Why CPM is not good enough to plan and manage ...

Why CPM is not good enough to plan and manage Projects? Tapan Bagchi, Bimal Jena and Kaushik Sahu KIIT Bhubaneswar India

Presented at IEEM IEEE Conference, Dec 10-13 2017 Singapore

CCPM Overview

Bagchi Jena Sahu IEEM IEEE Conference Singapore

CPM network—the tradition in Project planning Order furniture Locate facilities

Furniture setup

2

6

1

Move in

Remodel

5

S

Interview

3

Hire and train

4


7

A Critical Path constructed with buffers still has performance problems… X

FB

X

FB

PB

X

X

FB

X

FB


X = shared resources FB = feeding buffer PB = project buffer

Resourcing the Project • CPM typically uses the infinite resource assumption • Reliance on spot contracts

• Types of resources • plant • Labour; experts; designers • Space

• Resource levelling • Generally uses slack to smooth resources Bagchi Jena Sahu IEEM IEEE Conference Singapore

Critical Chain Project Mgmt comes from the “Theory of Constraints” • • • • •

Identify the constraint (the bottleneck) Exploit the constraint Subordinate rest to the constraint Elevate the constraint Identify the new constraint 5:Design

2:Dev

4:Dev 2:Dsn 3:Proto 3:Proto 2:Tst In project 2:Dsn Management, the4:Dev Critical Chain is the bottleneck —it prevents the project from finishing sooner Bagchi Jena Sahu IEEM IEEE Conference Singapore

The “Critical Chain” Method is different! Theory of Constraints is the basis The Critical Chain is the longest path through the resource constrained network Task execution durations are shrunk  50/50 used in calculations  Project is protected by safety buffer

Not punishing overruns is the rule


Let’s summarize… In CPM we don’t have an effective mechanism for

synchronizing multiple projects without negatively impacting other project work Bagchi Jena Sahu IEEM IEEE Conference Singapore

A closer look at CPM ●Tracks the project based on estimated task due dates ●Reacts when something is late ●REALLY reacts when something on the critical path is late ●Hopes and prays that the project finishes on time


Real Life “Laws” of Project Management 1) Murphy’s Law • What can go wrong will go wrong • When things cannot get any worse, they will • When things appear to be going well, you must have overlooked something

So, estimates in CPM each include Safety Buffer Commitment

Estimates become Commitments Bagchi Jena Sahu IEEM IEEE Conference Singapore

CPM says, start tasks on Early Start Dates! But this leads to resource overload


Time estimation in CPM Well…about 5 days Create list of tasks

+ I am working on another project + I get interrupted a lot

+ Something usually goes wrong So…10 days!

“Safety” built in Project Manager asks, “How long will each task take?” Bagchi Jena Sahu IEEM IEEE Conference Singapore

Further, task times are variable… Individual Task times get skewed Probability of Task Duration 50% 80%

A

B

Which time will the resource give the PM - A or B?

Result: We pad (long) activity times & you’ll never see an “early finish.” Bagchi Jena Sahu IEEM IEEE Conference Singapore

Look closely at the issue of Safety: Estimates vary, so CPM tasks are safety cushioned 50% confidence

Safety is generally built into estimates 10% confidence

2

5

90% confidence

10


Project Duration Variation Task 1

CPM tries to play it safe--

Task 2

Committed Finish Time Task 3

But, since all tasks are scheduled with 90% confidence, why are most projects still delivered late, overbudget, or scope reduced? Bagchi Jena Sahu IEEM IEEE Conference Singapore

Behavioral Problems exist!… The real pattern of our level of effort as a deadline/due date approaches Do time estimates that have a high probability of completion have any other negative affects on human behavior?

And, of course, when will Murphy show up???

X Murphy

Task Scheduled, Available Start Date

Task Scheduled Completion Date

The “Student Syndrome”  don’t start work till Bagchi Jena Sahu IEEM IEEE Conference the deadlineSingapore is on your head!

Another odd behavior of Projects 2) Parkinson’s Law • Work expands to fill the time it is given • “Student Syndrome” – many people will start to fully apply themselves to a task just in the wake of a deadline • Driven by focus on due dates

“As long as I get it done on time, everything is OK!”


