How does the Theory of Constraints compare to Lean?

The Theory of Constraints and Lean are two of the main approaches to improve the performance of industrial organizations. How do they compare? Can they be combined? Our point of view regarding ToC and Lean.

What is the Theory of Constraints (TOC)?

Sometimes referred to as Constraints Management, the Theory of Constraints (ToC) is the least-known and least-used of the main approaches used to improve industrial performance. Developed by Eliyahu Goldratt in 1984 in his bestselling book “The Goal”, the Theory of Constraints hypothesizes that every organization has at least one constraint (or bottleneck) that limits its growth. Constraints Management therefore provides a set of tools (e.g. “The Five Focusing Steps”) to identify and manage those constraints, thereby increasing productivity and profits.

What is Lean manufacturing, or the Toyota way?

Lean manufacturing is an approach that grew out of the Toyota Production System in the middle of the 20th century. The Lean methodology focuses on minimizing waste within manufacturing processes, while simultaneously maximizing productivity. Waste is seen as anything that customers feel does not add value and are not willing to pay for. Lean manufacturing is therefore centered on preserving value with less work, with the ultimate goal of providing perfect value through a creation process that has zero waste. Some of the benefits of lean thus include reduced lead times and operating costs, as well as improved product quality.

How does the Theory of Constraints compare to Lean?

There are many similarities between the Theory of Constraints and Lean, which is not surprising given that Goldratt’s work originated from many of the same sources and previous work that Toyota used to develop the Lean manufacturing approach. Their main point of agreement is the need to focus on the throughput of the whole process, rather than on the performance of individual process steps. 

Both Lean and Theory of Constraints have a strong customer focus and can transform organizations to be faster and more profitable. However, they have different approaches to do so. Constraints Management indeed focuses on identifying the bottleneck and increasing the throughput of that bottleneck, leading to increased manufacturing capacity, while Lean Manufacturing focuses on eliminating waste from the manufacturing process, thereby reducing manufacturing costs. With the Theory of Constraints (ToC), the pace is set by the constraint, whereas with Lean, it is set by the customer (“takt time”).

Combining Lean with TOC: a wining cocktail?

Combining Lean and ToC is possible, highly recommended and can lead to much faster improvements in manufacturing processes, as well as a significant increase in sales. While Lean manufacturing eliminates waste, the Theory of Constraints identifies bottlenecks on which to act to improve profitability. Combining ToC and Lean manufacturing thus creates a virtuous cycle, in which the organization becomes continuously more efficient by eliminating added expenses and simultaneously generating additional sales that can absorb the productivity improvements.

Theory of Constraints is often used to identify the bottleneck, then the Lean Manufacturing tools can be used to improve the performances of this constraint, and so improve the overall performances. If this constraint is eliminated, then the ToC advise to look for the next one, when identified, Lean tools can also be used to improve these new constraints. Combining the 5 Focusing steps of ToC and the Lean methodology is a powerful way of improving the performances.

Implementing the Theory of Constraints and Lean with Marris Consulting

Marris Consulting is an expert company in Theory of Constraints and Lean We offer both ToC and Lean training, consulting services and are able to help you combine these two approaches to drastically improve your organization's performance. For more information about our services, please do not hesitate to contact our team of operational excellence consultants.

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