TEC 5970 Quality Problem Solving CRITICAL PATH METHOD

TEC 5970 Quality Problem Solving CRITICAL PATH METHOD: A Problem Solving Tool Prepared By Sajan Tuladhar

Discussion Topic • • • Background Project Management What is CPM? Why the CPM? How the CPM? Case Studies Critical Thinking Summary Conclusion References for Further Studies

Background • Walker & Kelly (1957) designed CPM for UNIVAC-I Computer • Applied to build Chemical Plant (1958) • Maintenance shut down at Du Pont (1959) – Reduced unproductive time from 125 to 93 hr • PERT for POLARIS missile program (1958) • Gantt Chart (1910)- Henry Gantt • Integration of CPM, PERT & Gantt

Project Management • The application of knowledge, skill, tools & technique to a broad range of activities in order to meet the requirements of the particular project • Is a temporary endeavor undertaken to achieve a particular aim • Types of problems – Development of a new product – Improvement of an existing product – Elimination of a problem with an existing product

Project Management (Contd…) • SMART Objectives – Specific, Measurable, Achievable, Realistic, Timeframe • Basic Five Process Groups – Initiating, Planning, Executing, Controlling & Closing • Zimmerman’s Law: Regardless of whether a mission expands or contracts, administrative overhead continues to grow at a steady rate.

Project Management (Contd…) Time Resources People $ Eqpt. Facil. Mat. Inf. Tec. Performance Cost

Project Management (Contd…) Questions About the Project - How long will the entire project take to complete? - Which activities determine total project time? - Which activity times should be shortened, if possible, or in other words, how many resources should be allocated to each activity?

What is CPM • A technique for planning the most efficient way to achieve a given objective by determining the activities and events required and showing how they relate to each other in time. • Diagram consists of arrows (Activities) & circles (Events). Activities consume resources and time; events do not, rather they mark points in time when activities begin or finish. Length of an arrow has no relevance.

What is CPM • A The CPM network has one starting event and one ending event. • Each activity is bounded by two events, one at the tail (starting point) and one at the head (ending point). Activity Event 1 i Foundation (A) 5 months j Super structure (B) 2 Duration i 3 8 months j

Why CPM • Formally identifies tasks which must be completed on time for the whole project to be completed on time • Identifies which tasks can be adjusted if resource needs to be reallocated to catch up on missed tasks • Determines both the early start and the late start date for each activity

Why CPM • The greatest asset of CPM is its portrayal of critical activities, giving the project manager forewarning of where he or she might expect schedule problems • Helps the project manager analyze a project before, during, and after operations

How CPM Specify the activities Estimate activity completion time Determine the sequence of the activities Identify the Critical Path Draw the Network Diagram Update the CPM Diagram

Type of CPM Activity on Arrow (Ao. A) A B 1 Start E 2 6 4 End Dummy C 3 5 F D Activity on Node (Ao. N) Start 1 2 4 3 6 5 End

How CPM Early Start Duratio n Early Finish Task Name Late Start Slack Late Finish Earliest start time (ES): The earliest time at which the activity can start given that its precedent activities must be completed first. Earliest finish time (EF): It equals to the ES time for the activity plus the time required completing the activity. Latest finish time (LF): The latest time at which the activity can be completed without delaying the project. Latest start time (LS): It equals to the latest finish time minus the time required to complete the activity. Slack time (or, Float): It is time between its earliest and latest start time, or between its earliest and latest finish time. Slack is the amount of time that an activity can be delayed past its earliest start or earliest finish without delaying the project.

