12 Critical Chain Project Management

7/23/2019 12 Critical Chain Project Management

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CRITICAL CHAIN PROJECT MANAGEMENTCRITICAL CHAIN PROJECT MANAGEMENT

(CCPM)(CCPM)



Let us start….

– Time and Cost Overruns

•• But Why?But Why? – Tight deadlines

– oo many comp ex t es

– Too many uncertainties

–

– Poor training…..

•• How to solve?How to solve? – Address these issues

– Provide cushions



Reasons for variabilityReasons for variability

– – Lead time variability is more dangerous than long leadLead time variability is more dangerous than long leadtimestimes

– – Uncertain short deliveries leads to more buffers thanUncertain short deliveries leads to more buffers than

known long deliveriesknown long deliveries – – A project with very high (and equal) asset utilisation & A project with very high (and equal) asset utilisation &

tight planning will have more variability and costtight planning will have more variability and cost

– – TreatTreat Variability Variability as the most important performanceas the most important performance

measuremeasure

– – Develop systems that minimise variabilityDevelop systems that minimise variability



But…

Projects?



How much buffer in project planning?

How do we estimate project duration?How do we estimate project duration?

•• Past DataPast Data•• o Down or Bottom u a roacho Down or Bottom u a roach

•• Cushions for uncertaintyCushions for uncertainty

•• Activit recedence network techni ue Activit recedence network techni ue

•• the activity??the activity??



How much buffer in project planning?

•• How confident do you feel about the taskHow confident do you feel about the task

es ma es you ma ees ma es you ma e

– 30% sure

– 50% sure

– …

•• Most people would like to beMost people would like to be atleastatleast 80% sure80% sure

of delivering on their commitmentsof delivering on their commitments

•• at oes t at mean or tas est mat onat oes t at mean or tas est mat on



What does that mean for task estimation?

•• means every as as some sa e ymeans every as as some sa e y

•• “If you want your estimates to be reliable and career “If you want your estimates to be reliable and career

safe then have safety incorporated in the activity” safe then have safety incorporated in the activity”

••

task, the greater safety is incorporated in your task.task, the greater safety is incorporated in your task.



This is What a Project Looks like?



ro ect urat on

TheoryTheory

6 10 146 10 141212

•• What is the effect?What is the effect? ActualActual

8 10 308 10 302626

The effect is that the typical cushions you provide onThe effect is that the typical cushions you provide on

Each activity as high as 120Each activity as high as 120--180%180%



So….

given during planning is only around 15-20%,studies have shown that normall much hi her

buffer… even up to 200% is given

• Where are those buffers? – Why projects delay even after these buffers?



Why Failures?Why Failures?

PROJECT

ORGANISATION



PROJECTPROJECT

as ageas age

PROJECTORGANISATION



Reasons for wastage

– Wrong choice

•• Com letel unrelated to strate & oals of Com letel unrelated to strate & oals of or anisationor anisation

– Mismatch between market & process structure

– Misalignment with organisational strategies – Behavioral issues



Behavioral Realities in Project Environment

– Commitments of duration and total cost of a project are based upon adding up the

duration and cost of individual tasks

’ ’

– Work expands to fill its time

•• 33--Minute EGG RuleMinute EGG Rule – t s not qua ty t s n s e e ore t me s up

•• Self Self--protectionprotection – People fail to report early finishes out of fear that management will adjust their future

stan ar s

•• Dropped batonsDropped batons – Early finishes may not lead to the start of next activity as people assigned next activity

are engage somew ere e se

•• Student syndromeStudent syndrome-- delay the start of tasks until you absolutely have todelay the start of tasks until you absolutely have to

•• Hockey Stick SyndromeHockey Stick Syndrome

– – Waiting to start a task due to more important work at handWaiting to start a task due to more important work at hand



Contradictions in Project Management

What we want... ...and what we actually do

To finish projects on time We try to finish separate tasks on

time

To take more projects; We try to make our people more

efficient

To decrease the time for project

accomplishment;

We try to decrease the time for task

accomplishment;

comparatively small costs;

To make customer happy; We fight with each other on resource

In this column we have only

global, company-In this column we have

level factors;

factors!



Project Dilemma

Avoid Effect of Avoid Effect of

Parkinson’sParkinson’s

LawLaw

MinimiseMinimise

ProjectProjectScheduleSchedule

without bufferswithout buffers

ManageManage

ProjectProject

ea meea me (safety)(safety)

coconflnfl

Ensure ProjectEnsure Project

PromisePromise

ictict

Provide forProvide for

adequateadequateBuffersBuffers

MurphyMurphy



o ern ro ec anagemen :

Critical Chain Project Management

• The TO philosophy applied to project

management attempts to remove the

, - ,

under-performance projects) by attacking

• What is TOC Philosophy?



