Manufacturing ERP Software


Categories: Theory of Constraints
Taking the Padding Out of Projects with CCPM

Taking the Padding Out of Projects with CCPM

By Bob Sproull


In my last post I explained how Critical Chain Project Management cuts the task duration times in half and then adds part of the removed times to a project buffer.  Having this project buffer allows one to withdraw time from the buffer when additional time is needed to complete a task.  By the same token, when a task is finished ahead of its scheduled time, time is added back into the project buffer.   In today’s post we will look into how CCPM eliminates the negative effects of the Student Syndrome and Parkinson’s Law.

Critical Chain Project Management

One of the key differences between CPM and CCPM is what happens at the task level.  In traditional project management (CPM) we said earlier that each task has a scheduled start and completion date.  CCPM eliminates the times and dates from the schedule and instead focuses on passing on tasks as soon as they are completed.  This function serves to eliminate the negative effects of both the Student Syndrome and Parkinson’s Law from the equation and permits on-time and early finishes for projects.  In order for this to work effectively, there must be a way to alert the next resource to get ready in time.  This is equivalent to a relay race where the baton is handed off from one runner to the next.

Earlier, we explained that in traditional project management we track the progress of the project by calculating the percentage of individual tasks completed and then comparing that percentage against the due date.  The problem with this method is because we aren’t considering the estimated durations that are left to complete, it is nearly impossible to know exactly how much time is remaining to complete the project.  Using this method to track progress, many times you’ll see 90 % of a project completed relatively quickly only to see the remaining 10 % take just as long. In fact, looking at the number or percentage of tasks completed instead of how much of the critical path has been completed only serves to give a false sense of conformance to the schedule. CCPM measures the progress of a project much differently and in so doing allows the project to make valuable use of early finishes.

Critical chain uses something called a Fever Chart which is simply a run chart of % of Critical Chain Complete versus % of Project Buffer consumed.  The figure below is an example of such a chart. In this chart we see that roughly 55 % of the critical chain has been completed while only 40 % of the project buffer has been consumed, thus indicating that this project is actually a bit ahead of schedule.

The green, yellow and red zones on the fever chart are visual indicators of how the project is progressing. If the data point falls within the green area of the chart, the project is progressing well and may even finish early. If the data point falls into the yellow zone, there is cause for concern and plans should be developed to take action, but not yet implemented. If a data point falls into the red zone, then the plan we developed should now be executed.


Next Time

In my next post we’llcomplete our discussion on CCPM and then discuss what kind of results you can expect when switching to it to manage your projects.  As always, if you have any questions or comments about any of my posts, leave me a message and I will respond. 

Until next time.

Bob Sproull

Bob Sproull

About the author

Bob Sproull has helped businesses across the manufacturing spectrum improve their operations for more than 40 years.

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