Post on 02-Jan-2016
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DELIVERABLES OF DESIGN REVIEW 1
Statement of problem/need
Customer needs
Product Design Specifications (PDS)
Design targets
Project plan
TOOLS USED TO PRODUCE THOSE DELIVERABLES
Customers research
QFD
Gantt’s chart
CPM (if applicable)
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PLANNING THE DESIGN PROJECT IN MME259a
Design review 1
Design review 2
Design review 3
Final report
Gantt’s chart should be updated by actual project progress (here in red)
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CRITICAL PATH METHOD (CPM)
Complex projects tasks require a series of activities, some of which must be
performed sequentially and other can be performed in parallel with other activities.
The collection of series and parallel tasks can be modeled as a network.
The Critical Path Method (CPM) was developed in 1957 as a network model for
project managements. CPS is a deterministic method using a fixed time estimate for
each activity.
The Critical Path Method - is a project planning technique used to determine the most
efficient sequence of tasks.
A modification of CPM is PERT (Program Evaluation and Review Technique) which
takes into consideration that tasks duration may vary.
http://hadm.sph.sc.edu/COURSES/J716/CPM/CPM.html
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In a project, an activity is a task that must be performed and an event is a milestone marking the completion of one or more activities. Before an activity can begin, all of its predecessor activities must be completed.
The milestone can be numbered so that the ending node of an activity has a higher number the beginning node. It is convenient to increment the numbers by 10 so that new nodes may be easily inserted.
The activities are labeled with letters along with the expected time required to complete the activity.
MILESTONE
Node 40 (labeled as number)
event marking completion of an
activity
TASK
Activity E (labeled as letter)
Duration 3 weeks
CRITICAL PATH METHOD (CPM)
5
A
3
CRITICAL PATH METHOD (CPM)
Primary elements of a CPM diagram :
Activity - is a time consuming effort that is required to perform part of the project (a task). An activity is represented by an arrow.
Event - is a point of accomplishment and/or decision (i.e. a milestone). It marks the end of one activity and the beginning of another. An event is represented by a circle.
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RULE 2. An event cannot be reached (a task can not be completed) until all activities leading to it are complete.
Activities F and G must both be completed before activity H can begin.
Logic restrictions to constructing CPM diagrams:
RULE 1. An activity cannot be started until its tail event is reached
Activities D and E cannot begin until activity C has been completed.
CD
E
1
HF
G
2
CRITICAL PATH METHOD (CPM)
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Activity A must precede both B and C
– B must precede D and E
– C must precede E
– D and E must precede F
– Note: Dummy activities show a sequential connection but no expenditure of time.
RULE 3. Sometimes an event is dependent on another event preceding it, even though the two events are not linked together by an activity.
0
2
1 3
54
A
D
E
F
B
C
CRITICAL PATH METHOD (CPM)
Logic restrictions to constructing CPM diagrams:
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Example:
The CPM network shown below for constructing a building implies that the window frames can be installed before the walls are built (an illogical situation).
By adding a dummy activity, the network now indicates that the installation of window frames has to await both the fabrication of the window frames and the building of the walls.
0
10
20
30
Build WallsConstruct Roof
Make Window Frames Install Window Frames
0
10
20
30
Build WallsConstruct Roof
Make Window Frames Install Window Frames
20 20
4 2
CRITICAL PATH METHOD (CPM)
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Basic parameters for time estimates :
ES - Earliest Start Time The earliest time that an activity can begin when all preceding activities are completed as rapidly as possible.
LS - Latest Start TimeThe latest time that an activity can be initiated without delaying the minimum completion time for the project.
EF - Earliest Finish Time EF = ES + D where D is the duration of each activity.
LF - Latest Finish Time LF = LS + D
.TF - Total Float Time (slack)TF = LS – ES
Note: An activity on the critical path has zero total float TF = 0
CRITICAL PATH METHOD (CPM)
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ES = 4
node 50:
B, E ES = 6
A, D ES = 5
A, C, F ES = 7
ES = 3
ES = 4
Calculation of early start times ES based on CPM diagram.
ES times are determined by starting at the first event (node) and making a forward pass through the network while adding each activity duration to the ES of the preceding activity.
CRITICAL PATH METHOD (CPM)
ES for the last activity actually means the end of project
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ES = 4
ES = 3
ES = 4
CRITICAL PATH METHOD (CPM)
Calculation of late start LS times based on CPM diagram.
