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Distinguish Critical Path Method from Critical Chain Method: - Critical Path Method Critical Chain Method Definition: - CPM is an algorithm for scheduling a set of project activities and commonly used in conjunction with the program evaluation and review technique. CPM has developed in the late 1950 by Morgan R Walker. CPM helps to identify critical and non-critical tasks from project’s start to end and helps in short-term prevention. The longest path is known as the critical path, and the duration of the critical path is the duration of the project. Definition: - CCM is based on methods and algorithms derived from Theory of Constraint. It was introduced in 1997 and it has been credited with achieving projects 10%-50% faster and cheaper than traditional methods. Advantages: - 1. Offers a Visual representation of the project activities 2. Provides time to complete the tasks and overall project. 3. Helps in tracking critical activities Advantages: - 1. Removes bottleneck to resolve constraints (Theory of Constraints) 2. Lean: Eliminate wastes & Six Sigma: Reduce Variation 3. Helps in Planning and control process Terms Used & Difference: - Float 1. Calculated Difference between the critical and non-critical path 2. Float is Zero. 3. Can't be used as tool to check Project status. 4. Activities - early start or late start, early finish or late finish possible. 5. Types - Free & Total floats Terms Used & Difference: - Buffer 1. Based on contingencies 2. Buffer is not Zero 3. Can be used to analyze Project status 4. Activities - only a start and an end 5. Types - Project, Feeding & Resource Buffer Method: - CPM is all about Managing activities 1. Resources will be provided whenever they are needed. 2. It’s not useful to gain time by completing an activity as next task can't be stared before its early start time. So you can't utilize the time by completing previous activity early. 3. Member will not start activity till its late start, and utilize the float if an activity has a float. Method: - CCM is all about Managing buffers 1. Consider Resources availability is limited and builds a realistic schedule based available resources. Provides more realistic and better schedule 2. Whenever an activity is completed, you can start the next activity and the time remains will be added as buffer. 3. Buffer is placed at the end of project and each task has its real time. How does Critical Chain method relate with Theory of Constraints or with Lean Management practices? CCM is an outgrowth of the Theory of Constraints to scheduling and managing manufacturing. 1. Theory of Constraints focuses on identifying and fixing bottlenecks to improve throughput and CCM focuses on bottlenecks. Example, Manufacturing Company was facing delay with new product approval. It was found that bottleneck was expert testing engineer to analyze more test results. And Expert testing engineer hiring cost is more than the revenue expected to launch the products to market sooner. 2. CCM is the realizing component to the theoretical TOC which typically has applied through five steps. 3. CCM and TOC both are concentrating more into the micro elements for a specific process. 4. CCM and TOC is more focused on the management of time, duration and uncertainty of Projects. 5. CCM and TOC can have distinguishing and remarkable outcomes for tasks completion and monitoring. 6. CCM focused on bottleneck similar like Lean management practices where Lean management talks about the improvement lean by eliminating the bottlenecks. Thanks to resource:- https://blog.pmsprout.com/critical-path-method-versus-critical-chain-method/ https://www.invensislearning.com/resources/pmp/critical-path-critical-chain-method http://apppm.man.dtu.dk/index.php/Critical_Chain_Theory https://www.ijser.org/researchpaper/A-Comparison-Between-Lean-Implementation-and-Critical-Chain-Management.pdf

Critical path method CPM is used for scheduling a set of project activities and it identifies the critical activities of a program or project. As a conclusion it results in finding shortest time to complete a project It emphasis more on task orders and scheduling CPM principle is simple sequencing approach it is not feasible in case of resource constrained scheduling CPM calculates only duration taken for each activity and it arises problem in case of activities that have been delayed. It will affect the entire cycle of project completion CPM helps to identify bottlenecks in the project. Since it is calculating Early start (ES), Early Finish (EF), Late start (LS) and Late finish (LF) through forward and backward passes from project schedule network diagram Critical chain method CCM is used for scheduling and managing a set of project activities only when limited or restricted resources are available. Here project manager will schedule most of the high risk or critical activities at the earlier stage itself. It has buffers to handle unexpected problems in middle It emphasis more on resource management involved in the project CCM principle is network based analysis and it is well suited for resource constrained scheduling CCM has prior knowledge about resource sharing activities and it has wide range of choice on activities that will be delayed to eliminate resource conflict. So it improves