Summary of what’s wrong with CPM ●Buffer built into each individual estimate is overkill ●Tracking individual task due dates to indicate project health encourages:  Estimates that are commitments  Work expanding to fill the time available

●Encourages individual ownership of individual commitments rather than team ownership of the project


Unreported Early Finishes occur! Two other phenomena: • Parkinson’s Law - Work expands to fill its time. • The 3 Minute Egg Rule – “It’s not quality if it’s finished before the time is up”

These Two effects come from the same root cause-- We

often lack clear criteria defining when a task is complete Bagchi Jena Sahu IEEM IEEE Conference Singapore

Logical analysis - Summary of key issues Synchronization Mechanism - Inability to handle new projects and committed projects effectively. Project Planning - missing the effect of resource dependencies and errors from time estimates

Project Scheduling - errors of additive rules and releasing work too early Resource Behavior - Unreported Early Finishes, Parkinson’s Law, 3 Minute Egg Rule, Student Syndrome Project Control & Visibility - Utilizing tasks and milestone performance (EVM) as indicators Bagchi Jena Sahu IEEM IEEE Conference Singapore

CCPM targets these problems that exist with CPM: ●Multi-tasking ●Parkinson’s law ●Student syndrome ●Partnering with the resource bases— we don’t issue alerts to the next guy in line ●We shield actual production!


Goldratt’s suggestion: In place of CPM, Use…

Critical Chain Project Management ●CCPM is a way to schedule and track a project that encourages: • An aggressive schedule that makes it more possible to deliver early • Team focus • Team ownership of the team commitment Bagchi Jena Sahu IEEM IEEE Conference Singapore

Project Scheduling by Critical Chain (CCPM)

1. To protect the due date, CCPM uses a buffer of aggregated safety time called as Project Buffer 2. To protect the longest path, CCPM uses buffers of aggregated safety time called Feeding Buffers


A Critical Chain uses Buffers FB

X

FB

X

FB

X

FB

X

FB

X


PB

X = shared resources FB = feeding buffer PB = project buffer

Effective utilization of safety buffers CCPM says: Do not use safety buffers in each task! Instead use buffers to protect the project

Task 1

Task 2

Task 3

CPM deadline Bagchi Jena Sahu IEEM IEEE Conference Singapore

Effective utilization of safety buffers Do not use up safety buffers in the individual tasks!

Task 1

Task 2

Task 3

Use 50/50 times and move the safety buffers to the end to protect the committed deadline Bagchi Jena Sahu IEEM IEEE Conference Singapore

Effective utilization of safety buffers—it reduces project duration Safety Safety

Safety

End

Safety

Remove the safety from the individual tasks Put it where the project benefits Safety Safety Safety Safety

Latest Expected Finish (date you will commit to by CCPM) Bagchi Jena Sahu IEEM IEEE Conference Earliest Possible Finish

Singapore

Buffer Placement: two places ●Project Buffer  Between the last task of the aggressive project schedule critical chain and the committed end date

●Feeding Buffers  Protect the critical chain from being impacted by noncritical chain  Place at the end of non-critical chains before they connect to the critical chain


CCPM: Step 1 Create the Network using 50/50 time estimates A) Use average 50/50 task times B) Place tasks at late start

Original CPM times (these include safety cushion “90%”) 10:Design 4:Design

6:Proto

4:Dev 8:Dev

Step 1: Basic Network made by aggressive 50/50 times 2:Dev 5:Design 5:Design 2:Dev 2:Dsn 3:Proto

4:Dev

2:Tst


4:Tst

Step 2 Identify the Critical Chain A) Eliminate resource contention 5:Design

2:Dev

4:Dev 4:Dev 2:Dsn 2:Dsn 3:Proto 3:Proto

2:Tst

B) Identify the Critical Chain The Critical Chain The longest path through the network considering both task and resource dependencies Bagchi Jena Sahu IEEM IEEE Conference Singapore

Step 3 Deal with Uncertainty—add buffers What is the chance of completing whendue “planned”? The Project Buffer protects the project date

Not here! 5:Design 2:Dsn 3:Proto

2 Dev

4: Dev

2:Tst

6.5: Project Buffer

Where else is the project vulnerable to disruptions? Feeding Buffer 5:Design

2:Dsn 3:Proto

2: FB 2 Dev 4: Dev

2:Tst

6.5: Project Buffer

Feeding buffers protect the Critical Chain Bagchi Jena Sahu IEEM IEEE Conference Singapore

planned date

The CCPM Difference CPM Original 4:Design

By CCPM 2:Dsn

4:Develop

10:Design

5:Design

3:Proto

8:Develop

6:Prototype

4:Test

No Resource Contention

Feeding 2:Dev Buffer

4:Dev

Original CPM Estimated deadline

2:Tst

Better Protected

Project Buffer

By CCPM Project gets Shorter


Reporting progress: You monitor buffer use Designer says: “We completed the 2-day task, but we still have 4 days to go on our other task”—what would you do? Projected task time 5:Design

