ENG209: ENGINEERING MANAGEMENT (Elective Course for EEE Students) (2016 Fall, Week 11) Prof. Dr. Mete Gündoğan Slides Preparation Res. Asst. Cihat Öztürk (IE PhD Candidate) Res. Asst. Melda K. Akgün (IE MSc Candidate) 1
ENG209 Week_11
SECTION 4 TIME MANAGEMENT Lesson Content: Project Scheduling and Control Techniques Gantt Charts CPM (Critical Path Method) Program Evaluation and Review Technique (PERT)
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ENG209 Week_11
GANTT CHART • Graph or bar chart with a bar for each project activity that shows
passage of time • Provides visual display of project schedule
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ENG209 Week_11
GANTT CHART • Each bar shows the inception time, finish time and duration of an • • • •
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activity. It is preferable because of simplicity and userfriendliness. It doesn’t necessitate qualified employee Every line shows a different workbench, workpiece, product or order. Columns show dates and horizontal size shows time (duration).
ENG209 Week_11
GANTT CHART Advantages It is easy to understand You can follow progress easily Creation is easy It is one of the most preferable methods to tell project to the
customers or managers.
Disadvatages It could be superficial. Seeing precedence relationship could be impossible. 5
ENG209 Week_11
Steps to Creating a Gantt Chart: Determine Project start date and deadline. ii. Gather all information surrounding the list of activities within a project – the Work Breakdown Structure may be useful for this. iii. Determine how long each activity will take iv. Evaluate what activities are dependant on others v. Create Graph shell including the timeline and list of activities. vi. Using either Forward Scheduling or Backward Scheduling, Begin to add bars ensuring to include dependencies and the full duration for each activity. i.
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ENG209 Week_11
Example: Activity
Duration
Dependant On
1. Read Literature 2. Conduct Literature Review 3. Arrange Client Visits 4. Prepare Surveys 5. Conduct Surveys 6. Analyse Surveys 7. Write Up
21 days 14 days 7 days 5 days 14 days 10 days 30 days
N/A 1 N/A 1 and 3 4 5 1,2,3,4,5 and 6
Project Start Date = 1st September Deadline = 20th Decemeber 7
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Example:
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ENG209 Week_11
Activity
Duration
Dependant On
1.read
21 days
N/A
2. Conduct literature
14 days
1
3. arrange
7 days
N/A
4. prepare
5 days
1 and 3
5. Conduct surveys
14 days
4
6. analyse
10 days
5
7. Write up
30 days
1,2,3,4,5 and 6
Gantt Chart - Example
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ENG209 Week_11
CPM (CRITICAL PATH METHOD) • CPM is a network diagramming technique used to predict total
project duration. • CPM is an analysis technique with three main purposes: To calculate the project’s finish date To indentify to what extent each activity in the schedule can slip(float) without delaying the project To identify the activities with highest risk that cannot slip without changing the project finish date
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ENG209 Week_11
What is CPM? CPM calculates The longest path of planned activities to the end of the project The earliest and latest that each activity can start and finish without
making the project longer Determines “critical” activities (on the longest path) Prioritize activities for the effective management and to shorten
the planned critical path of a project by: Pruning critical path activities “Fast tracking" (performing more activities in parallel) “Crashing the critical path" (shortening the durations of critical path
activities by adding resources) 11
ENG209 Week_11
Benefits of CPM Useful at many stages of project management Mathematically simple Give critical path and slack time Provide project documentation Useful in monitoring costs
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Limitations to CPM Clearly defined, independent and stable activities Specified precedence relationships Over emphasis on critical paths Deterministic CPM model Activity time estimates are subjective and depend on judgment PERT assumes a beta distribution for these time estimates, but the
actual distribution may be different PERT consistently underestimates the expected project completion time due to alternate paths becoming critical 13
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The CPM Approach
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CPM Dictionary Activity: A task which must be performed to complete the project i.e. : assamble, inspect and test Represented by an arrow Every activity needs a spesific durtion, cost or both of them. Every activity has a start time and finish time. ACTIVITY i
i DURATION (ARROW DIAGRAM)
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ENG209 Week_11
ACTIVITY A
FLOW CHART
ACTIVITY B
