-
7/29/2019 Planeacion de Requerimientos de Los Materiales
1/26
The McGraw -Hill Companies, Inc., 2004
1
Materials Requirements
Planning
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
2/26
The McGraw -Hill Companies, Inc., 2004
2
OBJECTIVES
Material Requirements Planning (MRP)
MRP Logic and Product Structure Trees
Time Fences
MRP Example
MRP II and Lot Sizing
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
3/26
The McGraw -Hill Companies, Inc., 2004
3
Material Requirements Planning
Defined Materials requirements planning (MRP) is a
means for determining the number of parts,components, and materials needed to producea product
MRP provides time scheduling informationspecifying when each of the materials, parts,and components should be ordered orproduced
Dependent demand drives MRP
MRP is a software system
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
4/26The McGraw -Hill Companies, Inc., 2004
4
Example of MRP Logic and Product
Structure TreeGiven theproduct 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 andwhen they will be needed
Given theproduct 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
B(4)
E(1)D(2)
C(2)
F(2)D(3)
A
Product Structure Tree for Assembly A Lead Times
A 1 dayB 2 daysC 1 dayD 3 daysE 4 days
F 1 day
Total Unit DemandDay 10 50 A
Day 8 20 B (Spares)Day 6 15 D (Spares)
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
5/26The McGraw -Hill Companies, Inc., 2004
5
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 on the 9
th
day to receivethem on day 10.
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.
LT = 1 day
Day: 1 2 3 4 5 6 7 8 9 10
A Required 50
Order Placement 50
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
6/26
7
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
7/26
Finally, repeating the process for all components, we have the
final materials requirements plan:
Finally, repeating the process for all components, we have the
final materials requirements plan:
7
Day: 1 2 3 4 5 6 7 8 9 10A Required 50
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 200LT=1 Order Placement 200
B(4)
E(1)D(2)
C(2)
F(2)D(3)
A
40 + 15 spares
Part D: Day 6
The McGraw -Hill Companies, Inc., 2001
8
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
8/26The McGraw -Hill Companies, Inc., 2004
8
Master Production Schedule (MPS)
Time-phased plan specifyinghow many and
when the firm plans to build each end item
Aggregate Plan(Product Groups)
Aggregate Plan(Product Groups)
MPS(Specific End Items)
9
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
9/26The McGraw -Hill Companies, Inc., 2004
9
Types of Time Fences
Frozen
No schedule changes allowed within this window
Moderately Firm
Specific changes allowed within product groups as
long as parts are available
Flexible
Significant variation allowed as long as overall
capacity requirements remain at the same levels
10
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
10/26The McGraw -Hill Companies, Inc., 2004
10
Exhibit 15.5Exhibit 15.5Example of Time Fences
8 15 26
Weeks
Frozen
Moderately
Firm Flexible
Firm Customer Orders
Forecast and available
capacity
Capacity
11
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
11/26The McGraw -Hill Companies, Inc., 2004
11
Material Requirements Planning System
Based on a master production schedule, amaterial requirements planning system:
Creates schedules identifying the specific partsand materials required to produce end items
Determines exact unit numbers needed
Determines the dates when orders for those
materials should be released, based on leadtimes
12
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
12/26
From Exhibit 15.6From Exhibit 15.6
Firm ordersfrom known
customers
Forecastsof demand
from randomcustomers
Aggregateproduct
plan
Bill ofmaterial
file
Engineeringdesign
changes
Inventoryrecord file
Inventorytransactions
