Lecture 11 - critical chain

1 IPPD 3/14/00 critical ChainLecture 11: critical chain and the design processIPPD 3/14/00 critical ChainBackground These slides were borrowed from apresentation given by Steven Cook Based on work done in an LFM project withITTIPPD 3/14/00 critical ChainTOC Fundamentals The goal of a manufacturing organization is notto keep machines busy, employ workers,provide good customer service, or be at theleading edge of technology. It is to makemoney, now and in the future. Dr. Eli GoldrattFrom presentation by Steve CookIPPD 3/14/00 critical ChainConventional Inventory is an asset.

2 Idle resources are wasteful. Big batches minimize cost. High product margins always mean higherprofits. The most profitable plant is a balanced plant. To reduce cycle time we must increasecapacity Overall performance is the sum of all localperformance. From presentation by Steve CookIPPD 3/14/00 critical ChainSimplified Manufacturing Example An improvement to any area other than SpreadCheese and Toppings makes the pizza shop nomore moneySpread SauceMake DoughSpreadCheese andToppingsCookSlice102030405060 Number of Pizzas per HourBottleneckFrom presentation by Steve CookIPPD 3/14/00 critical ChainThe Five Focusing Steps of TOC 1.

3 IDENTIFY the system s constraint(s) 2. Decide how to EXPLOIT the system sconstraint(s) 3. SUBORDINATE everything else to theabove decision 4. ELEVATE (if necessary) the constraint 5. If, in the previous steps, a constraint hasbeen broken, GO BACK to step donot allow inertia to become the constraint!From presentation by Steve CookIPPD 3/14/00 critical chain Typical Project Management 50,000 level schedule Resources are given due dates, not taskdurations No buffer, later tasks are forced to make upany slide Local optimization Management attention on all tasks Resources not de-conflicted Judge resources on whether they completedby due date and quality of workFrom presentation by Steve CookIPPD 3/14/00 critical ChainThe Process is the ProblemThe majority of all development projects fail tomeet their time and cost targets.

4 With theoverrun typically between 40 and :Dr. Edward B. Roberts, Strategic Managementof Technology:Global Benchmarking,December 10, 1992 The system you currently have is designed to giveyou the results you are getting now. J. CovingtonFrom presentation by Steve CookIPPD 3/14/00 critical ChainCritical chain The goal of critical chain is to help projects finish ontime, within budget, and without cutting scope. Main points- Cultural change in how to manage projects andevaluate team members Avoid multi-tasking while on the critical chain Protect against uncertainty by aggregating allsafety time at the end of the project Concentrate on the constraint of the project.

5 Thelongest chain of dependent tasks or resourcesFrom presentation by Steve CookIPPD 3/14/00 critical ChainProbability of Task Duration TimeTask Duration# of Outcomes Pure Success basis-not likely to repeatAVery likely you can meet thistime, even with some of the outcomes are less thanthis, 50% are greater. This is the estimate CC builds into the scheduleBEven with a majordisaster this timeis highly achievable, this is the time commonlyusedCWhich Time Are You Likely toPromise?From presentation by Steve CookIPPD 3/14/00 critical ChainTask Scheduled,Available Start DateTask ScheduledCompletion DateXMurphyEffortLevelTime Avraham Y.

6 Goldratt InstituteThe Student Syndrome From presentation by Steve CookIPPD 3/14/00 critical ChainTask XProject 1 One WeekTask YProject 2 One WeekTask ZProject 3 One WeekIn order to keep each project on track, aresource does half of task X, then half of task Y,then half of task Z, then finishes task X then Y,then long does each task take to complete?What happened to the safety time?1/2 X1/2 Y1/2 Z1/2 XHow Long?1/2 Y1/2 Z Avraham Y. Goldratt InstituteThe Multiplying Effect of Multi-taskingFrom presentation by Steve CookIPPD 3/14/00 critical ChainTask 15 DaysTask 25 DaysTask 35 DaysTask 410 DaysMerging paths don't allow us tobenefit from tasks completedearly.