(PRECEDENCE DIAGRAM)
CPM Dictionary ï‚— Event: Signals the beginning or ending of an activity
Designates a point in time Represented by a circle (node) EVENT 1
ACTIVITY TIME
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ENG209 Week_11
EVENT 2
CPM Dictionary Duration(D) :The duration is needed for actualising an
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activity Early Start (ES) : the earliest date a task can start Early Finish (EF):the earliest date a task can be completed Late Start (LS) :the latest date a task can start without delaying the project and date Late Finish (LF) :the latest date a task can finish without delaying the project end date
ENG209 Week_11
CPM Dictionary Float (slack) :
amount of time that a task can be delayed without causing a delay to: subsequent tasks (free float) project completion date (total float)
Path :
A connected sequence of activities leading from the starting event to the ending event Critical path : the sequence of activities which add up to the longest overall duration. It is the shortest time possible to complete the project. Critical activity : activity with zero float 18
ENG209 Week_11
CPM Dictionary Network :
Shows the sequential relationships among activities using nodes and arrows Activity-on-node (AON) : Nodes represent activities, and arrows show precedence relationships Activity-on-arrow (AOA) : Arrows represent activities and nodes are events for points in time
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ENG209 Week_11
DEFINITIONS A must finish before B
( Act. on Arrow )
A
( Act. On Node )
B
A
A A&B must finish before C
A
C
C
A&B start simultaneously
B
B
A must finish before C
A
C
A&B must finish before D B
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B
D
A
C
B
D
A
A&B must finish before C. A&B must finish before D
C
B
A must finish before D
A
C
B
D
A
D
B
E
C
F
D
A
D
A &B&C must finish before E B
C must finish before F
E
C
F
A must finish before B A must finish before C C&B start simultaneously B&C must finish before D 21
ENG209 Week_11
B
C A
B
D
A
D C
Identify dummy It is used when two or more activity have the same starting and
ending event.
Boil the water Fill water and milk to the cup
1
2
3
WRONG!!!!!
Worm the milk
There could be just one activity between two event. Boil the water
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DUMMY Fill water and milk to the cup
1
2 Worm the milk
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3
CORRECT√√√
Logic dummy If there is a comman event between two independent series activity, there could be
logic error. i.e: We got an offer for a new job and operator training is needed. As soon as operator start to working and machine is installed , operator training will begin. We wont spend extra time for machine investigation. It will start as soon as machine is installed. Machine setup
Machine investigation
WRONG!!!!!
Hiring operator
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ENG209 Week_11
Operator training
Logic dummy If there is a comman event between two independent series activity, there could be
logic error. i.e: We got an offer for a new job and operator training is needed. As soon as operator start to working and machine is installed , operator training will begin. We wont spend extra time for machine investigation. It will start as soon as machine is installed. Machine setup
Machine investigation
DUMMY
Hiring operator
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ENG209 Week_11
Operator training
CORRECT√√√
NETWORK ï‚— Shows the sequential relationships among activities using nodes
and arrows D B
H
A C
E
FLOW DIAGRAM
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B
F
D
F
A
H
G C
E
G
PRECEDENCE DIAGRAM
NETWORK Questions to prepare activity network;
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Is this a Start Activity? Is this a Finish Activity? What Activity Precedes this? What Activity Follows this? What Activity is Concurrent with this?
ENG209 Week_11
Example: Laddering A 10 km
B 10 km
C 10 km
Pipes will be lied along install 30 km. Assumption: We have one kit for each activity; Excavate (EX) Lie pip (LP) Back-fill land (BF) 27
ENG209 Week_11
Example: Laddering 1
EX.
LP
2
3
BF
4
EX.
5
Part A 7
LP
6
BF
7
Part B EX.
8
LP
9
BF
10
Part C
****If the activities order serial, only one of the kits will be working when the others are waiting.******
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ENG209 Week_11
Example: Laddering EX Part A
Part B
Part C
1
4
7
2
EX
EX
5
LP
LP
3
6
LP 8
9
BF
BF
10
BF
****If we order activity like in the shape, it is not possible to complete the works. Because there is only a kit for every work.*** 29
ENG209 Week_11
Example: Laddering EX A 1
2
LP A
3
BF A
DUMMY
EX B
LP B 4
DUMMY
5
6
7 DUMMY
BF B EX C
8
LP C
9
BF C
10
****We can complete the project as soon as possible and using sources efficiently with help of dummy variables.*** 30
ENG209 Week_11
CPM Rules 1. Two nodes can be connected by at most one arc.
