Critical Chain – Ch Key Takeaways Group 5 Regina Anderson Ken Fong Brent Hawkins Jianhua Zhang

Safety Lots of safety in typical estimates (at both the project and task levels) –Estimates usually given at 80% conf. levels –Equates to 200% margin of safety But why do tasks and project still overrun!?

Ways Safety Is Wasted The student syndrome –No rush to start, wait until the last minute –Leave just enough time (the ‘true’ estimate) –Consequence: No margin for errors, delays, or the unexpected Safety already spent during the initial start delay

Ways Safety Is Wasted Multitasking –Results in increased lead times

Ways Safety Is Wasted Dependencies –Causes delays to accumulate while wasting away the advances –Example: 4 dependent tasks, 3 finishes ahead (-5 days), 1 finishes behind (+15 days) Statistically, gainers average out the laggards In reality, the advances are lost, early finishes are rarely reported Results in a net delay of 15 days

Bottleneck / Early Start Dilemma Ex: soldiers in a line building a road –Lead time and WIP inventory interchangeable Represented by the distance between the soldiers –Differences in production rates cause soldiers to move at different paces, i.e. creates gaps  Soldiers will eventually spread out, with the largest gap at the bottleneck

Bottleneck / Early Start Dilemma Solutions –Chain them all together tightly, aka assembly line / conveyor belt method Throughput suffers, everyone moves at the pace of the slowest producer –Chain them together with some slack = J.I.T. Similar to conveyor belt example Introduces containers which allows for a limited input buffer to accumulate Creates additional inventory however

Bottleneck / Early Start Dilemna A better solution –Chain the leader to the bottleneck Leader moves at the pace of the bottleneck Length of chain from leader to bottleneck = buffer Eliminates need for excess buffers / WIP inventory –Keeps a buffer only at where it is needed, the bottleneck