Optimizing individual processes does not help throughput as much as optimizing for the entire process throughput. Rather than sub-optimizing at too low a level, focus on the bigger picture.

The biggest difference between the Theory of Constraints and Lean is the idea of subordinating local optimization to global optimization for the entire system’s throughput. Goldratt himself stated that the Theory of Constraints tells you where to look and what to change, while Lean tells you how to change.

  • Global optimization with local action (like Pull in Lean).

  • Find the constraint or bottleneck.

  • Decide how to handle the constraint using Lean.

  • Subordinate everything else.

The Theory of Constraints includes an idea it calls drum-buffer-rope. Briefly, this concept means the drum sets the pace or ‘beat’ of the entire work flow system. To meet the drum pace, we need to protect the constraint from lost capacity due to unexpected problems. We protect it using a buffer. However, buffers or queues can increase inventory. So to help protect against too much WIP inventory, we only want to start another work item after the main constrain finishes one. So a rope is figuratively tied between the constraint process step and the upstream starting process step to gate or choke the workflow system. This is similar to the Los Angeles freeway on-ramp example that stops cars from entering until the preceding cars have entered the traffic flow. The TOC drum-buffer-rope idea originated from manufacturing. We see the TOC drum-buffer-rope idea as the nearly the same as pull in Lean. We also find it tends to be easier to explain to knowledge worker staff involved in training, "Don’t pull another work item card until you complete one." So going forward, we won’t mention drum-buffer-rope again. We’ll only talk about Lean pull instead.

We look for bottlenecks on our Kanban board as part of the daily scrum/standup meeting.

We recommend the book, Velocity: Combining Lean, Six Sigma and the Theory of Constraints to Achieve Breakthrough Performance - A Business Novel. It is written as a story to more effectively show the principles of the Theory of Constraints in action. It is aimed at manufacturing, so the reader will need to interpret from that domain to the training domain.

Applying the Theory of Constraints to avoid sub-optimizing helps an individual instructional/LX designer realize that simply improving their own personal workflow does not necessarily improve the overall throughput of the entire development team. Even when the instructional/LX designer is the primary constraint, there are still practices in Agile that can improve the overall team’s performance.

People are often not used to global optimizing when traditional metrics have looked at utilization of machines and people (sub-optimizing) rather than measuring improvement in the entire process throughput. We use TOC to set WIP limits.

Another challenge for training professionals is seeing all of our unfinished work products as "inventory." Just like in manufacturing, increased inventory is waste.


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