DUMMY
WRONG!!!!!
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CORRECT√√√
CPM Rules 2. Every preceeding activity of an event must be completed before succeding event start. A
D
B E C
***D and E can not start before A,B and C was completed.*** 32
ENG209 Week_11
CPM Rules 3. In a network time flow always actualises from right to the left.
LOOP
****You must avoid from vicious circle**** 33
ENG209 Week_11
CPM Rules 4. Arrows doesn’t protract depending on duration. 5. Every event has a spesific number. 6. There is always a starting and an ending event. 7. You must avoid from unnecesary dummy activities. 8. The node representing the completion of an activity always has a larger number than the node representing the beginning of an activity.
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ENG209 Week_11
Example 2: Draw the CPM network according to given information. Network beginning event is starting event for A. When A finish, C and D will start. When B finish,F and E will start. When C finish, G will start. When D,F and G finish, project will be completed.
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ENG209 Week_11
Network beginning event is starting event for A. When A finish, C and D will start.
Example 2:
When B finish,F and E will start. When C finish, G will start. When D,F and G finish, project will be completed.
D
C
A
G
E
B
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F
Example 3:
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ACTIVITY
START EVENT
FINISH EVENT
A
1
2
B
1
3
C
1
5
D
2
4
E
2
6
F
3
4
DUMMY
3
5
G
3
6
H
4
6
I
5
6
ï‚— Draw the CPM network according to given information. ENG209 Week_11
ACTIVITY
START EVENT
FINISH EVENT
A
1
2
B
1
3
C
1
5
D
2
4
E
2
6
F
3
4
DUMMY
3
5
G
3
6
H
4
6
I
5
6
Example 3:
E
D
2
A
4
H
F
1
B
G
3
6 I
C 38
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5
Example 4:
39
WORK
Duration (days)
Precedence
A
4
-
B
7
A
C
5
A
D
4
B
E
8
-
F
8
B, C, E
G
16
-
ENG209 Week_11
Example 4: Work
Duration (Days)
Precedence
A
4
-
B
7
A
C
5
A
D
4
B
E
8
-
B
F
8
B, C, E
7
G
16
-
1
A 4
Activity on Arrow view
5
E 8 G 40
ENG209 Week_11
16
4
3 C
2
D
4
F 8
5
Example 4: A
START
B
D
C
F
E
G 41
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Activity on Node view
Work
Days
Precedence
A
4
-
B
7
A
C
5
A
D
4
B
E
8
-
F
8
B, C, E
G
16
-
FİNİSH
CPM Calculations • How does the Critical Path Method calculate the project’s finish
date? • Forward pass calculation calculates Early Start and Early Finish date
• Backward pass calculation calculates Late Start and Late Finish dates
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ENG209 Week_11
CPM Calculations • By the forward pass and backward pass we can find; • Critical / Uncritical events • Critical path • Float and total float • P.S: Backward pass calculations cannot be done before forward
pass calculations. Finish Time ?
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ENG209 Week_11
FORWARD PASS • It is done from starting to the ending. • Early Start (ES) and Early Finish ( EF ) times are calculated for every event. • The early finis time of precedence events determine the early start time of all
succeding events. 0
2
5
A 2 0
6
11
B 1
15 E 4 15
0
Finish 15
Start 0
5 D 5
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Forward Pass ENG209 Week_11
5
11 C 6
11
13 F 2
FORWARD PASS ES=3
ES=10
ES
EF D Activity A
ES=9
Early Start (ES) = Latest related early date of all immediate predecessors
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ES= immediate Predecessors’ ES max Early finish (EF) = Early Start + Duration EF= ES + D ENG209 Week_11
BACKWARD PASS It is done from ending to the starting. Late Start ( LS ) and Late Finish ( LF ) times are calculated for every event. The Late start time of succeding events determine the late start time of
preceeding events. 0
2
5
A 2 0
0
8
6
11
B 1 10
10
15 E 4
11
15
11
Start 0
15
Finish
0
0
5
5
D 5 0 46
15
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11 C 6
5
5
11 13
11
13
15
F 2 15 Backward Pass
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BACKWARD PASS LF=3 D
LF=10
Activity A LS
LF
LF=9
Late Finish (LF) = Earliest related late date of all immediate successors
LF= immediate Successors’ LF min Late Start (LS) = Late Finish – Duration LS= LF-D 47
ENG209 Week_11
BACKWARD PASS ï‚— The purpose of backward pass is to find the float.
