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8/7/2019 5161_SESSION 3 MASTER PRODUCTION SCHEDULING
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OM II
MASTER SCHEDULING
PROCESS
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AGREGATE PLAN
Match seasonal demand with capacity by
- Inventory
- Employment level , OT
- Outsourcing Minimize cost
Manage demand
Manage capacity ( peak demand, chase
demand, level production , hybrid Implications : Cost, capacity utilization,
Customer satisfaction,
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Short-range plans (Detailed plans)
Machine loading
Job assignments
Intermediate plans (General levels) Employment
Output
Long-range plans Long term capacity
Location / layout
Overview of Planning Levels
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MASTER SCHEDULING
Each product : Planned
- Quantity
- Timing- Delivery
Disaggregation
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DISAGGREGATION
Jan 2000 L
W O B
Jan : 1 L 100 50 1500.5 L 200 100 400
0.2 L 200 300 500
Change of units
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Master Scheduling Process
MasterScheduling
Beginning inventory
Forecast
Customer orders
Inputs Outputs
Projected inventory
Master production schedule
Uncommitted inventory
(Available- to promise)
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Projected OnProjected On--hand Inventoryhand Inventory
64 1 2 3 4 5 6 7 8
Forecast 30 30 30 30 40 40 40 40
Customer Orders(committed) 33 20 10 4 2
Projected on-hand
inventory 31 1 -29
JUNE JULY
Beginning
Inventory
Customer orders are
larger than forecast in
week 1
Forecast is larger than
Customer orders in week 2
Forecast is larger than
Customer orders in week 3
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MPS
64 1 2 3 4 5 6 7 8
Forecast
P j
6
MPS 7 7 7 7
7 79 7
JUNE JULY
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Time Fences in MPSTime Fences in MPS
Period
frozen
(firm or
fixed)
slushy
somewhat
firm
liquid
(open)
1 2 3 4 5 8
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OBJECTIVES
Meet due dates
Minimize lead time (P or D)
Minimize setup time Minimize WIP
Maximize resource utilization
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Priority Rules for Job Sequencing
1. First-come, first-served (FCFS)
2. Shortest operating time (SOT)
3. Earliest due date first (DDate)
4. Slack time remaining (STR) first
5. Slack time remaining per operation
(STR/OP)
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OBJECTIVE FUNCTIONS
Mean flow time
Mean Tardiness
Maximum Tardiness
Total no of tardy obs
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EXAMPLE
P
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SPT
JOB p d C F T
3 2 19 2 2 01 4 6 6 6 0
2 7 9 13 13 4
4 8 17 21 21 4
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DD
JOB p d C F T
1 4 6 4 4 0
2 7 9 11 11 2
4 8 17 19 19 2
3 2 19 21 21 2
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MOORE
JOB p d C F T
1 4 6 4 4 04 8 17 12 12 0
3 2 19 14 14 0
2 7 9 21 21 12
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EXAMPLE FLOW SHOP
JOBS p on m/c 1 p on m/c 2
1 4 7
2 6 3
3 2 3
4 7 7
5 8 6
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EXAMPLE FLOW SHOP
M/c 1 M/c 2 TIME
1
2
JOB 1 3
4
5
6
7
JOB 2 JOB 1 8
9
10
JOB 3 11
12
JOB 2 13
14
15
JOB 4 JOB 3 16
17
18
19
20
21
22
JOB 4 23
JOB 5 24
25
26
27
28
JOB 5 29
30
31
32
33
34
35
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JOHNSONS PROCEDURE
M/c 1 M/c 2 ME M/c 1 M/c 21 JO 32
JO 1 3
5 JO 16
JO 2 JO 1 8
9
10 JO 4 JO 1JO 3 11
12
JO 2 13
14
15
JO 4 JO 3 16
17 JO 4
18 JO 5
19
2021
22
JO 4 23
JO 5 24 JO 5
25 JO 2
26
27
28
JO 5 29 JO 2
30
31
32
33
34
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GENERAL JOB SHOP
JOB d
A B C A B C1 3 3 2 10
2 5 2 13
3 4 4 3 12
4 3 5 2 18
5 5 4 14
6 2 5 5 15
p FOR M/C'S
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INDEPENDENT EPQ
SCHEDULING
Product
no.
