Theory of Constraints
The Theory of Constraints is a methodology for identifying the most important factor limiting such duress that shows how to achieve a goal and to systematically improve this constraint until it is no longer the limiting factor in the production the stress is often called the neck.
The theory stresses a scientific approach to the improvement He hypothesizes that all complex systems, including manufacturing process consists of several activities, one that acts as a constraint on the whole system ie the stress activity is “weakest link in the chain”.
So what is the ultimate goal of most manufacturing companies to make a profit in the short term and long term †The Theory of Constraints provides a powerful set of tools to help achieve this goal, including.
The five stages of development of a methodology to identify and remove constraints.
The process of reflection and analysis tools for problem solving.
FLOW accounting method to measure performance and guide management decisions.
Dr. Eliyahu Goldratt developed the Theory of Constraints TOC, and introduced to a wide audience through his best-selling 1984 “The Goal” Since OCD continued to evolve and grow, and today it is an important factor in the world of best management practices.
One of the interesting features of the theory of constraints is that it gives priority inherently improvement activities The priority is always the current constraint In environments where there is an urgent need to improve, TOC provides a methodology highly targeted to the creation of a rapid improvement.
A successful theory of implementation constraints will have the following advantages.
Increased OCD target primary benefit to most businesses.
Fast improvement due to focus all attention on a critical area †stress the system.
Improved ability to optimize the constraint allows more products to be manufactured.
Reduction of time to optimize the stress results in the flow of smoother and faster products.
Reduce inventory eliminating bottlenecks means there will be less work in progress.
The basic concept of the theory of constraints is that each process has one constraint and that the total throughput of the process can be improved when the stress is improved An important corollary to this is that expenditures by optimizing non-constraints not provide significant benefits; that improving stress deepen the objective achieve more profit.
Thus, OCD seeks to provide accurate and sustained attention to the improvement of the current constraint until it no longer limits the flow, how the focus moves to the next constraint The underlying power of OCD flow its ability to generate a very strong attention towards the one goal of profit and eliminate the main obstacle to the realization of the stress over that goal actually focus Goldratt considers as the essence of the TOC.
The constraint theory provides a specific methodology for identifying and removing constraints, called the five stages of development As shown in the diagram below, it is a cyclic process.
The theory of constraints uses a process known as the five stages of development to identify and remove constraints ith bottlenecks.
The five stages of development are described in more detail in the following table.
The rate at which customer sales are revenues less variable costs really generally raw materials, sales commissions, and the work of goods are not regarded as a truly variable cost, unless the remuneration is 100 related parts produced.
The money that is related to the inventory of physical things, machinery and equipment, real estate, etc. Formerly known as OCD in the inventory.
The money spent to create a flow, other variable costs really e g payroll, utilities, taxes, etc. The cost of maintaining a given level of capacity.
In addition, Throughput Accounting has four key measures derived net profit, return on investment, productivity and Active investment.
In general, management decisions are guided by their effect on achieving the following improvements to priority.
The focus is the strongest by far the increase Throughput Essentially OCD said to focus less on reducing capital and operating costs and focus more on building Throughput sale.
Drum-Buffer-Rope DBR is a synchronization method of production of the stress while minimizing inventories and work in process.
The drum ” “ is the constraint the speed at which the stress works defines “beat” for the process and determines the total flow.
The buffer “ ” is the inventory level necessary to maintain a constant production It ensures that short interruptions and non-stress fluctuations do not affect the time constraint buffers represent; the amount of time usually measured in hours that the ongoing work is expected to arrive in advance to be used to ensure smooth operation of the protected resource Changes the more the process more buffers must be an alternative to large buffer stocks is overcapacity sprint ability intentional non-constraints in general, there are two buffers.
Buffer constraint immediately before the stress; protects duress.
customer buffer at the end of the process; protects the delivery schedule.
The rope “ ” is a signal generated by the constraint indicating that a certain amount of inventory was consumed This in turn triggers a release of the same size of the inventory in the process, the role of the rope is to maintain the flow without creating an excess accumulation of inventory.
Constraints are all that prevents the organization to move towards its objective in the manufacturing process, the constraints are frequently referred interesting bottlenecks, constraints can take many forms other than the equipment there he dissents on how to best classify constraints; a common approach is presented in the following table.
required or recommended working through informal means can be described example new employees “how things are done here” Examples include company procedures, eg how lot sizes are calculated, premium plans, policy overtime, collective agreements EGA contract that prohibits cross-training, or government regulations, for example, loaded pauses.
beliefs or habits ingrained For example, the belief that “we must always keep our running equipment to lower the manufacturing cost per piece” A close relative of political coercion.