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Float (Slack) Project Float (slack) : Amount of time project can be delayed
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without delaying externally imposed project completion date. Total Float (slack) : The amount of time an activity can be delayed without delaying project end date. Critical path activities have zero float. Knowing float helps in better allocation of resources. If project is behind an imposed external date, then project will have negative float.
ENG209 Week_11
Float (Slack)
Backward Pass
ES
EF
LS
LF
ES : Early Start LS : Late Start EF : Early Finish LF : Late Finish
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Float = LS-ES
Forward Pass
OR
Float = LF-EF
Float (Slack) 0
2
5
A 2 0
0
8
6
11
B 1 10
10
15 E 4
11
15
11
Start 0
15
Finish
0
0
5
5
D 5 0
11
ENG209 Week_11
11
C 6 5
5
13 F 2
11
ï‚— What is the total Float for activity A? 51
15
13
15
15
15
Float (Slack) 0
2
5
A 2
6 B 1
8
10
10
ES
ES
EF
LS
LF
11
EF 0
LS
2
8
A
Total float = LF-ES-D = 10 – 0 – 2 = 8 ENG209 Week_11
10
Float Float
52
LF
A
Critical Path • Longest duration path in a Network Diagram • It is the shortest time to complete the project • It helps to determine the focus for project management efforts to
capacity control, cost control and time optimization. • Near critical path is close in duration to critical path • Closer the near critical and critical paths are, the more risk project has
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ENG209 Week_11
Activities on Arrow - Forward Pass 1 ESx
X
2
tx
Y
3
ty
EFx
11
EFy
B
ESy
1 0
7
A
C
2
4
5
4
8 G ENG209 Week_11
4
F
4
8
11 E
54
D
3
16
5
19
Activities on Arrow -Backward Pass 1
X
2
tx
Y
3
ty
LFx
LSx
11 11
LFy
B
LSy
1 0
0
7
A
C
2
4
4
5
4
8 G ENG209 Week_11
4
F
4
8
11 11
E
55
D
3
16
5
19 19
Activities on Arrow – Critical Path 11 11
Total Float = Tyg – ( Txe + t ) TB=0B
Slack = Tye – ( Txe + t )
7
SB=0
TB=4D
3
4
TB=0
SB=4
SB=0 1 0
TB=0A t=4
SB=0
0
Txe Txg
2 4 Tye
TB=2C 5
SB=2
4
TB=0F 8
SB=0 11 11
5
19 19
Tyg
TB=3 SB=3
E 8 G 16
ENG209 Week_11
4
TB=3 SB=3
56 Critical path activities have zero float. There colud be Critical path more than one.
Example 3: For a construction project the relationship of works and duration of each work is given. Draw the CPM network according to given information. Find the critical path.
57
ENG209 Week_11
Example 3:
58
Works
Duration (months)
1-2
5
1-3
7
1-4
9
2-4
6
2-6
12
3-5
6
4-5
5
4-6
8
4-7
9
5-8
13
6-7
4
7-8
6
ENG209 Week_11
Works Months
Example 3: 5
19 19
5 2
TF=0 FF=0 5
12
5
TF=3 FF=0 3 6
6
5 7 9 6 12 6 5 8 9 13 4 6
TF=0 FF=0 29 29
TF=0 FF=0 13 TF=0 FF=0 5
7 10 TF=3 FF=3 16 16 ENG209 Week_11
7
8
4
11 11
7
59
4
9 TF=3 FF=3 9 TF=2 FF=2
0
6
23 23
TF=0 8 FF=0
TF=0 6 FF=0
1 0
TF=0 FF=0
TF=2 FF=2
1-2 1-3 1-4 2-4 2-6 3-5 4-5 4-6 4-7 5-8 6-7 7-8
CP1= (1-2), (2-4), (4-6), (6-7), (7-8) CP2= (1-2), (2-4), (4-5), (5-8)
Example 4: Activity
Precedence
A
---
16
B
----
20
C
---
30
D
B
E
B
10
F
A
15
G H I
Duration (days)
b) c)
15
D D
a)
3 16
E,F,G
12
d) e)
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ENG209 Week_11
Create network diagram. Find early start time for every activity. Find late start time for every activity if the project is completed in the minumum time. Find critical path. Find the slacks.
