Improving Scheduling Using Critical Chain Project Management (CCPM)
On December 17, 2002, Shelby County Habitat of Humanity, a nonprofit ecumenical housing ministry, broke the world record for the fastest habitat house ever built in 3 hours, 26 minutes, and 34 seconds. Chad Calhoun, the project manager, attributed the project success to the careful planning of each activity, the readiness and organization of all the resources and materials, and the serious commitment to the sensitive schedule. The project kicked off at 11:00 AM on December 17th with the prefabricated wall panels already set in place and ready to be lifted. This was immediately followed by raising the interior panels which lasted exactly 16 minutes as planned. A series of tasks were later executed by dedicated workers and involved plumbing, wiring, carpeting, flooring, painting, and installation of lightnings, cabinets, electrical outlets, windows, and porches. The construction of the 14,000-pound roof was taking place simultaneously on the ground. Upon completion, it was lifted using a crane and attached accordingly. During that time, another crew of workers was busy handling interior work like decorations while others were planting shrubs in the yard. The house was completed around 2:21 PM.
The scenario above represents a typical example of a project where speed and completion time are essential conditions for its success. This kind of projects requires considerable training, management commitment, and a change in the working behavior of resources to be able to achieve the required benefits and outcomes. This constitutes a type of project management developed by Eliyahu M. Goldratt and was termed as Critical Chain Project Management (CCPM). Goldratt, the proponent of the Theory of Constraints, pinpointed how project managers tend to manage slack for their resource-limited projects. They either attempt to add slack at the end of the project and commit themselves to a completion date that is far beyond the scheduled date, or attempt to start their project early and refrain from using slacks of activities to ensure early completion.They also tend to overestimate or pad by providing activity time estimates that have 80 or 90 percent chance to be completed before that estimated time. All this would eventually help in finishing a project ahead of the planned schedule.
However in reality, even with all this over-estimation, many projects tend to finish behind schedule. Goldratt in his book Critical Chain attributes this to several reasons:
- Student Syndrome: As students procrastinate preparing for their exams until the last minute, workers also defer starting their tasks when they notice they have enough time to finish their tasks later. This puts task completion time at risk especially when emerging problems start showing up.
- Parkinson’s Law: Why rush into completing a task early when it is due until the day after tomorrow? Workers tend to delay outstanding work until the next day although they can finish it today. This unfortunately decreases productivity and slows down work. Yet workers instead can prevent this phenomenon by utilizing their free time to catch up with other work.
- Dropped Baton: The time gained from starting and completing an activity early could be wasted if the next group of workers who is responsible for receiving the output of the activity work is not ready. This could be due to lack of communication and coordination and improper resource scheduling. Goldratt compares this scenario to a relay race whereby the next runner is not ready to receive the baton from the first runner which eventually leads to a time loss.
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