Annual
Requirement
R
Sales per
day(250
days a
year) p
Days reqd to
meet
requirement
Inventory
cost
Rs/year/unit
Set up
cost
Rs EPQ
No of
runs/year
Days per
lot
1 9000 36 225 40 0.1 40 2928 3.1 13.0
2 20000 80 500 40 0.2 25 2440 8.2 4.9
3 6000 24 200 30 0.15 50 2132 2.8 10.7
4 12000 48 600 20 0.1 40 3230 3.7 5.45 16000 64 500 32 0.02 50 9578 1.7 19.2
6 15000 60 500 30 0.5 40 1651 9.1 3.3
7 8000 32 1000 8 0.35 30 1190 6.7 1.2
8 9000 36 900 10 0.05 60 4743 1.9 5.3
9 2000 8 125 16 0.55 25 441 4.5 3.5
10 3000 12 200 15 0.2 20 799 3.8 4.0
241 380 4.5 70.4
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SCHEDULING INTERFERENCE
Productno. Days per lot Max Inventory
No of
days to
depletemax inv
1 13.0 2459 68
2 4.9 2049 26 Stock out
3 10.7 1876 78
4 5.4 2972 62 Stock out
5 19.2 8352 1316 3.3 1453 24 Stock out
7 1.2 1152 36 Stock out
8 5.3 4554 126
9 3.5 413 52 Stock out
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COMMON CYCLE SCHEDULING
(4 Cycles/Year )
Produc
no a s per o Max n en or
No o
da s o
dep e e
ax n
1 10 0 1890 53
2 10 0 4200 53
3 7 5 1320 55
4 5 0 2760 58
5 8 0 3488 55
6 7 5 3300 55
7 2 0 1936 61
8 2 5 2160 60
9 4 0 468 59
10 3 8 705 59
O L 60 3
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COMMON CYCLE SCHEDULING
(5 Cycles/Year )
Product
no. Days per lot Max Inventory
No of
days to
deplete
max inv
1 8.0 1512 42
2 8.0 3360 423 6.0 1056 44
4 4.0 2208 46
5 6.4 2790 44
6 6.0 2640 44
7 1.6 1549 48
8 2.0 1728 48
9 3.2 374 4710 3.0 564 47
TOTAL 48.2
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Waiting Lines in Service
Operations Irregular or random demand
Service times vary amongcustomers.
Managers try to strike a balance between
efficiently utilizing resources and keeping
customer waiting.
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WAITING LINE ANALYSIS
How many servers to use
Likelihood a customer will have to wait Average time a customer will wait
Average number of customers waiting
Waiting line space needed
Percentage of time all servers are idle
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Waiting Line Examples
Computer printing obs waiting for printing
Workers waiting to punch a time clock
Customers in line at ATM Trucks are waiting to be unloaded
Patients waiting at a path lab
Airplanes waiting to take off
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TERMINOLOGY
Queue - a waiting line
Channels - number of waiting lines in a
queuing system Service phases number of steps in
service process
Arrival rate (P) - rate at which persons orthings arrive (in arrivals per unit of time)
Service rate (Q) - rate that arrivals are
serviced (in arrivals per unit of time)
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TERMINOLOGY
Queue discipline - rule that determines the
order in which arrivals are serviced
Queue length number of arrivals waitingfor service
Time in system an arrivals waiting time
and service time
Utilization degree to which any part of
the service system is occupied by an
arrival
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Queuing System Structures
Single Phase - Single Channel
Single Phase - Multichannel
SS11
SS11
SS22
SS33
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Queuing System Structures
Multiphase - Single Channel
Multiphase - Multichannel
SS1212SS1111
SS1212SS1111
SS2222
SS2121
SS3232SS3131
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WAITI G LI E STRUCTURES
Single Channel
Multichannel
Single
PhaseMultiphase
One-person
barber shopCar wash
Hospital
admissions
Bank tellers
windows
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QUEUING SYSTEM
VARIABLESP = average arrival rate1/P = average time between arrivals
= average service rate for each server
1/ = average service timen1 = average number of arrivals waiting
nS = average number of arrivals in the system
t1 = average time arrivals wait
tS = average time arrivals are in the system
Pn = probability of exactly n arrivals in thesystem
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Independent and Dependent
DemandIndependent 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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MRP
M R PR
M R
R R MP
R
M
PR R R
M R
PR
R R R
P R
R R
R R P R
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PRODUCT STRUCTURE
HIERARCHY
C O P O E T E E
A
S
R
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PRODUCT STRUCTURE
SSE ED
SSE ED
C
PURC SED
D
SSE ED
E
SSE ED
PURC SED
SSE ED
PURC SED
PRODUCED
PRODUCED
K
PURC SED
PRODUCED
PRODUCED
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PROCESS CHART
PART ( ) PART ( )
PERATI N
C P 1( 3 ) PERATI N 2
PURCHA ED
COMP 2( 1 ) OPERATION 2
PURCHA ED
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OUT PUT
OMPO T
QU T T Q O
U T T T
TOT QU T T
Q
G
G
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