TOC (Theory of Constraints) - Revision history

S213827 at 18:46, 15 March 2022

2022-03-15T18:46:56Z

S213827: /* Application */

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Application

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	=Application=		=Application=
	==From Manufacturing with DBR...==		===From Manufacturing with DBR...===
	One of the main methodology developed around Goldratt’s novel is the Drum-Buffer-Rope (DBR) approach. It was developed for manufacturing project and is used during the « Exploit » and « Subordinate » focusing steps from the previous section. DBR is a production scheduling methodology that controls the release of jobs from the system according to the constraint capacity.		One of the main methodology developed around Goldratt’s novel is the Drum-Buffer-Rope (DBR) approach. It was developed for manufacturing project and is used during the « Exploit » and « Subordinate » focusing steps from the previous section. DBR is a production scheduling methodology that controls the release of jobs from the system according to the constraint capacity.
	The three different components of DBR are the following <ref>Guide VDR. Scheduling using drum-buffer-rope in a remanufacturing environment. International Journal of Production Research. 1996;34(4):1081. doi:10.1080/00207549608904951		The three different components of DBR are the following <ref>Guide VDR. Scheduling using drum-buffer-rope in a remanufacturing environment. International Journal of Production Research. 1996;34(4):1081. doi:10.1080/00207549608904951
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	<div style="text-align: left">		<div style="text-align: left">

	==...to Project Management with CCPM...==		===...to Project Management with CCPM...===
	In project management, the critical path is the longest sequence of tasks that must be completed to complete a project. The tasks on the critical path are called critical activities because if they're delayed, the whole project completion will be delayed.		In project management, the critical path is the longest sequence of tasks that must be completed to complete a project. The tasks on the critical path are called critical activities because if they're delayed, the whole project completion will be delayed.

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	<div style="text-align: left">		<div style="text-align: left">

	==...to the the Thinking Processes.==		===...to the the Thinking Processes.===
	TOC has evolved through the years, from a manufacturing management method, it has become a methodology now regarded as a systems methodology applicable in any type of project. Through its tools for convergent thinking and synthesis, the Thinking processes (TP), which underpin the entire TOC methodology, help identify and manage constraints and guide continuous improvement and change in organizations. <ref> Kim, Seonmin, Victoria Jane Mabin, and John Davies. "The theory of constraints thinking processes: retrospect and prospect." International Journal of Operations & Production Management 28.2 (2008): 155-184. </ref>		TOC has evolved through the years, from a manufacturing management method, it has become a methodology now regarded as a systems methodology applicable in any type of project. Through its tools for convergent thinking and synthesis, the Thinking processes (TP), which underpin the entire TOC methodology, help identify and manage constraints and guide continuous improvement and change in organizations. <ref> Kim, Seonmin, Victoria Jane Mabin, and John Davies. "The theory of constraints thinking processes: retrospect and prospect." International Journal of Operations & Production Management 28.2 (2008): 155-184. </ref>
	Originally conceptualized by Goldratt, the TOC thinking processes approach to the management of change involves answering three basic questions:		Originally conceptualized by Goldratt, the TOC thinking processes approach to the management of change involves answering three basic questions:
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	Thinking processes are then a set of tools designed to help managers to go through the steps of initiating and implementing a project in a logical flow.		Thinking processes are then a set of tools designed to help managers to go through the steps of initiating and implementing a project in a logical flow.


	=Limitations=		=Limitations=

S213827: /* The Theory of Constraints */

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The Theory of Constraints

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	=The Theory of Constraints=		=The Theory of Constraints=
	==The Goal==		===The Goal===
	"The Goal : A process of ongoing improvement" <ref> Goldratt, Eliyahu M.; Cox, Jeff (1984). The Goal. Gower Publishing. ISBN 978-0-566-02683-6. </ref> is a novel by Eliyahu M. Goldratt and Jeff Cox published for the first time in 1984. This novel is focused on manufacturing and is halfway between a fiction and a case study.		"The Goal : A process of ongoing improvement" <ref> Goldratt, Eliyahu M.; Cox, Jeff (1984). The Goal. Gower Publishing. ISBN 978-0-566-02683-6. </ref> is a novel by Eliyahu M. Goldratt and Jeff Cox published for the first time in 1984. This novel is focused on manufacturing and is halfway between a fiction and a case study.

