Tempered Lean & Theory of Constraints (ToC)
Will Brennan
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Theory of Constraints (ToC) is a concept that is used in project management, as well as manufacturing, and other interdependent processes - and it works well with Lean (mostly). It refers to a set of constraints which must be met in order to achieve a specific goal.
The basic premise of the theory of constraints (ToC) is that there is a minimum amount of resources available to achieve a specific outcome, and many systems do not use them efficiently, or take into account statistical fluctuations, or add exceptions for when Murphy throws a wrench into your process.
If those resources are used up before they can be converted back into desired outcomes, then the result will be negative. This is only one of many possible negative undesirable effects "UDE's".
The key to ToC is to find a system within a project that limits the available resources. These constraints must be a key part of the process, otherwise, you would remove them, right?
For example, in a project which aims to produce a series of widgets, the resource limit may be set by the amount that the machine capable of making the widgets has. If the project is successful, the machine is able to manufacture the widgets at the required rate. If the machine is unable to manufacture the widgets, then the project will be a failure.
By working with the constraint, which dictates the overall flow within the system, you can actually achieve greater throughput. An example would be making sure not to pass a defect through a constraint, which aligns with Lean. Another option may be to reduce any downtime at the constraint, or eliminating scheduled downtime during the working hours for that machine (assuming it doesn't run 24x7). Or maybe, some things don't actually need to pass through the constraint at all to get the desired final product.
ToC does not only apply to physical resources. It can also apply to people. A manager has a goal to improve the quality of the team. To do this, they may conduct a testing exercise. The manager wants to find the best candidates for a new job. The test is usually set to a certain threshold. If the candidate passes the test then they are deemed suitable.
Another use of the theory of constraints is to identify potential threats to a project or process. A manager may want to identify areas where there may not be enough resources to complete the project. In this case, advanced knowledge of ToC can often allow for restructuring the project, the process, or the people in order to satisfy the new requirements and account for the threat or UDE's.
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The theory is based on multiple variables. The next important variable is optimum. An optimum is the end result which is achieved by using the resources. Often what you think a process can do and what it is actually capable of achieving is 1.5-2X or greater once examined closely. Looking at the data in-depth and re-thinking how the process is done is the key to finding the optimum throughput with the tools available.
The final variables are constraint drivers and "old" constraints. A constraint driver is an element which could change the optimum. The constraint drivers are usually related to external factors. A good example would be the weather in an outdoor process. If the weather is bad, then the production rate may be reduced. You can't control the weather; or maybe you can by covering the work area in some fashion.
What is an "old" constraint? It's the notion that in a certain process the maximum achievable is X units or a speed of X, however, this may have been true with "older" equipment, a prior process, or a previous group of people (IE, a company buy-out or a management or personnel transition). In this case, the constraint isn't real, it's mostly embedded in the current work process and in the minds of the personnel.
So, in a Lean process that wants more throughput on a consistent basis without necessarily having to add new people or equipment, how does a plant or project manager achieve this?
It comes down to knowing more about ToC and what to change, what to change to, and what to do to cause the change.
Note: Thanks for reading this; should you feel these are helpful, or can be made simpler, please let me know. Also, if you do enjoy these or have other colleagues who may benefit, please do share. I'll endeavour to try to keep these simple but not simpler (or around a maximum of 800 words).