Understanding Constraint

Understanding the concept of a ‘constraint’ is the first step towards understanding the Theory of Constraint (TOC). An example of a chain is taken in this section to explain the definition of constraint as per TOC and to highlight the importance of identifying the right constraint.

The chain, taken as an example here, has various links and can hold up to 30 kilograms of weight. However, there is one single weak link that can hold only 20 kilograms of weight. Due to this weak link, the total weight that the chain can hold will be reduced to 20 kilograms only, or else the chain will snap at the weakest link with any amount of weight above 20 kilograms. Hence, the entire capacity of the chain is limited to the capacity of its weakest link.

In the example above, the weakest link in the chain is the constraint. A constraint is defined as a limitation of a system which restrains it from achieving the desired level of performance. A constraint thus determines the maximum capacity of a system. There are many ways that constraints can show up, but a core principle within TOC is that there are not tens or hundreds of constraints – it is just one or at most a few in any given system.

Constraints can be internal or external to the system.

An internal constraint is in evidence when the market demands more from the system than it can deliver. If this is the case, then the focus of the organization should be on discovering that constraint and following the five focusing steps to open it up (and potentially remove it).

An external constraint exists when the system can produce more than the market will bear. If this is the case, then the organization should focus on mechanisms to create more demand for its products or services.

Referring to the example of the chain again – What is the main objective or goal of the chain? For this example, the chain’s objective is to lift a load. Any owner of this chain will be concerned with either of these: How much load the chain can hold? Or how much load individual links of chain can hold? However, what is important, considering the objective of bearing a certain load, is the overall capacity of the chain as against the capacity of individual links.

The same reasoning can be applied to a system as well. The goal of a system as a whole is far more important than the goals of its individual elements. This holds true because: When it comes to delivering a product, the customer is more concerned about say, the final delivery date as against the time taken by individual tasks. The only thing that can hamper the final delivery date or the true goal of the system – is nothing but one of its elements, one of its tasks, one of its weak links.

The next section will explain the Five Focusing Steps that help in identifying, exploiting and removing constraints.