6. What happened to the Theory of Constraints?

The Theory of Constraints (TOC) was popularized by a well written and entertaining book entitled “The Goal” that we all enjoyed reading (Who can forget Herbie?). The concept is still around today although you don’t hear as much about it two decades after the book came out. Unfortunately while the book was entertaining it took a single concept and tried to turn it into an entire business system. Managing your bottleneck is an important consideration in many businesses especially process intensive ones or industries that can sell everything they make (think oil wells or gold mines) but in other instances improving the bottleneck might only lead to over production and a whole assortment of other wastes. The main thrust of this system relies upon the notion of drum, buffer, and rope. The drum is the speed of the constrained process, the buffer is either time or inventory that ensures the constrained process is not disturbed, and the rope is the material tied to or released to the constrained process. If you can tie the rate of the constrained process to that of the customer then you can avoid the perils of over production and the assorted wastes that come along with it. But with many processes it starts to get complicated in practice. Other “work-arounds” have to be developed as well to apply the concept in most cases. Normal production scheduling methods in TPS have more shop floor proof of concept and application history.