performance by avoiding activities which are all sharing resources will not be scheduled simultaneously CCM is fully relies on priority and resource dependent task mapped. This helps in project management team to identify each location potential based on their production CCM Relation with theory of constraints The critical chain method derived from “Theory of constraints” was originally developed by Eliyahu Goldratt. TOC focus on improving throughputs of overall system by identifying and fixing bottlenecks in the system. CCM deals with resource availability or uncertainties in the project. The traditional triple constraints of time, scope and cost still exist in CCM with add on project constraint. Critical tasks are separated from the tasks which have low priority and the next step is deploying resources to complete those critical tasks at first. Uncertainty Management 1. Average task duration estimation Reduces duration of activity estimation by 50% which gains excessive safety time. This is implemented strategically as buffers in project. 2. Resource constraint Resource contentions is removed by leveling the project plan. It also determines resource dependencies. 3. Including Buffers in project Plan Resource buffer- Protect critical chain by ensuring resource availability and when the critical resource availability is needed. Feeding buffer- protect critical chain from accumulation of negative variations by inserting safety margins in the non-critical chain paths of network schedule which again feeds back into the critical chain path. Project buffer- summation of all internal buffers included in the project. 4. Prevention of Multitasking Tasks does not contain any predecessor so it prevents from multitasking which helps to increase the speed of a resource while completing a task. 5. Buffer management Use buffer management to control the plan. This help manager to get regular information from buffer. Insist manager to take necessary recovery action at exact time.

Critical path and Critical chain method: Both Critical Path and Critical chain methods are types of schedule network diagramming techniques used in developing the project schedule. Critical path is the longest path of schedule network and the duration of critical path is the project duration. Floats are calculated, based on difference between critical and non critical pathway. Free float can be defined as the amount of time an activity can be delayed, without any delay in the successor activity. Total float can be defined as amount of delay in the activity that can be done, without affecting the overall project duration. Floats in all critical path activities are zero. Critical chain is modification of critical pathway with resource optimization. Based on resource availability schedule is prepared. Here buffers are used instead of float. Buffers account for contingency. Buffer is not zero in critical chain pathway. There is no early and late start or early and late finish. There can be only one start and one finish. The Project Buffer is the total buffer at the end of the project. Any delayed activity can consume this buffer. The Feeding Buffer is the buffer added to non critical chain , so that these non critical chain, if delayed, can use this buffer. The Resource Buffer is a resource kept as buffer along critical chain, so that continuity of the work is ensured. Differences Between Critical Path and Critical Chain Method Resources The critical path method does not assume any resource constraint and assumes that it is freely available. The critical chain method, on the contrary assumes resource constraint and builds a realistic schedule based on availability. Critical chain based method schedule may be of longer duration, but is more realistic. Float/Buffer In the critical path method, float can not be utilized before the early start of succeeding activity. While in case of critical chain, if preceding activity gets finished early, succeeding activity can be started earlier and time saved will be added to project buffer. Misuse of Float In the critical path method, team members often do not start an activity, until they utilize the float of the activity completely, till late start. Where as in critical chain, each activity has a realistic schedule and time gained is placed at the end of project as project buffer. Project progress: Floats can not be used to assess project progress, where as buffers can be used to analyze project progress. Critical path method: Critical Chain method: Correlation of Critical chain with lean and theory of constraints: Lean management aims at value creation over entire processes of organization, where as critical chain and theory of constraints are centered on managing time duration and uncertainties of the project. The uncertainties of durations and project completion can be contributed to inadequate management processes, which can be sorted by lean management practices. Lean practice implementation has greater effect on correcting processes unevenness, eliminating wastes and have more impact on whole organization, whereas critical chain and theory of constraint methods are efficacious in task completion on time and project monitoring, by optimizing the resource constraint. Images Sources: Critical Path: www.blog.pmsprout.com Critical Chain: www.blog.pmsprout.com