Critical Chain
Category:Critical Chain.
Contents |
Abstract
Critical Chain Project Management(CCPM) was firstly introduced by Israeli physicist, Eliyahu M. Goldratt in his book “Critical Chain”. The development of CCPM was a response to poor time management in projects that the critical path method was not able to solve. One can therefore state that Critical Path is a precursor to Critical Chain.
Critical Chain
Time management in projects
Two problems often arises in relation to being on time in projects.
- People procrastinate and start on a task to finish the task just in time, also called "The student syndrome"
- Even if a worker finishes early they use all the time available, which can be explained by Parkinson's law. If one finishes early they will expand the scope and use more effort on the task than required.
Critical Chain acknowledges the need of safety margins in projects to reduce risks but safety margins will not prevent the project from being late due to the aforementioned problems.
Critical Path versus Critical Chain
Critical path schedules projects on task dependencies while Critical Chain is based on resources. Critical Chain does not prohibit concurrent project work but multitasking is prohibited meaning that work on one task cannot be interrupted to start another. Multitasking fails to complete tasks fast since the resource is split between multiple tasks and also due to the fact that there is a certain amount of communication time switching from one task to another.
With critical path the focus is on being as fast as possible in stead of meeting the task deadlines.
Critical Chain application
In order to apply Critical Chain the following steps need to be followed.
- Determine order of tasks and critical path: Identify the tasks needed to succeed with the project as well as their sequence. Determine critical path.
- Slice the duration of the tasks: Typically the PM will decide on half/half for simplicity but other slices are possible. Put the sliced task duration as a project buffer. The official end-date that is communicated to stakeholders now corresponds to the project buffer’s end date.
- Level resources: Identify resource constraints and arrange tasks according to resource dependencies. Determine critical chain.
- Monitor: During the project monitor the use of the use-rate of the buffer.
The different buffers
Buffers are owned by everyone and therefore a shared responsibility meaning that everyone must complete their task as quickly as possible to reduce the consumption of the buffers. The 'crashed' deadlines ensures that all resources will try to complete their task as quickly as possible with the safety of the buffers to ensure quality and a healthy work environment.
Some people divide the buffers in four categories: project buffers, feeding buffers, resource buffers and capacity buffers. The most well-known buffers are the project buffer and the feeding buffer:
- The project buffers: Placed between the last task and the official completion date ensuring the final date is not prolonged
- The feeding buffers: Placed at the end of non-critical chains preventing delays to the critical chain
Limitations
CCOM does not deal with project quality and by implementing tight deadlines there is a