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	Finally, many re-editions of this novel has been edited by Eliyahu M. Goldratt and other contributors to dive deeper in the different approaches and methods of ongoing improvement implemented in the novel. The Theory of Constraint (TOC) is born from it and a wide set of tools related to it have been developed.		Finally, many re-editions of this novel has been edited by Eliyahu M. Goldratt and other contributors to dive deeper in the different approaches and methods of ongoing improvement implemented in the novel. The Theory of Constraint (TOC) is born from it and a wide set of tools related to it have been developed.

	==What is a Constraint==		===What is a Constraint===


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	The constraint is the limiting factor that is preventing the organization from getting more throughput. If its capacity is improved so it is no longer the system's limiting factor, it is said to "break" the constraint. The limiting factor is now some other part of the system, or may be external to the system.		The constraint is the limiting factor that is preventing the organization from getting more throughput. If its capacity is improved so it is no longer the system's limiting factor, it is said to "break" the constraint. The limiting factor is now some other part of the system, or may be external to the system.

	==The 5 Focusing Steps==		===The 5 Focusing Steps===

	Considering the TOC philosophy, performance improvement efforts are focused on the system’s constraints and is referred as « process of ongoing improvement ».		Considering the TOC philosophy, performance improvement efforts are focused on the system’s constraints and is referred as « process of ongoing improvement ».

S213827: /* Limitations */

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Limitations

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	=Limitations=		=Limitations=
	==TOC complexity==		===TOC complexity===

	One of the first limitation of the TOC is brought by Husby (2007) in his analyse of both Six Sigma and TOC approaches. Indeed, he relates that « the unique language and thinking process of TOC aren’t easy to master, and that can create a barrier to effective use across the enterprise. The problem-solving process uses an “intellectual” language requiring well trained experts for effective application. TOC’s process and language complexity, along with its top-down nature, aren’t conducive to engaging all team members." <ref> Husby, P. (2007). Competition or Complement: Six Sigma and TOC. Material Handling Management, 62(10), 51–55. </ref>		One of the first limitation of the TOC is brought by Husby (2007) in his analyse of both Six Sigma and TOC approaches. Indeed, he relates that « the unique language and thinking process of TOC aren’t easy to master, and that can create a barrier to effective use across the enterprise. The problem-solving process uses an “intellectual” language requiring well trained experts for effective application. TOC’s process and language complexity, along with its top-down nature, aren’t conducive to engaging all team members." <ref> Husby, P. (2007). Competition or Complement: Six Sigma and TOC. Material Handling Management, 62(10), 51–55. </ref>

	==The theory status==		===The theory status===

	On the other hand Spearman dives more deeply in the theory and raises some criticism against TOC.		On the other hand Spearman dives more deeply in the theory and raises some criticism against TOC.
	The first one is that the theory is not complete. Indeed, according to him: « Despite what its advocates imply, the TOC does not offer a complete management paradigm. There are times when trade-offs must be made and the TOC is hard pressed to provide much assistance in these situations ». <ref> Spearman, M., 1997. On the theory of constraints and the goal system. Production and Operations Management, 6 (1), 28–33. </ref>		The first one is that the theory is not complete. Indeed, according to him: « Despite what its advocates imply, the TOC does not offer a complete management paradigm. There are times when trade-offs must be made and the TOC is hard pressed to provide much assistance in these situations ». <ref> Spearman, M., 1997. On the theory of constraints and the goal system. Production and Operations Management, 6 (1), 28–33. </ref>

	==Time estimation in CCPM==		===Time estimation in CCPM===

	Estimations are guesses that usually include large safety margins. When planning CCPM and revising the tasks' durations, Goldratt estimates that they should be approximately be divided by two. However, there is no theory to support this number. In order to provide meaningful estimations, Program Evaluation and Review Technique (PERT) might be a method to revise and set concrete and realistic task duration.		Estimations are guesses that usually include large safety margins. When planning CCPM and revising the tasks' durations, Goldratt estimates that they should be approximately be divided by two. However, there is no theory to support this number. In order to provide meaningful estimations, Program Evaluation and Review Technique (PERT) might be a method to revise and set concrete and realistic task duration.

