The Critical Chain Method (CCM) is one of the methods used to perform Schedule Network Analysis that takes into account task dependencies, limited resource availability, and buffers. It’s used to prepare the project schedule when limited or restricted resources are available.
In this method, the Program Manager (PM) usually schedules all or most of the high-risk or critical activities in the earlier stage of the project schedule. This allows the critical tasks to be completed early as well as gives buffers to handle unexpected problems if arise. Also, the PM will combine several tasks into one task and assign one resource to handle all.
Critical Chain Method (CCM) Goal
The goal of the Critical Chain Method (CCM) is to eliminate project schedule delays due to uncertainties, overestimation of task duration, and wasted internal buffers.
Critical Chain Method (CCM) Steps
The six (6) steps involved in the CCM are:
- Identify all activities and dependencies
- Construct a Schedule Network Diagram
- Define constraints
- Determine critical path
- Determine buffers
- Apply resource availability
Critical Chain Method (CCM) Buffers
The CCM has three (3) different types of Buffers which are:
- Resource buffer: is inserted just before a critical chain activity where a critical resource is required. It’s used to remind the project team that a resource is needed and to finish up prior activities.
- Feeding buffer: is inserted as a safety margin in the non-critical chain of a network schedule. It’s placed where the path feeds back into the critical chain path.
- Project buffer: the summation of all the internal buffers added to each project task or activity.
Difference Between Critical Chain Method (CCM) and Critical Path Method (CPM)
There are few differences between the critical chain method and the critical path method but they both focus on schedule development and estimation. These are:
- Critical Path Method is focused on how long a project is based upon task estimation and the amount of float on a project.
- Critical Chain Method operates on shortening how long a project is due to overestimation, uncertainties, and buffers.
AcqLinks and References:
-  Defense System Management College “Scheduling Guide for Program Managers” – Oct 2001
- DoD “Integrated Master Plan and Integrated Master Schedule Preparation and User Guide” – 21 Oct 2005
- CDC “Project Scheduling Best Practices/Guide” – 30 Jun 2007
- GAO 12-120G “Schedule Assessment Guide: Best Practices for Project Schedule” – May 2012