LS times are calculated by starting at the last event (node) and a backward pass is made through the network while subtracting the activity duration from the limiting LS at each event
LS = 5
LS = 3
LS = 4
ES = 7
12
ES = 4
ES = 7ES = 3
ES = 4
CRITICAL PATH METHOD (CPM)
An activity on the critical path has zero total float (slack)
TF = LS – ES = 0
LS = 5
LS = 3
LS = 4
SLACK = 1
SLACK = 0 SLACK = 0
CRITICAL PATH
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Gantt chart for testing a heat exchanger.
Activities for testing a heat exchanger.
Example: Prototype testing of heat exchanger.
CRITICAL PATH METHOD (CPM) – EXAMPLE 1
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STEP 1 Perform forward pass to determine ES for each activity
ES times are determined by starting at the first event (node) and making a forward pass through the network while adding each activity duration in turn to the ES of the preceding activity.
3
13
12
16 18 20
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Example: Prototype testing of heat exchanger.
CRITICAL PATH METHOD (CPM) – EXAMPLE 1
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STEP 2 Perform backward pass to determine LS for each activity
LS times are calculated by starting at the last event (node) and a backward pass is made through the network while subtracting the activity duration from the limiting LS at each event
16
18 – 2 = 16
18
20 – 2 = 18
20
12
16-3=13
13
16 – 3 = 13
Example: Prototype testing of heat exchanger.
713 – 5 = 813 – 6 = 7
3
13 - 3 = 10
7- 4 = 3LIMITING LS
LIMITING LS
I
CRITICAL PATH METHOD (CPM) – EXAMPLE 1
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16
18 – 2 = 16
18
20 – 2 = 18
20
12
16-3=13
13
16 – 3 = 13
Example: Prototype testing of heat exchanger.
713 – 5 = 813 – 6 = 7
3
13 - 3 = 10
7- 4 = 3LIMITING LS
LIMITING LS
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STEP 3 Find critical path
Critical path is where TF = 0
CRITICAL PATH METHOD (CPM) – EXAMPLE 1
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Example: Prototype testing of heat exchanger.
Summary of boundary timetable.
CRITICAL PATH METHOD (CPM) – EXAMPLE 1
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CRITICAL PATH METHOD (CPM)
ES is determined by forward pass through network
LS is determined by backward pass through network
Time float TF = LS – ES
Path where TF = 0 is the CRITICAL PATH
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3
2 2
12
4
1
2
2
10
20
30
40
5060
70 80
CRITICAL PATH METHOD (CPM) – EXAMPLE 2
20
3
2 2
12
4
1
2
2
10
20
30
40
5060
70 80
3
?
5
?
8
?5
?
9
?1
?3
?
5
?
Forward pass to determine ES
7
?
CRITICAL PATH METHOD (CPM) – EXAMPLE 2
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3
2 2
12
4
1
2
2
10
20
30
40
5060
70 80
36 - 2 = 45 - 2 = 3
5
8 – 2 = 6
8
5
9 – 4 = 5
9
9
1
7 – 2 = 5
3
9 – 2 = 7
5
Backward pass to determine LS
7
9 – 1 = 8
CRITICAL PATH METHOD (CPM) – EXAMPLE 2
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3
2 2
12
4
1
2
2
10
20
30
40
5060
70 80
36 - 2 = 45 - 2 = 3
5
8 – 2 = 6
8
5
9 – 4 = 5
1
7 – 2 = 5
3
9 – 2 = 7
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The critical path where we must not allow any delayor else the final event will not be reached in 9 weeks
7
9 – 1 = 8
9
9
CRITICAL PATH METHOD (CPM) – EXAMPLE 2
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Activity Description Time estimate, weeks
Preceded by
A Product design 5 none
B Market research 1 none
C Production analysis 2 A
D Product model 3 A
E Sales brochure 2 A
F Cost analysis 3 C
G Product testing 4 D
H Sales training 2 B, E
I Pricing 1 H
J Project report 3 F, G, I
EX 1.The various activities associated with developing a new product are summarized below.
