Are you familiar with the “five focusing steps”? This approach is at the heart of the Theory of Constraints (TOC), the school of thought initiated by Dr. Eli Goldratt, author of the bestseller “The Goal.”
Having identified our major constraint and optimized its exploitation, we are now going to subordinate the company’s other resources to this constraint.
Subordinate Resources
In our participative companies with flattened hierarchies, the term subordinate resources can be misunderstood. In fact, a hierarchy of resources has been established. If we have identified critical resources, our constraints, it’s because we recognize that they are our most precious resources and need to be protected. Other company resources—for example, workstations before and after this constraint—must be subordinated to it.
Capacity Buffers
A few years ago, we carried out a project at a metallurgy plant. There was no ambiguity about the site’s major constraint: a monumental annealing furnace, through which all the site’s major flows passed, was fully loaded 24/7. Securing this throughput was essential to maintain flow.
Upstream, there were several process stages that were not fully loaded. These stages had what we call capacity buffers: equipment with a margin of spare capacity. These resources may encounter problems—such as breakdowns—but thanks to their available capacity, they are likely to catch up. Production supervisors ensure that these capacity buffers are managed without disruption.
As we’ve seen in previous articles, a time buffer—or queue—was established at the entrance to this furnace. As long as contingencies do not exceed the duration of this time buffer, all is well. The upstream stages are subordinate to the constraint, and it’s up to production supervisors to ensure that the major constraint is always protected.
One upstream piece of equipment averaged around 2.2 shifts, operating in 3×8 shifts, maintaining a margin of capacity. However, productivity was low. The production manager decided to reduce shifts, thus saving on labor, but this decision backfired. The site’s major constraint suffered as it was no longer sufficiently fed, resulting in a loss of sales. This incident illustrates the “crime of insubordination”: everything must be subordinated to constraints.
Active Monitoring of Capacity Buffers
In Intuiflow, we monitor the load on non-constraints, both upstream and downstream of the major constraint. Upstream, it is essential to keep the major constraint active; downstream, it’s important to absorb its output, to avoid blocking production due to limited space or other issues. The resource load graph below illustrates an example of a capacity buffer.
A capacity buffer is not scheduled at finite capacity—only constraints are. We avoid extending lead times due to an overloaded capacity buffer. In case of a 50% overload, production supervisors can take action, such as bringing in extra labor or adjusting schedules.
Active Monitoring of Time Buffers
To ensure each capacity buffer effectively protects downstream constraints, each resource’s program displays the status of production orders within the time buffer. For instance, red-highlighted production orders require immediate processing.
For example below – orders in red must be processed first, followed by green orders. This status evolves in real time and gives unambiguous priorities.
Notably, the upstream station should avoid grouping production orders in a way that jeopardizes the schedule of the major constraint. We subordinate resources at every step.
Standing Meetings
Production meetings focus on protecting time buffers and ensuring resources are subordinated. In modern factories, SQCDP communication points are common. However, during site visits, we often find that lead time or service isn’t consistently measured. With the DBR logic, our mission is clear: protect the downstream control points.
Support Teams and Gemba
Support teams, such as maintenance, procurement, and HR, must also be subordinated to the major constraint, ensuring they are aligned in delivering timely support. Ultimately, we are all subordinates of the Gemba—the workshop where value is created.
Stay tuned for the next blog in this series, as we explore the “4-Elevate” stage.
Missed the first two steps? Head to our blog page to get caught up!