Occurs when the production capacity exceeds sales on the foreign market is the flow Constrain If effective continuous application of the theory of constraints, eventually the stress is likely to move the market.
There are also differing opinions as to whether a system can have more than one constraint Conventional wisdom is that most systems have a constraint, and occasionally a system can have two or three constraints.
In manufacturing plants where a product mixture is produced, it is possible for each product to make a unique manufacturing path and the stress can “move” according to the path This environment can be modeled as multiple systems †one for each channel fabrication unique.
Political constraints deserve special mention It may come as a surprise that the most common form of stress is by far the policy constraint.
These may be particularly difficult because the political constraints often stem from established policies long and widely accepted to identify and even more difficult to overcome is usually much easier for an external party to identify the political, because outside is less already likely to take policies for granted.
When a policy constraint is associated with a firmly rooted paradigm ge “we must always keep our running equipment to lower the manufacturing cost per piece”, a significant investment in the training and supervision is likely to be necessary to change the paradigm and eliminate stress.
Policy constraints are not addressed by the application of the five steps of development the contrary, the three issues discussed earlier in the thinking process section are applied.
The thought processes are designed to work effectively with these issues and resolve conflicts that may arise from modification of existing policies.
A great way to deepen your understanding of the theory of constraints is to walk through a simple example of implementation In this example, the five stages of development are used to identify and eliminate a capital constraint ie bottleneck throttle in the manufacturing process.
In this step, the manufacturing process is reviewed to identify the constraint A simple but often effective technique is to literally walk through the manufacturing process for indications of stress.
If the constraint has been broken the normal case, recognize that there is a new constraint Search and disposal of the new strain is the new restart priority to the first step.
If the constraint is not broken, recognize what is required more work, and a fresh look should be taken, especially to check that the stress has been correctly identified restart at the first stage.
This step also includes a caution†attention inertia must remain vigilant and ensure that improvement is ongoing and continues the five stages of development are like “Whac-A-Book Mole”†stress down, then go right to the next.
Contrasting Theory of Constraints and Lean Manufacturing.
Theory of Constraints and Lean Manufacturing are both systematic methods to improve manufacturing efficiency, however, they have very different approaches.
The theory of constraints focuses on identifying and removing constraints that limit the flow Therefore, the successful implementation tends to increase the manufacturing capacity.
Lean manufacturing focuses on eliminating waste in the manufacturing process Therefore, the successful implementation tends to reduce manufacturing costs.
Both methods have a strong customer focus and are able to transform businesses to be faster, stronger and more agile Nevertheless, there are important differences, as highlighted in the following table.
From the perspective of the theory of constraints, it is more practical and less expensive to maintain a degree of excess capacity for non-constraints is a deliberately unbalanced line than trying to eliminate all sources of variation that is necessary to to effectively operate a balanced line eliminating the variation is always desirable TOC; it is simply given less attention than improve throughput.
Combining Theory of Constraints and Lean Manufacturing.
One of the most powerful aspects of the theory of constraints is the development of a laser on improving stress While Lean Manufacturing can focus more generally, it is implemented as a broad tool spectrum.
In the real world, there is always a need to compromise, since all companies have limited resources not all aspects of each process is really worth to optimize, not all waste worth the trouble of removing this background, the theory of constraints can be used very effective mechanism to prioritize improvement projects, while Lean manufacturing can provide a rich toolbox of techniques to improve the result †manufacturing efficiency is significantly increased by eliminating the waste parts of the system are the biggest constraints on the prospects and profitability.
While Lean manufacturing tools and techniques are mainly applied to the stress, they can also be applied to equipment that is subject to the constraint g e to equipment which starves or blocks compulsion; the post-tensioning equipment resulting in quality losses.
The rest of this section describes how to apply a range of Lean Manufacturing tools and techniques to the five stages of development.
The five stages of development of the theory of constraints can use the tools implemented lean manufacturing as shown in the diagram above.
Application of Lean tools to “Identify Constraint”.
Lean Manufacturing provides an excellent tool to visually map the workflow Value Stream Mapping and a philosophy that promotes spending time on the floor of the factory Gemba.
Value Stream Mapping VSM visually maps the flow of in-process states and come with a defined set of symbols and techniques.
Provides a base from which to work upon identification of the constraint, for example, the cycle time of each step may be marked on the map.
Teams and meshes useful for problem-solving exercises.
Gemba encouraged to leave the office to spend time on the floor of the factory This promotes a deep and thorough understanding of the manufacturing problems in the real world †by first-hand observation and talking with employees on the ground of 'factory.
