Inventory Status Purchasing Data

29 Lot-Sizing Techniques Lot-for-lot Economic Order Quantity Part Period Balancing Wagner-Whitin Algorithm

30 Figure from Example 4

31 Figure from Example 5

32 Figure from Example 6

33 Extensions of MRP Closed loop MRP Capacity planning - load reports MRP II - Material Resource Planning Enterprise Resource Planning

34 Figure 14.8: Closed-Loop MR

35 Extensions of MRP Capacity Planning Tactics for smoothing the load and minimizing the impact of changed lead time include: Overlapping - reduces the lead time, entails sending pieces to the second operation before the entire lot has completed the first operation Operations splitting - sends the lot to two different machines for the same operation Lot splitting - breaking up the order and running part of it ahead of the schedule

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