2:Dsn

3:Proto

Today

Buffer consumption

2: FB 2 Dev

4: Dev

2:Tst

6.5: Project Buffer

Projected task times Bagchi Jena Sahu IEEM IEEE Conference Singapore

Project Report CC Complete: 15% PB Consumed: 30%

Creating a Critical Chain Schedule ●Build the WBS

●Identify dependencies ●Gather estimates with 50% confidence • 1 set – 50% • 2 sets – 50% and 90% - check for difference • 1 set – 90% - and cut in half to get to 50% ●Build your project schedule using LATE FINISH (rather than “early start”)  reduces crowding ●Resolve resource contentions (leveling) • Start allocating the resources to the critical chain first! Bagchi Jena Sahu IEEM IEEE Conference Singapore

Creating a Critical Chain Schedule (contd.) ●Identify the critical chain ●Exploit the critical chain to identify any resequencing that can shorten the duration ●Add the Project Buffer to the end of the critical chain ●Add Feeding Buffers to all non-critical chains that feed the critical chain ●Resolve new resource contentions


CCPM review


Buffer Sizing ●There are multiple ways to size the buffers

• 50% of the sum of task durations on the chain • Conservative • Great for first timers – that’s us! • SSQ • Square root of the sum of the squares of the differences • More aggressive


Buffer Management & Control


Take advantage of early finishes— roadrunner handover ● Tasks may actually finish early! ● Treat the transition of tasks as a relay race! ● Keep appropriate people informed that an early finish may be imminent so they can be prepared to grab the baton and run!

Resource buffer


Case Study of CCPM • Example comes from Figure 9.4, Meredith and Mandel’s Project Management text • A two-resource project d, 15 0, 2

f, 14

b, 20

1, 1

2, 11

h, 11 0, 2 Bagchi Jena Sahu IEEM IEEE Conference Singapore

The Resource Constrained schedule


The Resource leveled Schedule


The CCPM for this Project with Buffers


CCPM Focuses on… ●Starting tasks on time ●Completing tasks as aggressively as possible ●Maintaining quality, despite aggressive push ●Amount of Project Buffer that is consumed


CPM vs. CCPM The CPM Way Uses worst-case estimates Protects individual tasks with safety Starts and finishes tasks at scheduled start and finish times

Individual ownership of task completion

Critical Chain (CCPM) Uses average-case estimates Protects project with buffers Starts tasks as soon as predecessors are done, finishes tasks as quickly as possible.

Team ownership of (relay race) Project health is based Project health is on individual task indicated by days used completion up from the project Bagchi Jena Sahu IEEM IEEE Conference Singapore buffer

Does CCPM work? ●Software – BOS, Lucent ●Maintenance – Navy Depots, Israeli Aircraft, Israeli Air force ●Engineering & Construction – ITT, Harris ●Testing – USAF: AFOTEC (C-17, F-15) ●Production Supply – Synergis, Boeing ●Product Development – Lucent, BAE Systems, ITT, Harris, Gudiant, Intersil, P&G ●Hot Steel Melting, TATA Steel JSR, 2006 Bagchi Jena Sahu IEEM IEEE Conference Singapore

Difficulties with CCPM • Initially a pilot project should be attempted • —led by a competent and capable CCPM champion within the company (NASA and TATA did this), one soundly versed in the practice of project management and also trained well in CCPM. • A consultant can advise or coach, the champion alone will identify with the company and pour in passion. • No less critically, top management must ensure that external risks have been addressed and resolved. A fully complete auto factory had once to be shifted off its foundations Bagchi Jena Sahu IEEM IEEE Conference Singapore

CCPM is a useful heuristic… It brings discipline into PM. We are still waiting for its “theory.”

To get more Information on CCPM, ●Excellent white paper http://www.focusedperformance.com/articles/ccpm.html ●Real-life project example http://pqa.net/ProdServices/ccpm/W05002005.html#Intro duction ●Yahoo Discussion Group http://finance.groups.yahoo.com/group/CriticalChain/ ●March 2003 Cutter Journal – lots of great articles http://www.cutter.com/research/freestuff/itj0303.pdf ●A very good book -- “Critical Chain Project Management”, 2nd edition, by Lawrence Leach Bagchi Jena Sahu IEEM IEEE Conference Singapore