	==Risk vs Constraint==		===Risk vs Constraint===

	Unlike risks, constraints don't have a probability to occur. Constraints are certain to occur as they have been identified in the process. Thus, constraints management as presented with these different tools provided by TOC differs from risk management theory and methods that are commonly used in project and program management. It is then important not to take risks for constraints and vice versa as the tools for managing those are different.		Unlike risks, constraints don't have a probability to occur. Constraints are certain to occur as they have been identified in the process. Thus, constraints management as presented with these different tools provided by TOC differs from risk management theory and methods that are commonly used in project and program management. It is then important not to take risks for constraints and vice versa as the tools for managing those are different.

S213827: /* ...to Project Management with CCPM... */

2022-03-15T18:30:32Z

...to Project Management with CCPM...

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	Critical Chain Project Management (CCPM) is based on methods and algorithms derived from Theory of Constraints. Eliyahu M. Goldratt extended his TOC’s application to project management with CCPM <ref> Goldratt, E. M. (1997). Critical chain (pp. 246 s.). The North River Press, </ref>. The idea of CCPM was introduced in 1997 in his book, Critical Chain. Having researched reasons for project failure, Goldratt identified the main ‘constraint’ to project success as the ‘sequence of dependent events that prevents the project from being completed in a shorter interval’.		Critical Chain Project Management (CCPM) is based on methods and algorithms derived from Theory of Constraints. Eliyahu M. Goldratt extended his TOC’s application to project management with CCPM <ref> Goldratt, E. M. (1997). Critical chain (pp. 246 s.). The North River Press, </ref>. The idea of CCPM was introduced in 1997 in his book, Critical Chain. Having researched reasons for project failure, Goldratt identified the main ‘constraint’ to project success as the ‘sequence of dependent events that prevents the project from being completed in a shorter interval’.

	The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 2). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.		The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 3). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.

	[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure 3: '''Critical Path VS Critical Chain,''' Source: shortpixel.com]]		[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure 3: '''Critical Path VS Critical Chain,''' Source: shortpixel.com]]
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	To establish the critical chain methodology, activities from both the critical chain and non-critical chains are listed together with their logical dependencies and an estimate of their duration <ref> (2014). Critical Chain Project Management. In A Handbook for Construction Planning and Scheduling (eds A. Baldwin and D. Bordoli). https://doi-org.proxy.findit.cvt.dk/10.1002/9781118838167.ch5 </ref>.		To establish the critical chain methodology, activities from both the critical chain and non-critical chains are listed together with their logical dependencies and an estimate of their duration <ref> (2014). Critical Chain Project Management. In A Handbook for Construction Planning and Scheduling (eds A. Baldwin and D. Bordoli). https://doi-org.proxy.findit.cvt.dk/10.1002/9781118838167.ch5 </ref>.

	Feeding buffers (See Figure 3) are added to a non-critical chain so that any delays on a non-critical chain don’t affect the critical chain. They are inserted between the last task on a non-critical chain and the critical chain.		Feeding buffers (See Figure 4) are added to a non-critical chain so that any delays on a non-critical chain don’t affect the critical chain. They are inserted between the last task on a non-critical chain and the critical chain.
	The total time for the critical path is then reviewed from the perspective of the resource requirements of the activities. Resource buffers are set on the critical chain to ensure appropriate resources (people, equipment) are available throughout the project when needed. These resources are commonly known as critical resources.		The total time for the critical path is then reviewed from the perspective of the resource requirements of the activities. Resource buffers are set on the critical chain to ensure appropriate resources (people, equipment) are available throughout the project when needed. These resources are commonly known as critical resources.

S213827: /* From Manufacturing with DBR... */

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From Manufacturing with DBR...

