Tailieumienphi - VN Lecture Logistics Theory Lecture 16 Material Requirements Planning

Material Requirements Planning
Learning objectives
At the end of this lecture, students should be
able to understand
Material Requirements Planning (MRP)
MRP Logic and Product Structure Trees
MRP Example
Lot Sizing in MRP Programs
 Materials requirements planning (MRP) is the
logic for determining the number of parts,
components, and materials needed to
produce a product.
 MRP provides time scheduling information
specifying when each of the materials, parts,
and components should be ordered or
produced.
 Dependent demand drives MRP.
 MRP is a software system.
Example of MRP Logic and
Product Structure Tree
Given the product structure tree for “A” and the lead time and demand
information below, provide a materials requirements plan that defines
the number of units of each component and when they will be needed.
Lead Times
Product Structure Tree for Assembly A A 1 day
B 2 days
A C 1 day
D 3 days
E 4 days
F 1 day
B(4) C(2)
Demand
Day 10 50 A
D(2) E(1) D(3) F(2) Day 8
Day 6
20 B (Spares)
15 D (Spares)
First, the number of units of “A” are scheduled backwards to
allow for their lead time. So, in the materials requirement plan
below, we have to place an order for 50 units of “A” in the 9th
week to receive them in the 10th week.
Day: 1 2 3 4 5 6 7 8 9 10
A Required 50
Order Placement 50
LT = 1 day
Next, we need to start scheduling the components that make up “A”. In
the case of component “B” we need 4 B’s for each A. Since we need 50
A’s, that means 200 B’s. And again, we back the schedule up for the
necessary 2 days of lead time.
Day: 1 2 3 4 5 6 7 8 9 10
A Required 50
Order Placement 50
B Required 20 200
Order Placement 20 200
LT = 2
Spares
A 4x50=200
B(4) C(2)
D(2) E(1) D(3) F(2)

Finally, repeating the process for all components, we have the 7
final materials requirements plan:
Day: 1 2 3 4 5 6 7 8 9 10
A Required 50
LT=1 Order Placement 50
B Required 20 200
LT=2 Order Placement 20 200
C Required 100
D Required 55 400 300
LT=3 Order Placement 55 400 300
E Required 20 200
LT=4 Order Placement 20 200
F Required 200
A
Part D: Day 6
40 + 15 spares
B(4) C(2)
D(2) E(1) D(3) F(2)

Material Requirements
Planning System
 Based on a master production schedule,
a material requirements planning
system:
 Creates schedules identifying the
specific parts and materials required
to produce end items.
 Determines exact unit numbers
needed.
 Determines the dates when orders for
those materials should be released,
based on lead times.
9
Firm orders Aggregate Forecasts

from known product of demand
customers plan from estimates
Master
Engineering
production Inventory
design
schedule transactions
changes
(MPS)
Bill of Material Inventory

material planning record
file (MRP) file
Reports
Bill of Materials (BOM) File
A Complete Product Description
 Materials
 Parts
 Components
 Production sequence
 Modular BOM
 Component or Subassemblies BOM
 Planning BOM or kits
 create an artificial parent to the BOM used for inexpensive items
like washers or pins to group.
 Explosion: revealing the requirements for each
component.
Coding
 If identical items exist
A
at various levels in the
BOM:
 Item is coded at lowest
level at which it occurs B C
 D (Level 2 or Level 3)
 This number identifies
the part at the lowest
D E E F
level of usage.
G D
Inventory Records File
 Buckets= time units in MRP system
 Week bucket vs. day bucket
 Each inventory item carried as a separate file
 Status according to “time buckets”.
 Pegging
 Identify each parent item that created demand.
 Parent vs. child
 Parent= Items above the current level
 Child = Items below the current level
Primary MRP Reports
 Planned orders to be released at a future time.
 Order release notices to execute the planned
orders.
 Changes in due dates of open orders due to
rescheduling.
 Cancellations or suspensions of open orders
due to cancellation or suspension of orders on the
master production schedule.
 Inventory status data.
Secondary MRP Reports
 Planning reports, for example, forecasting
inventory requirements over a period of
time.
 Performance reports used to determine
agreement between actual and
programmed usage and costs.
 Exception reports used to point out
serious discrepancies, such as late or
overdue orders.
Additional MRP Scheduling
Terminology
 Gross Requirements: needed during each period.
 Scheduled Receipts: Existing orders that arrive at beginning of
period.
 Onhand or available balance:
 (depending on software convention, could be at the beginning of each
period or end):
 Book: Inventory balance at end of each period.
 Net requirements: What is need to meet requirements and safety
stock.
 Planned order receipt: arrives at beginning of period.
 Planned order release: Addresses lead time.
MRP Examples
Closed Loop MRP
Production Planning
Master Production Scheduling
Capacity Requirements Planning
No
Realistic? Feedback
Feedback
Yes
Execute:
Capacity Plans
Material Plans
Lot Sizing in MRP Programs
 Lotforlot (L4L)
 Economic order quantity (EOQ)
 Least total cost (LTC)
 Least unit cost (LUC)
 Part Period Balancingchanging lot sizes to
reflect requirements in the future (how
many periods should be combined to
reduce cost)
MRP Game
Different types of lot sizes
Tinker Toy Lawn Mower

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Material Requirements Planning

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

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

Firm orders Aggregate Forecasts

Bill of Material Inventory

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