chap013 - mrp and erp

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13-1 MRP and ERP

William J. Stevenson

Operations Management

8th edition

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13-2 MRP and ERP

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13-3 MRP and ERP

Material requirements planning (MRP): Computer-based information system that translates master schedule requirements for end items into time-phased requirements for subassemblies, components, and raw materials.

MRP

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Independent and Dependent Demand Independent Demand

A

B(4) C(2)

D(2) E(1) D(3) F(2)

Dependent Demand

Independent demand is uncertain. Dependent demand is certain.

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13-5 MRP and ERP

Dependent demand: Demand for items that are subassemblies or component parts to be used in production of finished goods.

Once the independent demand is known, the dependent demand can be determined.

Dependant Demand

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13-6 MRP and ERPDependent vs Independent Demand

Time

Time Time

Time

Dem

and

Dem

and

Stable demand“Lumpy” demand

Am

ou

nt

on

han

d

Am

ou

nt

on

han

d

Safety stock

Figure 13.1

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13-7 MRP and ERP

MRP Inputs MRP Processing MRP Outputs

Masterschedule

Bill ofmaterials

Inventoryrecords

MRP computerprograms

Changes

Order releases

Planned-orderschedules

Exception reports

Planning reports

Performance-controlreports

Inventorytransaction

Primaryreports

Secondaryreports

Figure 13.2

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13-8 MRP and ERP

Master Production Schedule Time-phased plan specifying timing and

quantity of production for each end item. Material Requirement Planning Process

Product Structure

Tree

Lead Times

MPR Inputs

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13-9 MRP and ERP

Master Schedule

Master schedule: One of three primary inputs in MRP; states which end items are to be produced, when these are needed, and in what quantities.

Cumulative lead time: The sum of the lead times that sequential phases of a process require, from ordering of parts or raw materials to completion of final assembly.

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13-10 MRP and ERP

Planning Horizon

1 2 3 4 5 6 7 8 9 10

Procurement

Fabrication

Subassembly

Assembly

Figure 13.4

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13-11 MRP and ERP

Bill-of-Materials

Bill of materials (BOM): One of the three primary inputs of MRP; a listing of all of the raw materials, parts, subassemblies, and assemblies needed to produce one unit of a product.

Product structure tree: Visual depiction of the requirements in a bill of materials, where all components are listed by levels.

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13-12 MRP and ERP

Product Structure Tree

Chair

Seat

Legs (2) Crossbar

SideRails (2)

Crossbar

BackSupports (3)

LegAssembly

BackAssembly

Level 0

1

2

3

Figure 13.5

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13-13 MRP and ERP

Inventory Records

One of the three primary inputs in MRP Includes information on the status of each

item by time period Gross requirements Scheduled receipts Amount on hand Lead times Lot sizes And more …

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13-14 MRP and ERP

Assembly Time Chart

1 2 3 4 5 6 7 8 9 10 11

Procurement ofraw material D

Procurement ofraw material F

Procurement ofpart C

Procurement ofpart H

Procurement ofraw material I

Fabricationof part G

Fabricationof part E

Subassembly A

Subassembly B

Final assemblyand inspection

Figure 13.7

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MRP Processing

Gross requirements

Schedule receipts

Projected on hand

Net requirements

Planned-order receipts

Planned-order releases

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MPR Processing Gross requirements

Total expected demand

Scheduled receipts Open orders scheduled to arrive

Planned on hand Expected inventory on hand at the beginning

of each time period

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MPR Processing Net requirements

Actual amount needed in each time period

Planned-order receipts Quantity expected to received at the beginning

of the period

Offset by lead time

Planned-order releases Planned amount to order in each time period

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Updating the System

Regenerative system Updates MRP records periodically

Net-change system Updates MPR records continuously

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MRP Outputs

Planned orders - schedule indicating the amount and timing of future orders.

Order releases - Authorization for the execution of planned orders.

Changes - revisions of due dates or order quantities, or cancellations of orders.

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MRP Secondary Reports

Performance-control reports

Planning reports

Exception reports

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13-21 MRP and ERP

Other Considerations

Safety Stock Lot sizing

Lot-for-lot ordering Economic order quantity Fixed-period ordering

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13-22 MRP and ERP

Food catering service End item => catered food

Dependent demand => ingredients for each recipe, i.e. bill of materials

Hotel renovation Activities and materials “exploded” into

component parts for cost estimation and scheduling

MRP in Services

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Benefits of MRP

Low levels of in-process inventories

Ability to track material requirements

Ability to evaluate capacity requirements

Means of allocating production time

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Requirements of MRP

Computer and necessary software Accurate and up-to-date

Master schedules Bills of materials Inventory records

Integrity of data

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13-25 MRP and ERP

Expanded MRP with emphasis placed on integration Financial planning

Marketing

Engineering

Purchasing

Manufacturing

MRP II

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13-26 MRP and ERP

MarketMarketDemandDemand

ProductionProductionplanplan

Problems?Problems?

Rough-cutRough-cutcapacity planningcapacity planning

YesYes NoNo YesYesNoNo

FinanceFinance

MarketingMarketing

ManufacturingManufacturing

AdjustAdjustproduction planproduction plan

MasterMasterproduction scheduleproduction schedule

MRPMRP

CapacityCapacityplanningplanning

Problems?Problems?RequirementsRequirements

schedulesschedules

Ad

just

mas

ter

sch

edu

leA

dju

st m

aste

r sc

hed

ule

MRP IIFigure 13.14

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Capacity PlanningCapacity requirements planning: The

process of determining short-range capacity requirements.

Load reports: Department or work center reports that compare known and expected future capacity requirements with projected capacity availability.

Time fences: Series of time intervals during which order changes are allowed or restricted.

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Capacity PlanningDevelop a tentativemaster production

schedule

Develop a tentativemaster production

schedule

Use MRP tosimulate material

requirements

Use MRP tosimulate material

requirements

Convert materialrequirements to

resource requirements

Firm up a portionof the MPS

Is shopcapacity

adequate?

Cancapacity be

changed to meetrequirements

Revise tentativemaster production

schedule

Changecapacity

Yes

No

Yes

No

Figure 13.15

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Enterprise resource planning (ERP): Next step in an evolution that began with

MPR and evolved into MRPII Integration of financial, manufacturing, and

human resources on a single computer system.

ERP

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ERP Strategy Considerations

High initial cost High cost to maintain Future upgrades Training