Theory of Constraints

•to a process improvement philosophy)

• Organizations live or die as systems, not as

processes• Success or failure is a function of how welldiff t t i t t ifferent component processes interact wone another



eory o onstra nts

• Systems are analogous to chains, ornetworks of chains

• Like a chain, a system’ s performance is

link

• The weakest link is the system’ sconstraint




– A large number of undesirable effects will be caused

by a relatively small number of core drivers

– Eliminating a very few core problems can result in ahuge improvement



TOC and Projects

–• Repeating a basic principle of TOC

–

by a relatively small number of core drivers – Eliminating a very few core problems can result in a

huge improvement




• Uncertaint alwa s resent – it doesn’ t o awa • Take the safety out of each of the critical path tasks and lump

them into a safety net at the end of the project

•

tasks that can suffer from the constraint (constraints = time andresources)

resources are available




1. Identify the system constraint

3. Subordinate everything else4. Elevate the constraint

5. Go back to Step 1, but beware of “inertia”



Why after all these cushions project get delayed?Why after all these cushions project get delayed?



ower o ggrega onower o ggrega on



Remove safety time from individual activities

Conventional Project Schedule Task buffers(safety time) are hidden

• Safety buffers

Job 2

Job 1within individual activities

•

Job 4

o

Critical Chain Schedule

Buffers are pooled,

and made explicit

Project Buffer ,

to protect the completion date of the project.



• Feeding buffer on the non-critical path

Critical Chain

path

Feeding Buffer Project Buffer

If Slack remains,then schedule as

late as possible

delays on non-critical paths



• Resource buffers

–critical tasks

– Scheduled idle time can provide better info about resource’s

Buffer

r ca a n

Alert Wkr A

ProjectBuffer Alert Wkr B

Buffers Alert Wkr C




• ritical hain- set of tasks which determines overall project

duration, taking into account both precedence and resource

dependencies; improvement along Critical Chain will likely resultin improvements to the project as a whole; improvements

• Project buffer - protects project commitment dates from

fluctuations on the Critical Chain

Feeding buffer eeding buffer -

feeding tasks; provides the possibility for Critical Chain tasks to

start early

• Resource buffer -esource buffer

availability of required resources; also provides the possibility forCritical Chain tasks to start early

C iti l Ch i P j t M t




Original Critical Path

1 2 3 4 Project Buffer

Buffer

(Safety removed from individual tasks)



C iti l Ch i P j t M t




• About Buffers – Identify the points at which to place project, feeding,

– Buffer sizes determined approximately, based either onaverage task duration estimates, or a combination of

average and worst-case duration estimates – Individual buffer sizes can be adjusted based on

intuitive assessment of risk

– Buffer insertion may cause the Critical Chain, and

hence the project completion date, to be pushed later





helps minimize project duration and WIP, and

maximize the chance of on-time com letion

• Simple project with critical path




6 8 4 10

A D G J

8 6 12 108

C F I L6 10 16 6 Calculated critical path is

C-F-I-L-M = 46 days

A D G J

6 8 4 10

8

Activity H and I

cannot be done

simultaneously

MB E H K 8 6 12 10

6 10 16 6

Suppose H & I share a common resource?Suppose H & I share a common resource?

C F I LCalculated critical chain is

B-E-H-I-L-M = 56 days





6 8 4 10

A D G J

8 6 12 108

C F I L6 10 16 6 Calculated critical path is

C-F-I-L-M = 46 days

• Realistic critical chain for the ro ect

A D G J

6 8 4 10

8

Activity H and I

cannot be done

simultaneously

MB E H K 8 6 12 10

6 10 16 6

C F I LCalculated critical chain is

B-E-H-I-L-M = 56 days



Replacing safety time with Buffers

• Critical chain with appropriate project and feeding

buffersGoldratt suggests that a rough ruleof thumb to assume safety time

equals about half of an activity’s

A D G JFeeding

Buffer

=7 days

completion time

MB E H K Feeding

Buffer

=

Project

Buffer

=

4 3 6 54

28

Feeding Critical chain B-E-H-I-L-M = 28 days3 5

83

=4 days

13Slack = 1 days

ro ect u er = ays

Project completion deadline = 42 days

Critical chain process



Critical chain process

“ ” “ ”of completionof completion

•• Add Add project buffer project buffer at the end of the project.at the end of the project.

•• Add Add feeder buffersfeeder buffers where nonwhere non--critical paths mergecritical paths merge

with the critical chainwith the critical chain•• Add Add resource buffers resource buffers

•• Schedule nonSchedule non--critical activities at their latest startcritical activities at their latest start



• ene s o r ca a n – Better project status info allows managers to set clear

priorities

– u er managemen e ps resource manager o a oca e

resources to those projects most in need – Focus on the key tasks and resources

• a enges o r ca a n – Doesn’t provide any objective basis of determining buffer size

(include risk management) – r ca a n pro ec managemen presen e as amethodology

• Culture change may be difficult

applicable to your environment within border projectmanagement methodology



Air Control Project—Critical Path Network



Air Control Project Gantt Chart

Air-control project - Resources



Air control project Resources

RobRob

CarlyCarly

yanyanLaurenLauren

Connor Connor RyanRyan

DawnDawnKevinKevin

Issues?Issues?

88--55



—With Resources Limited



Air Control Pro ect

Schedule With Resources



Air Control Project—Critical Chain Network

“ ”




Find theFind the critica c aincritica c ain




AddAdd ro ect bu er ro ect bu er at the end of the ro ect.at the end of the ro ect.




AddAdd feeder buffers feeder buffers where nonwhere non--critical aths mer e with the critical chaincritical aths mer e with the critical chain

88--88

12 Critical Chain Project Management

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