Master production
Schedule (MPS)
Primary reportsSecondary reports
Planned order schedule for
inventory and productioncontrol
Exception reportsPlanning reports
Reports for performancecontrol
Material
planning(MRP
computerprogram)
12
The McGraw -Hil l Companies, Inc., 2004
13
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
13/26The McGraw -Hill Companies, Inc., 2004
Bill of Materials (BOM) File
A Complete Product Description Materials
Parts Components
Production sequence Modular BOM
Subassemblies Super BOM
Fractional options
14
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
14/26
The McGraw -Hill Companies, Inc., 2004
Inventory Records File
Each inventory item carried as a separate file
Status according to time buckets
Pegging
Identify each parent item that created demand
15
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
15/26
The McGraw -Hill Companies, Inc., 2004
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
16
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
16/26
The McGraw -Hill Companies, Inc., 2004
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
17
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
17/26
The McGraw -Hill Companies, Inc., 2004
Additional MRP Scheduling Terminology
Gross Requirements
Scheduled receipts
Projected available balance
Net requirements
Planned order receipt
Planned order release
18
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
18/26
The McGraw -Hill Companies, Inc., 2004
MRP Example
A(2) B(1)
D(5)C(2)
X
C(3)
Item On-Hand Lead Time (Weeks)
X 50 2
A 75 3B 25 1
C 10 2
D 20 2
Requirements include 95 units (80 firm orders and 15 forecast) of X
in week 10
Requirements include 95 units (80 firm orders and 15 forecast) of X
in week 10
19
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
19/26
The McGraw -Hill Companies, Inc., 2004
A(2)
X
Day: 1 2 3 4 5 6 7 8 9 10
X Gross requirements 95
LT=2 Scheduled receipts
Proj. avail. balance 50 50 50 50 50 50 50 50 50 50
On- Net requirements 45
hand Planned order receipt 45
50 Planner order release 45
A Gross requirements 90
LT=3 Scheduled receipts
Proj. avail. balance 75 75 75 75 75 75 75 75
On- Net requirements 15hand Planned order receipt 15
75 Planner order release 15
B Gross requirements 45
LT=1 Scheduled receipts
Proj. avail. balance 25 25 25 25 25 25 25 25
On- Net requirements 20hand Planned order receipt 20
25 Planner order release 20
C Gross requirements 45 40
LT=2 Scheduled receipts
Proj. avail. balance 10 10 10 10 10
On- Net requirements 35 40hand Planned order receipt 35 40
10 Planner order release 35 40
D Gross requirements 100
LT=2 Scheduled receipts
Proj. avail. balance 20 20 20 20 20 20 20
On- Net requirements 80
hand Planned order receipt 80
20 Planner order release 80
It takes
2 As foreach X
It takes
2 As foreach X
20
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
20/26
The McGraw -Hill Companies, Inc., 2004
Day: 1 2 3 4 5 6 7 8 9 10
X Gross requirements 95
LT=2 Scheduled receipts
Proj. avail. balance 50 50 50 50 50 50 50 50 50 50
On- Net requirements 45
hand Planned order receipt 45
50 Planner order release 45
A Gross requirements 90
LT=3 Scheduled receipts
Proj. avail. balance 75 75 75 75 75 75 75 75
On- Net requirements 15hand Planned order receipt 15
75 Planner order release 15
B Gross requirements 45
LT=1 Scheduled receipts
Proj. avail. balance 25 25 25 25 25 25 25 25
On- Net requirements 20hand Planned order receipt 20
25 Planner order release 20
C Gross requirements 45 40
LT=2 Scheduled receipts
Proj. avail. balance 10 10 10 10 10
On- Net requirements 35 40hand Planned order receipt 35 40
10 Planner order release 35 40
D Gross requirements 100
LT=2 Scheduled receipts
Proj. avail. balance 20 20 20 20 20 20 20
On- Net requirements 80
hand Planned order receipt 80
20 Planner order release 80
B(1)A(2)
X
It takes
1 B for
each X
It takes