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	One of the main methodology developed around Goldratt’s novel is the Drum-Buffer-Rope (DBR) approach. It was developed for manufacturing project and is used during the « Exploit » and « Subordinate » focusing steps from the previous section. DBR is a production scheduling methodology that controls the release of jobs from the system according to the constraint capacity.		One of the main methodology developed around Goldratt’s novel is the Drum-Buffer-Rope (DBR) approach. It was developed for manufacturing project and is used during the « Exploit » and « Subordinate » focusing steps from the previous section. DBR is a production scheduling methodology that controls the release of jobs from the system according to the constraint capacity.
	The three different components of DBR are the following <ref>Guide VDR. Scheduling using drum-buffer-rope in a remanufacturing environment. International Journal of Production Research. 1996;34(4):1081. doi:10.1080/00207549608904951		The three different components of DBR are the following <ref>Guide VDR. Scheduling using drum-buffer-rope in a remanufacturing environment. International Journal of Production Research. 1996;34(4):1081. doi:10.1080/00207549608904951
	</ref>:		</ref> (See Figure 2):

	• The Drum is the exploitation of a constraint, includes detailed schedule. Since the constraint is limiting the performance, it gives the pace of the production as drums do.		• The Drum is the exploitation of a constraint, includes detailed schedule. Since the constraint is limiting the performance, it gives the pace of the production as drums do.

S213827: /* ...to Project Management with CCPM... */

2022-03-15T18:28:57Z

...to Project Management with CCPM...

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	The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 2). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.		The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 2). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.

	[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure ~~2.2~~: ''Critical Path VS Critical Chain,'' Source: shortpixel.com]]		[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure 3: '''Critical Path VS Critical Chain,''' Source: shortpixel.com]]
	<div style="text-align: left">		<div style="text-align: left">

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	By doing so, task owners are only focused on completing the task properly in the right time. There is no lost time in between the activities. The project still protects the chain from being completed in time but it is more likely to be completed in less time than would have been the critical path <ref name="shou"/>.		By doing so, task owners are only focused on completing the task properly in the right time. There is no lost time in between the activities. The project still protects the chain from being completed in time but it is more likely to be completed in less time than would have been the critical path <ref name="shou"/>.

	[[File:tonpere.png\|center\|700px\|thumb\|<div style="text-align: center">Figure ~~2.2~~: ''Critical Chain Project Management, '' Source: activecollab.com]]		[[File:tonpere.png\|center\|700px\|thumb\|<div style="text-align: center">Figure 4: '''Critical Chain Project Management, ''' Source: activecollab.com]]
	<div style="text-align: left">		<div style="text-align: left">

S213827: /* From Manufacturing with DBR... */

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From Manufacturing with DBR...

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	Three steps are required to schedule DBR <ref> Schragenheim, E., & Ronen, B., 1990, Drum-buffer-rope shop floor control, Production and Inventory Management Journal, 31(3), 18-23 </ref>. The first one is to schedule the constraint and exploit it according to the objectives. The second is to determine the buffer sizes and the final one is to derive the materials release schedule according to the two previous steps.		Three steps are required to schedule DBR <ref> Schragenheim, E., & Ronen, B., 1990, Drum-buffer-rope shop floor control, Production and Inventory Management Journal, 31(3), 18-23 </ref>. The first one is to schedule the constraint and exploit it according to the objectives. The second is to determine the buffer sizes and the final one is to derive the materials release schedule according to the two previous steps.

	[[File:DBR.jpeg\|center\|600px\|thumb\|<div style="text-align: center">Figure 1.2: ''Drum-Buffer-Rope Diagram.'' Source: planettogether.com]]		[[File:DBR.jpeg\|center\|600px\|thumb\|<div style="text-align: center">Figure 2: '''Drum-Buffer-Rope Diagram.''' Source: planettogether.com]]

	<div style="text-align: left">		<div style="text-align: left">

S213827: /* The 5 Focusing Steps */

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The 5 Focusing Steps

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	• If the constraint is broken, return to the first step. Once capacity is added to the existing constraint, the constraint might be broken. It implies that there is a new constraint whether it is in the system (internal) or not (external). New rules will be applied to deal with this one as non-constraints are also different. This step closes the loop of the five focusing steps and allows to get in an ongoing process of improvement.		• If the constraint is broken, return to the first step. Once capacity is added to the existing constraint, the constraint might be broken. It implies that there is a new constraint whether it is in the system (internal) or not (external). New rules will be applied to deal with this one as non-constraints are also different. This step closes the loop of the five focusing steps and allows to get in an ongoing process of improvement.