Type of CPM Activity on Arrow (Ao. A) A B 1 Start E 2 6 4 End Dummy C 3 5 F D Activity on Node (Ao. N) Start 1 2 4 3 6 5 End

Flat Tyre Repair Problem Activity Description Prerequisites Duration (min) A Remove the wheel with the flat tyre - 2 B Bring spare wheel to car - 1 C Fit spare wheel to car A, B 2 D Repair tyre A 3 E Place repaired wheel in boot D 1

Ao. A Diagram 4 D, 3 1 A, 2 B, 1 2 3 Calculation E, 1 5 Track 1: A, D&E =2+3+1= 6 min (CP) Track 2: A & C = 2+2 = 4 min Dummy C, 2 (0) Track 3: B & C= 1+2= 3 min Critical Path Ao. N Diagram A, 2 D, 3 Start E, 1 Finish C, 2 B, 1

CPM Software Microsoft Project (MSP) Microsoft Visio Earl y Star t Dura tion Earl y Finis h Earl y Star t Late Finis h Lat e Star t Task Name Lat e Star t Earl y Star t Dura tion Slac k Earl y Finis h Late Finis h Earl y Finis h Task Name Slac k Late Finis h Earl y Star t Dura tion Earl y Finis h Task Name Lat e Star t Slac k Late Finis h Critical Path Calculator Link Lat e Star t Slac k Late Finis h

CPM vs. PERT vs. Gantt CPM PERT E(4) 3 A(3) 4 D(3) 1 B(2) 2 F(1) Optimistic time= O Pessimistic time= P Most likely time= M Expected time = T E = (O+4 M+P)/6 5 C(1) Note: PERT & Gantt are beyond the scope of this paper Gantt Chart

Integrating Problem Solving Tools • CPM/PERT/Gantt • CPM & Control Chart B, 10000 Balls Production, 2 hr CPM Control Chart

Critical Thinking Beware • Task durations are estimates • Task durations are fabrications • Task durations depend upon the quality of conversations Precaution • Investigate the level of effort for every task on the critical path. Adjust buffers in accordance with • Measure the performance of your planning practices as a basis for eliminating the sources of task variability • Include performers in planning conversations to give them practice for the inevitably uncertain future

Case Studies Levan Viaduct Repair Project • 500 meter long & 49 spans • Two option– repair the viaduct – close down the line and re-route all traffic • Challenges –To deliver the project within a given budget –To have no accidents or incidents during viaduct construction –To establish good relationships with the community and to respect the local environment –To ensure the efficient procurement of the steel that was essential to the project to minimize disruption to passengers and freight

Levan Viaduct Repair Project • Problem solving Tool Used • Critical Path ABE = 11 months • Focus on Pier repair work • Completed on July 16, 2006 (On Time) • Project cost reduced to ₤ 14 million from estimated ₤ 20 • Historic and impressive landmarks for another 140 years

Apollo Mission to The Moon “I believe that this nation should commit itself to achieving a goal, before this decade is out, of landing a man on the moon. . . “ J. F. Kennedy, May 27, 1961

Apollo Mission to The Moon • • • 10000 separate tasks Which had to be done first? Which could be done concurrently? What were the critical sequences? Vital questions such as these had to be answered in building the network of tasks leading to a lunar landing

Apollo Mission to The Moon Sub divide into manageable portion • Determination of the environment in cislunar space and on the lunar surface • The design and development of the spacecraft and launch vehicles, the conduct of tests and flight missions to prove these components and procedures; • The selection and training of flight crews and ground support to carry out the missions.

Apollo Mission to The Moon On July 20, 1969, just eight years after Kennedy's speech, Apollo 11 landed two men on the moon. NASA used the critical path method to help determine an efficient schedule for the tasks that led to the moon landing.

Summary CPM is an effective & powerful tool of assessing: • Sequences of work activities involved in the project • Determine the shortest project duration • Resources allocation in the project • Planning, execution & controlling

Conclusion • CPM is most useful and effective for routine type project works • Its capability enhanced when used with other problem solving tools • Highlight the critical activities where serious attention must be taken • Estimating task duration is crucial

References for Further Studies Busch, D. H. (1991). The new critical path method. Chicago: Probus Publishing Company. Giammalvo, P. D. , Djodi, F. , & Evi, D. (1996). Implementation of a continuous process improvement program using data from CPM schedules. Project Management Journal. Kerzner, H. (2003). Project management: A systems approach to planning, scheduling, and controlling. New Jersey: John Wiley and Sons. Web Search Engines. Key words – Critical Path Method or CPM or Critical Path Analysis or CPA

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