7 What's the impact on the totalproject if Task 1 is done in only3 days? What if Task 3 takes 8 days? What if Tasks 1, 2, and 3,through some miracle, all getdone in 2 days? (Will Task 4 beready to start 3 days early?) Avraham Y. Goldratt InstituteDelays Are Passed on Gains Are NotFrom presentation by Steve CookIPPD 3/14/00 critical ChainA20B10C14E20D16B16 Resource E 20 day taskA10B5C7E10 Project Buffer 32D8B8 FeedingBuffer 1620 day task is cutto 10 daysSafety is aggregated at the end of the project to protect the completion date Feeding buffers are used to protect the longest pathTotal Schedule:64 days Avraham Y.

8 Goldratt InstituteGeneral critical chain ApproachFrom presentation by Steve CookIPPD 3/14/00 critical ChainA10 B5 C7E10 Project Buffer 32D8B8 FeedingBuffer 16A10B5C7D8B8FB 8E10 Project Buffer16 Because of aggregation theory thevariance is lower and lessprotection is necessaryTotal Schedule:48 days Avraham Y. Goldratt InstituteThe Aggregated Buffers Can BeSmaller Than the Sum of the IndividualSafetyFrom presentation by Steve CookIPPD 3/14/00 critical ChainCreate the initial planEInt dsgnP:Basic FunctionT:Build :Build :External DesignPE:IntegrationPE:self-testT:ASMP:A cceptancePE:Integration 2PE:Final TestFrom presentation by Steve CookIPPD 3/14/00 critical ChainCheck for resource conflictsEInt dsgnP:Basic FunctionT:Build :Build :External DesignPE:IntegrationPE:self-testT:ASMP:A cceptancePE:Integration 2PE:Final TestEInt dsgnP:Basic FunctionT:Build.

9 Build :External DesignPE:IntegrationPE:self-testT:ASMP:A cceptancePE:Integration 2PE:Final TestPE:Final TestPE:Integration 2PE:self-testPE:IntegrationE:P:T:IPPD 3/14/00 critical ChainLevel ResourcesEInt dsgnT:Build :Build :External DesignPE:IntegrationT:ASMP:AcceptancePE: Integration 2PE:Final TestEInt dsgnP:Basic FunctionT:Build :Build :External DesignPE:IntegrationP:self-testT:ASMPE:I ntegration 2PE:Final TestPE:Final TestPE:Integration 2PE:IntegrationE:P:T:P:AcceptanceP:Basic FunctionP:self-testIPPD 3/14/00 critical ChainNotes about leveling resources There is no one solution There are many algorithms to do this Very important in critical chain not to just putpeople on who approve or have presentation by Steve CookIPPD 3/14/00 critical ChainIdentify critical ChainEInt dsgnT:Build :Build :External DesignPE:IntegrationT:ASMP:AcceptancePE: Integration 2PE:Final TestEInt dsgnP:Basic FunctionT:Build :Build :External DesignPE:IntegrationP:self-testT:ASMPE:I ntegration 2PE:Final TestPE:Final TestPE:Integration 2PE:IntegrationE:P:T:P.

10 AcceptanceP:Basic FunctionP:self-testFrom presentation by Steve CookIPPD 3/14/00 critical chain The longest chain of dependant resources Time PeopleA10B5C7D8B8E10 Project Buffer 19FB5 Resource A completinga 10 day taskResource B must be deconflictedTotal Schedule:57 days Avraham Y. Goldratt InstituteWhat Is the Constraint of the Project?From presentation by Steve CookIPPD 3/14/00 critical ChainAdd buffersEInt dsgnT:Build :Build :External DesignPE:IntegrationT:ASMP:AcceptancePE: Integration 2PE:Final TestEInt dsgnP:Basic FunctionT:Build :Build :External DesignPE:IntegrationP:self-testT:ASMPE:I ntegration 2PE:Final TestPE:Final TestPE:Integration 2PE:IntegrationP:AcceptanceP:Basic FunctionP:self-testFrom presentation by Steve CookIPPD 3/14/00 critical ChainInsert resource readiness alerts (calledresource buffers)EInt dsgnT:Build :Build :External DesignPE:IntegrationT:ASMP.