	[[File:focusingsteps.jpeg\|center\|250px\|thumb\|<div style="text-align: center">Figure 1.6: ''The Five Focusing Steps.'' Source:smartsheet.com]]		[[File:focusingsteps.jpeg\|center\|250px\|thumb\|<div style="text-align: center">Figure 1: '''The Five Focusing Steps.''' Source:smartsheet.com]]
	<div style="text-align: left">		<div style="text-align: left">

S213827: /* ...to Project Management with CCPM... */

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...to Project Management with CCPM...

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	The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 2). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.		The critical chain approach differs from the critical path approach where the critical path is defined as the longest sequence of tasks that must be completed to complete the project (See Figure 2). Goldratt argues that safety time and its use is of crucial importance in project management. Critical path is criticized to deal with uncertainty in the same way for all activities, whether or not they are on the critical path. Unlike the critical path where safety time is added at the end of each activity, the critical chain aggregates these safety times at the end of the chain as a project buffer. Activities then start at the latest and the project buffer ensures that the chain’s schedule is respected.

	[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure 2.2: ''Critical Path VS Critical Chain'']]		[[File:cpvscc.jpeg\|center\|700px\|thumb\|<div style="text-align: center">Figure 2.2: ''Critical Path VS Critical Chain,'' Source: shortpixel.com]]
	<div style="text-align: left">		<div style="text-align: left">

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	By doing so, task owners are only focused on completing the task properly in the right time. There is no lost time in between the activities. The project still protects the chain from being completed in time but it is more likely to be completed in less time than would have been the critical path <ref name="shou"/>.		By doing so, task owners are only focused on completing the task properly in the right time. There is no lost time in between the activities. The project still protects the chain from being completed in time but it is more likely to be completed in less time than would have been the critical path <ref name="shou"/>.

	[[File:tonpere.png\|center\|700px\|thumb\|<div style="text-align: center">Figure 2.2: ''Critical Chain Project Management'']]		[[File:tonpere.png\|center\|700px\|thumb\|<div style="text-align: center">Figure 2.2: ''Critical Chain Project Management, '' Source: activecollab.com]]
	<div style="text-align: left">		<div style="text-align: left">

← Older revision		Revision as of 18:46, 15 March 2022
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	The Theory of Constraints (TOC) was introduced in 1984 by Dr. Eliyahu Goldratt in his bestselling novel « The Goal ». It has been developed continuously since then by Dr. Goldratt as well as other contributors and has become a notable method in the world of management.		The Theory of Constraints (TOC) was introduced in 1984 by Dr. Eliyahu Goldratt in his bestselling novel « The Goal ». It has been developed continuously since then by Dr. Goldratt as well as other contributors and has become a notable method in the world of management.
	<br>This theory is a problem-solving management method. TOC is based on an iterative method for improvement. It considers every system as a chain of activities that operates one after another and hypothesizes that this chain is not stronger than its weakest link. Indeed, among these activities, one acts as a constraint upon the entire system, i.e. the weakest link. These limiting factors or constraints, also referred as bottlenecks, are slowing down the process of a system.		<br>This theory is a problem-solving management method. TOC is based on an iterative method for improvement. It considers every system as a chain of activities that operates one after another and hypothesizes that this chain is not stronger than its weakest link. Indeed, among these activities, one acts as a constraint upon the entire system, i.e. the weakest link. These limiting factors or constraints, also referred as bottlenecks, are slowing down the process of a system.
	<br>The overall goal is to eliminate these constraints in order to enhance performance. To do so, five steps have been defined as the key steps of all the methods derived from TOC. These Five Focusing Steps are : Identify, Exploit, Subordinate, Elevate and Warning.
			<br>The overall goal is to eliminate these constraints in order to enhance performance. To do so, five steps have been defined
			as the key steps of all the methods derived from TOC. These Five Focusing Steps are : Identify, Exploit, Subordinate, Elevate and Warning.