Walking the floor of the plant, under production, and interact with employees can be a very effective way to gather information to identify the constraint.
Application of Lean tools to “Exploit Constraint”.
Lean Manufacturing strongly supports the idea of making the most of what you have, which is also the underlying theme for the operation of duress, for example, teaches Lean 5S to organize the work area, to motivate and Visual Factory Andon empower employees to seize the best standardized work practices and to exchange further ideas for improvement Kaizen.
5S is a program for the disposal of waste resulting from a poorly organized work space, it consists of five elements Sort eliminate what is not needed, will settle organize the remaining elements, Shine clean and inspect the area, create Normalize 5s standards, and sustain consistently apply the standards.
Creates a basis for better performance to the stress.
Enables faster identification of new challenges to the stress.
The results of motivation and greater pride in the improved working environment.
Visual Factory is a strategy to convey information through easily seen topsoil visuals are Andons visual displays that indicate the status of production and allow operators to draw immediate attention to problems so they †can be instantly addressed.
Displays the parameters by production constraints in real time †a powerful motivator.
Reduced the reaction time to stop by instantly alerting operators to intervene.
Allows operators to draw immediate attention to problems with stress.
Increasing development using visual to reinforce the importance of the stress.
Standardized work captures the best practices in the documents of the work area that are applied consistently by all operators and which are kept with the current best practice updates.
improves efficiency by consistently applying best practices to stress.
Reduces variation by applying standard procedures to stress.
Ensure that all settings and perform stress reproducibly operators.
Kaizen provides a framework for employees to work in small groups to suggest and implement further improvements to the manufacturing process It combines the collective talents of a company to create an engine of continuous improvement.
Provides a proven mechanism to generate ideas on how to exploit the constraint.
Identifies “quick win” opportunities to improve the flow of the stress.
Urges operators to work in a team and to critically reflect on their work.
Application of Lean tools to “Subordinate Constraint”.
Lean manufacturing techniques to regulate the flow and synchronization Kanban automated command line lines can be applied to subordinated and synchronization to the stress.
Kanban is a method for regulating the flow of materials, that provides for automatic replenishment by means of signals that indicate when to cards more materials.
Offers simple visual techniques to control the flow of materials.
Synchronizes the use of materials to stress the use of materials in the upstream process by controlling when new materials are released in the process.
Line of Control is an advanced technique used with automated synchronous lines, such as consumer products fast moving consumer goods lines, unconstrained equipment slave to the constraint so as to increase overall system throughput.
Provides an effective alternative to traditional drum-buffer-rope for lines of consumer products.
Optimizes stress and non-stress operating speeds to optimize throughput and reduce the frequency of minor stops.
Reduces startup delays constrained by equipment start synchronization.
Application of Lean tools to “Elevate Constraint”.
Lean manufacturing techniques to maintain proactively TPM equipment, which significantly reduces changeover times SMED, the fault detection and prevention of construction in the production process keyed, and partial automation equipment all Jidoka have direct application when the elevation of the TPM and SMED constraint can also be seen as operating techniques maximize throughput using the resources currently available; however, they are quite complex and are likely to benefit from working with outside experts.
TPM Total Productive Maintenance offers a holistic approach to care that focuses on proactive and preventive maintenance to maximize uptime of the increasing time pressure, reducing cycle times and eliminating defects .
Reduces the frequency of forced outages and minor stops.
Provides operators with a greater sense of “ownership” for their equipment.
Allows more maintenance is needed and provided for the non-production time.
Targets quality problems in finding and removing the root causes of defects.
SMED Single Minute Exchange of Dies is a method to significantly reduce the time of passage stress as many steps as possible are translated externally performed while the process is running and the remaining steps are eg bolts and streamlined manual adjustments are eliminated.
Increases production time used to stress.
Allows smaller lot sizes, which improves responsiveness to customer demand.
Enables smooth start, since a process of simplified and standardized change improves quality and consistency.
Poka-Yoke also called “mistake proofing” designs fault detection and prevention in the equipment with the aim of achieving zero defects.
Reduces the number of defects that is also very important post-tensioning.
Allows the operator to spend more time on autonomous maintenance.
Jidoka means “intelligent automation” or “automation with human touch” He acknowledges that partial automation is much cheaper than full automation Jidoka also highlights the automatic shutdown of the equipment for defects detection.
In some cases, the constraint can not be broken without significant capital investment Jidoka can provide valuable insights into the design and upgrades of equipment.
Improved focus on Constraint Manufacturing, development, improvement, manufacturing, constraint.