(i) Draw a CPM network diagram for completing the above activities in the proper sequence
(ii) Determine the critical path by calculating ES, LS, EF, LF and TF
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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1
2
3
5
4 7 8
6
A(5)
B(1)
E(2)
H(2) I(1)
F(3)
C(2)
D(3)
G(4)
J(3)
Productdesign
A5
MarketResearch
B1
ProductionAnalysis
C2
ProductModel
D3
CostAnalysis
F3
Producttesting
G4
Salesbrochure
E2
Salestraining
H2
Pricing
I1
Projectreport
J3
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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1
2
3
5
4 7 8
6
A(5)
B(1)
E(2)
H(2) I(1)
F(3)
C(2)
D(3)
G(4)
J(3)
1512
9
7
7
8
5
0
Forward pass to determine ES
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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1
2
3
5
4 7 8
6
A(5)
B(1)
E(2)
H(2) I(1)
F(3)
C(2)
D(3)
G(4)
J(3)
1515-3=12
12-1=11
11-2=9
12-3=9
12-4=8
8-3=5
1512
9
7
7
5
0
8
Backward pass to determine LS
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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Activity Description D ES LS EF LF TF
A Product design 5 0 0 5 5 0
B Market research 1 0 8 1 9 8
C Production analysis
2 5 7 7 9 2
D Product model 3 5 5 8 8 0
E Sales brochure 2 5 7 7 9 2
F Cost analysis 3 7 9 10 12 2
G Product testing 4 8 8 12 12 0
H Sales training 2 7 9 9 11 2
I Pricing 1 9 11 10 12 2
J Project report 3 12 12 15 15 0
D = Duration (weeks)
ES = Earliest Start
LS = Latest Start
EF = Earliest finish (ES + D)
LF = Latest finish (LS + D)
TF = Total float time (LS-ES)
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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1
2
3
5
4 7 8
6
A(5)
B(1)
E(2)
H(2) I(1)
F(3)
C(2)
D(3)
G(4)
J(3)
Total Project duration = 15 weeks
CRITICAL PATH METHOD (CPM) – EXAMPLE 3
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Activity Description Time estimate, weeks
Preceded by
A Investigation and planning 5 none
B Customer feedback 2 none
C Define the market 1 none
D Initial concept design 4 A
E Concept Selection 3 B
F System modeling 2 B, C, E
G Detail Design 3 B, C, E
H Initial Prototype 3 B
I Testing 3 A, D
J Final Prototype 2 A, D
K Production 1 G, H, I
L Establish product cost 2 F
CRITICAL PATH METHOD (CPM) – EXAMPLE 4
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1
3
4
5
8
7
6
2
CRITICAL PATH METHOD (CPM) – EXAMPLE 4
Investigation
and planning A5
Customer
feedback
B2
Define the market C1
Initial concept
Design D4
Concept SelectionE3
System modelingF2
Detail Design
H3
Detail Design
G3
TestingI3
Final Prototype
J2
ProductionK1
Establish product costL2
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13
4
5
8
7
A(5)
B(2)
E(3)
H(3)
I(3)
F(2)
D(4)
G(3)
J(2)
C(1)
6
2
K(1)
L(2)
13
5
2
5 7
9
12
CRITICAL PATH METHOD (CPM) – EXAMPLE 4
Forward pass to determine ES
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13
4
5
8
7
A(5)
B(2)
E(3)
H(3)
I(3)
F(2)
D(4)
G(3)
J(2)
C(1)
6
2
K(1)
L(2)
13
5
9
9 11
LS=9
12
CRITICAL PATH METHOD (CPM) – EXAMPLE 4
Backward pass to determine LS
13
5
2
5 7
9
12
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Activity Description D ES LS EF LF TF
A Investigation and planning 5 0 0 5 5 0
B Customer feedback 2 0 4 2 6 4
C Define the market 1 0 8 1 9 8
D Initial concept design 4 5 5 9 9 0
E Concept Selection 3 2 6 5 9 4
F System modeling 2 5 9 7 11 4
G Detail Design 3 5 9 8 12 4
H Initial Prototype 3 2 9 5 11 9
I Testing 3 9 9 12 12 0
J Final Prototype 2 9 11 11 13 2
K Production 1 12 12 13 13 0
L Establish product cost 2 7 11 9 13 4
CRITICAL PATH METHOD (CPM) – EXAMPLE 4
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13
4
5
8
7
A(5)
B(2)
E(3)
H(3)
I(3)
F(2)
D(4)
G(3)
J(2)
C(1)
6
2
K(1)
L(2)
Total Project duration = 13 weeks