mrp & erp - i
TRANSCRIPT
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Materials Requirements
Planning
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Material Requirements Planning (MRP)
MRP Logic and Product Structure Trees
Time Fences
MRP Example
MRP II and Lot Sizing
OBJECTIVES
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Material Requirements Planning
Defined
Materials requirements planning (MRP) is ameans 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 orproduced
Dependent demand drives MRP
MRP is a software system
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Example of MRP Logic and Product
Structure Tree
B(4)
E(1)D(2)
C(2)
F(2)D(3)
A
Product Structure Tree for Assembly A Lead Times
A 1 day
B 2 days
C 1 day
D 3 days
E 4 days
F 1 day
Total Unit Demand
Day 10 50 A
Day 8 20 B (Spares)
Day 6 15 D (Spares)
Given the product structure tree for A and the lead time anddemand information below, provide a materials requirements
plan that defines the number of units of each component and
when they will be needed
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LT = 1 day
Day: 1 2 3 4 5 6 7 8 9 10
A Required
Order Placement 50
First, the number of units of A are scheduled
backwards to allow for their lead time. So, in thematerials requirement plan below, we have to place
an order for 50 units of A on the 9th day to receive
them on day 10.
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Next, we need to start scheduling the components that make up
A. In the case of component B we need 4 Bs for each A.
Since we need 50 As, that means 200 Bs. And again, we back
the schedule up for the necessary 2 days of lead time.
D a y : 1 2 3 4 5 6 7 8 9 1 0
A R e q u i re d 5 0
O rd e r P la c e m e n t 5 0
B R e q u i re d 2 0 2 0 0
O rd e r P la c e m e n t 2 0 2 0 0
B(4)
E(1)D(2)
C(2)
F(2)D(3)
A
SparesLT = 2
4x50=200
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Day: 1 2 3 4 5 6 7 8 9 10
A Required LT=1 Order Placement 50
B Required 20 200
LT=2 Order Placement 20 200
C Required 100
LT=1 Order Placement 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
LT=1 Order Placement 200
B(4)
E(1)D(2)
C(2)
F(2)D(3)
A
40 + 15 spares
Part D: Day 6
Finally, repeating the process for all components, we have the
final materials requirements plan:
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Master Production Schedule (MPS)
Time-phased plan specifying how many and
when the firm plans to build each end item
Aggregate Plan
(Product Groups)
MPS
(Specific End Items)
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Types of Time Fences
Frozen
No schedule changes allowed within this window
Moderately Firm
Specific changes allowed within product groups aslong as parts are available
Flexible
Significant variation allowed as long as overall
capacity requirements remain at the same levels
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Example of Time Fences
8 15 26
Weeks
FrozenModerately
Firm Flexible
Firm Customer Orders
Forecast and availablecapacity
Capacity
Exhibit 15.5
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From Exhibit 15.6
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The McGraw-Hill Companies, Inc., 2004
Firm orders
from known
customers
Forecasts
of demand
from random
customers
Aggregate
product
plan
Bill of
material
file
Engineering
design
changes
Inventory
record file
Inventory
transactions
Master production
Schedule (MPS)
Primary reportsSecondary reports
Planned order schedule for
inventory and production
control
Exception reports
Planning reports
Reports for performance
control
Material
planning
(MRP
computer
program)
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Bill of Materials (BOM) File
A Complete Product Description
Materials
Parts
Components Production sequence
Modular BOM
Subassemblies Super BOM
Fractional options
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Inventory Records File
Each inventory item carried as a separate file
Status according to time buckets
Pegging
Identify each parent item that created demand
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Primary MRP Reports
Plannedorders to be released at a future time Orderrelease notices to execute the planned
orders
Changes in due dates of open orders due to
rescheduling
Cancellations orsuspensions of open orders due
to cancellation or suspension of orders on the
master production schedule Inventory status data
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Secondary MRP Reports
Planningreports, 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
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Additional MRP Scheduling Terminology
Gross Requirements
Scheduled receipts
Projected available balance
Net requirements
Planned order receipt
Planned order release
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MRP Example
A(2
) B(1
)
D(5)C(2)
X
C(3)
Item On-Hand Lead Time (Weeks)
X 50 2
A 75 3
B 25 1
C 10 2
D 20 2
Requirements include 95 units (80 firm orders and 15 forecast) of X
in week 10
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Closed Loop MRP
Production Planning
Master Production Scheduling
Material Requirements Planning
Capacity Requirements Planning
Realistic?No
Feedback
Execute:
Capacity Plans
Material Plans
Yes
Feedback
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Manufacturing Resource Planning
(MRP II)
Goal: Plan and monitor all resources of a
manufacturing firm (closed loop):
manufacturing
marketing
finance
engineering
Simulate the manufacturing system
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Lot Sizing in MRP Programs
Lot-for-lot (L4L)
Economic order quantity (EOQ)
Least total cost (LTC)
Least unit cost (LUC)
Which one to use?
The one that is least costly!