	The first application of TOC was for manufacturing but it has evolved and is now applicable for any type of project management. Indeed,		The first application of TOC was for manufacturing but it has evolved and is now applicable for any type of project management. Indeed,
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	The five focusing steps are:		The five focusing steps are:

	• Identify the system’s constraint(s): whether they are external, equipment, people or policy constraints. Since constraints are limiting the global performance, it is the first step to achieve improvement.		:: • Identify the system’s constraint(s): whether they are external, equipment, people or policy constraints. Since constraints are limiting the global performance, it is the first step to achieve improvement.

	• Decide how to exploit the system’s constraint(s). The objective here is to make the constraint as effective as possible with what is currently available. This step is mostly used when dealing with physical constraints.		:: • Decide how to exploit the system’s constraint(s). The objective here is to make the constraint as effective as possible with what is currently available. This step is mostly used when dealing with physical constraints.

	• Subordinate everything else to the decisions made in step two. Everything else is all the non-constraints, i.e. activities that have more capacity than the actual constraint. The point of subordinating every other decisions is that any decision on non-constraints will generate necessary extra work load that the constraint can currently not deal with. Indeed the capacity of the system is limited by the constraint, not by the non-constraints Thus the priority is the take action on the constraint first.		:: • Subordinate everything else to the decisions made in step two. Everything else is all the non-constraints, i.e. activities that have more capacity than the actual constraint. The point of subordinating every other decisions is that any decision on non-constraints will generate necessary extra work load that the constraint can currently not deal with. Indeed the capacity of the system is limited by the constraint, not by the non-constraints Thus the priority is the take action on the constraint first.

	• Elevate the system’s constraint(s). If the improvement is no longer possible with the two previous steps, the next step is to put extra efforts on the constraints and elevate its capacity. Extra efforts to enhance capacity require investment and require time. As the performance improves, to potential of non-constraint can be exploited and it it will increase the overall system performances.		:: • Elevate the system’s constraint(s). If the improvement is no longer possible with the two previous steps, the next step is to put extra efforts on the constraints and elevate its capacity. Extra efforts to enhance capacity require investment and require time. As the performance improves, to potential of non-constraint can be exploited and it it will increase the overall system performances.

	• If the constraint is broken, return to the first step. Once capacity is added to the existing constraint, the constraint might be broken. It implies that there is a new constraint whether it is in the system (internal) or not (external). New rules will be applied to deal with this one as non-constraints are also different. This step closes the loop of the five focusing steps and allows to get in an ongoing process of improvement.		:: • If the constraint is broken, return to the first step. Once capacity is added to the existing constraint, the constraint might be broken. It implies that there is a new constraint whether it is in the system (internal) or not (external). New rules will be applied to deal with this one as non-constraints are also different. This step closes the loop of the five focusing steps and allows to get in an ongoing process of improvement.

	[[File:focusingsteps.jpeg\|center\|250px\|thumb\|<div style="text-align: center">Figure 1: '''The Five Focusing Steps.''' Source:smartsheet.com]]		[[File:focusingsteps.jpeg\|center\|250px\|thumb\|<div style="text-align: center">Figure 1: '''The Five Focusing Steps.''' Source:smartsheet.com]]
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	</ref> (See Figure 2):		</ref> (See Figure 2):

	• The Drum is the exploitation of a constraint, includes detailed schedule. Since the constraint is limiting the performance, it gives the pace of the production as drums do.		:: • The Drum is the exploitation of a constraint, includes detailed schedule. Since the constraint is limiting the performance, it gives the pace of the production as drums do.