1 B foreach X
21
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
21/26
The McGraw -Hill Companies, Inc., 2004
Day: 1 2 3 4 5 6 7 8 9 10
X Gross requirements 95
LT=2 Scheduled receipts
Proj. avail. balance 50 50 50 50 50 50 50 50 50 50
On- Net requirements 45
hand Planned order receipt 45
50 Planner order release 45
A Gross requirements 90
LT=3 Scheduled receipts
Proj. avail. balance 75 75 75 75 75 75 75 75
On- Net requirements 15hand Planned order receipt 15
75 Planner order release 15
B Gross requirements 45
LT=1 Scheduled receipts
Proj. avail. balance 25 25 25 25 25 25 25 25
On- Net requirements 20hand Planned order receipt 20
25 Planner order release 20
C Gross requirements 45 40
LT=2 Scheduled receipts
Proj. avail. balance 10 10 10 10 10
On- Net requirements 35 40hand Planned order receipt 35 40
10 Planner order release 35 40
D Gross requirements 100
LT=2 Scheduled receipts
Proj. avail. balance 20 20 20 20 20 20 20
On- Net requirements 80
hand Planned order receipt 80
20 Planner order release 80
A(2) B(1)
X
C(3)
It takes 3
Cs foreach A
It takes 3
Cs for
each A
22
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
22/26
The McGraw -Hill Companies, Inc., 2004
A(2) B(1)
C(2)
X
C(3)
Day: 1 2 3 4 5 6 7 8 9 10
X Gross requirements 95
LT=2 Scheduled receipts
Proj. avail. balance 50 50 50 50 50 50 50 50 50 50
On- Net requirements 45
hand Planned order receipt 45
50 Planner order release 45
A Gross requirements 90
LT=3 Scheduled receipts
Proj. avail. balance 75 75 75 75 75 75 75 75
On- Net requirements 15hand Planned order receipt 15
75 Planner order release 15
B Gross requirements 45
LT=1 Scheduled receipts
Proj. avail. balance 25 25 25 25 25 25 25 25
On- Net requirements 20hand Planned order receipt 20
25 Planner order release 20
C Gross requirements 45 40
LT=2 Scheduled receipts
Proj. avail. balance 10 10 10 10 10
On- Net requirements 35 40hand Planned order receipt 35 40
10 Planner order release 35 40
D Gross requirements 100
LT=2 Scheduled receipts
Proj. avail. balance 20 20 20 20 20 20 20
On- Net requirements 80
hand Planned order receipt 80
20 Planner order release 80
It takes 2
Cs foreach B
It takes 2
Cs for
each B
23
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
23/26
The McGraw -Hill Companies, Inc., 2004
A(2) B(1)
D(5)C(2)
X
C(3)
Day: 1 2 3 4 5 6 7 8 9 10
X Gross requirements 95
LT=2 Scheduled receipts
Proj. avail. balance 50 50 50 50 50 50 50 50 50 50
On- Net requirements 45
hand Planned order receipt 45
50 Planner order release 45
A Gross requirements 90
LT=3 Scheduled receipts
Proj. avail. balance 75 75 75 75 75 75 75 75
On- Net requirements 15hand Planned order receipt 15
75 Planner order release 15
B Gross requirements 45
LT=1 Scheduled receipts
Proj. avail. balance 25 25 25 25 25 25 25 25
On- Net requirements 20hand Planned order receipt 20
25 Planner order release 20
C Gross requirements 45 40
LT=2 Scheduled receipts
Proj. avail. balance 10 10 10 10 10
On- Net requirements 35 40hand Planned order receipt 35 40
10 Planner order release 35 40
D Gross requirements 100
LT=2 Scheduled receipts
Proj. avail. balance 20 20 20 20 20 20 20
On- Net requirements 80
hand Planned order receipt 80
20 Planner order release 80
It takes 5
Ds foreach B
It takes 5
Ds for
each B
24
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
24/26
The McGraw -Hill Companies, Inc., 2004
Closed Loop MRP
Production PlanningMaster Production SchedulingMaterial Requirements PlanningCapacity Requirements Planning
Realistic?No
Feedback
Execute:Capacity PlansMaterial Plans
Yes
Feedback
25
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
25/26
The McGraw -Hill Companies, Inc., 2004
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
26
-
7/29/2019 Planeacion de Requerimientos de Los Materiales
26/26
The McGraw -Hill Companies, Inc., 2004
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!