Activity (days)
Example 4: a) Flow diagram
Precedence
A
---
16
B
----
20
C
---
D
B
E
B
10
F
A
15 D
3
D
16
I
E,F,G
F
2
30 15
G H
12
5
A 1
B
E 3
D C
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ENG209 Week_11
G
Duration
I
4 H 6
b) Find early start time for every activity Event
Precedence
ES
Time
EF
1
-
-
-
0
2
1
0
16
16
3
1
0
20
20
4
3
20
15
35
5
2
16
10
38
3
20
15
4
35
3
1
0
30
4
35
16
5
38
12
6
62
51
The early finish time of the project is 51 days.
ENG209 Week_11
b) Find late start time for every activity Event
Succeeding events
LF
6
-
51
5
6
51
12
39
4
5
39
3
35
6
51
16
4
35
15
5
39
10
2
5
39
15
24
1
2
24
16
0
3
20
20
6
51
30
3
63
ENG209 Week_11
Time
LS 51
20
b) Find critical path.
64
Events
EF
LS
1
0
0
2
16
24
3
20
20
4
35
35
5
38
39
6
51
51
In the table the events which early finish time equals late start time create critical path. Critical path: 1 3 4 6 ENG209 Week_11
b) Find the slacks. Activity
ES
LS
Time
Slack
1-2
0
24
16
8
1-3
0
20
20
0
1-6
0
51
30
21
2-5
16
39
15
8
3-4
20
35
15
0
3-5
20
39
10
9
4-5
35
39
3
1
4-6
34
51
16
0
5-6
38
51
12
1
Activity 2-5 can delay 8 days without extend the project time. 65
ENG209 Week_11
Example 5: Company is planning to product a new mp3 player. Managers want to know; When the project will be completed? Which activities are critical? Starting and ending time of every activity.
66
Code
Activity
Succeding
Time (days)
A
Ä°dentification of product features
-
30
B
feasibility study
A
8
C
prototype production
B
8
D
raw material procurement
B
5
E
Prepare final design
H
2
F
Production
D,E
25
G
Personnel training
A
10
H
Personnel offers about prototype
C,G
3
I
Sales training
E
5
J
Ä°dentifying marketing mix
A
5
K
promotion campaign
I,J
15
Finish the project
F,K
2
L
ENG209 Week_11
Example 5: D 5 B 8 C 8 A 30
G 10
J 5
H 3
E 2
F 25
L 2
I 5
K 15
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ENG209 Week_11
Example 5: 30;38 30;38 0;30 0;30
A 30
D 5
B 8 G 10 J 5
30;40 36;46
30;35 56;61
C 8
38;43 46;51
38;46 38;46
46;49 46;49
H 3
E 2 49;51 49;51
51;56 56;61
51;76 51;76
76;78 76;78
F 25
L 2
I 5
56;71 61;76
K 15
68
ENG209 Week_11
Example 5: • If activity A delays 1 day, when the project will be completed? • A is an critical activity. So all acitities succeding A will be
postponed 1 day. And the project time will lenght out 1 day. • If activity D delays 7 day, when the project will be completed? • D is not a critical activity. So we must think the slack of this
acitivty. Because the slack of this activity is 8 days, 7 days delay wont effect the project completion time.
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ENG209 Week_11
Example 5: • If activity D delays 7 day and activity J delays 25 days when the project will
be completed? • Both of the activiy are not critical and delay time is smaller than slack time. So project completion time.wont be effected. • If activity K delays 6 day, when the project will be completed? • K is not a critical activity. So we must think the slack of this acitivty. Because
delay time is bigger than slack project completition time will be effected. • Project time will length out 1 day (6-5=1) • Activity K is a critical activity from nowç And critical path will change. 70
ENG209 Week_11