	• The Buffer is the protection time that prevents the system from eventual disruptions as absenteeism, raw material delivery delay or other breakdowns at non-constraint level. Buffers are measured in time units. They reflects the capacity level of non-constraint resources and determines the time needed to for these latter to catchup in case of disruption. The use of time buffers to improve throughput is often referred as buffer management.		:: • The Buffer is the protection time that prevents the system from eventual disruptions as absenteeism, raw material delivery delay or other breakdowns at non-constraint level. Buffers are measured in time units. They reflects the capacity level of non-constraint resources and determines the time needed to for these latter to catchup in case of disruption. The use of time buffers to improve throughput is often referred as buffer management.

	•Rope is a communication mechanism between critical control points that will force the different parts to synchronize at the pace of the drum. Based on the feedback provided, order release aligns the input of work with the output rate of the constraint. A maximum limit on the number of jobs released to the bottleneck but not yet completed is established and a job is released whenever the number of jobs is below the limit		:: •Rope is a communication mechanism between critical control points that will force the different parts to synchronize at the pace of the drum. Based on the feedback provided, order release aligns the input of work with the output rate of the constraint. A maximum limit on the number of jobs released to the bottleneck but not yet completed is established and a job is released whenever the number of jobs is below the limit

	Three steps are required to schedule DBR <ref> Schragenheim, E., & Ronen, B., 1990, Drum-buffer-rope shop floor control, Production and Inventory Management Journal, 31(3), 18-23 </ref>. The first one is to schedule the constraint and exploit it according to the objectives. The second is to determine the buffer sizes and the final one is to derive the materials release schedule according to the two previous steps.		Three steps are required to schedule DBR <ref> Schragenheim, E., & Ronen, B., 1990, Drum-buffer-rope shop floor control, Production and Inventory Management Journal, 31(3), 18-23 </ref>. The first one is to schedule the constraint and exploit it according to the objectives. The second is to determine the buffer sizes and the final one is to derive the materials release schedule according to the two previous steps.
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	The five tools or logic diagrams are <ref> Scoggin, J. M., Segelhorst, R. J., & Reid, R. A. (2003). Applying the TOC thinking process in manufacturing: A case study. International Journal of Production Research, 41(4), 767–797. https://doi.org/10.1080/0020754031000065557 </ref>:		The five tools or logic diagrams are <ref> Scoggin, J. M., Segelhorst, R. J., & Reid, R. A. (2003). Applying the TOC thinking process in manufacturing: A case study. International Journal of Production Research, 41(4), 767–797. https://doi.org/10.1080/0020754031000065557 </ref>:

	•Current reality tree (CRT): designed to help identify the system constraint responsible for a majority of undesirable effects (UDE’s). It is a particularly effective tool if the constraint is a policy.		:: •Current reality tree (CRT): designed to help identify the system constraint responsible for a majority of undesirable effects (UDE’s). It is a particularly effective tool if the constraint is a policy.

	•Evaporating cloud (EC) (Kim): designed to address conflict or dilemma situations by diagramming the logic behind the conflict and methodically examining the assumptions behind the logic.		:: •Evaporating cloud (EC) (Kim): designed to address conflict or dilemma situations by diagramming the logic behind the conflict and methodically examining the assumptions behind the logic.

	•Future reality tree (FRT): designed to see how changes would affect current reality. Its primary purpose is to evaluate logically the effectiveness of new ideas or injections before they are actually implemented.		:: •Future reality tree (FRT): designed to see how changes would affect current reality. Its primary purpose is to evaluate logically the effectiveness of new ideas or injections before they are actually implemented.

	•Prerequisite tree (PRT): designed to describe the necessary condition relationships require to accomplish the desired objectives.		:: •Prerequisite tree (PRT): designed to describe the necessary condition relationships require to accomplish the desired objectives.

	•Transition tree (TT): designed to develop a detailed step-by-step set of actions that need to be completed in order to implement change within an organization.		:: •Transition tree (TT): designed to develop a detailed step-by-step set of actions that need to be completed in order to implement change within an organization.

	The ancillary tool is called a negative branch reservation (NBR) and is aimed at document ing potentially undesirable effects of change introduced in the FRT.		The ancillary tool is called a negative branch reservation (NBR) and is aimed at document ing potentially undesirable effects of change introduced in the FRT.