The story exemplified in Ely Goldratt in his famous book “The Goal” about a team of “Scouts” on a camping trip was an excellent example exhibiting the role of a bottleneck and its impact on the overall progress of the team. The slowest member in the chain controls the pace of the progress and the key focus of TOC (Theory of Constraint) is to manage and improve the slowest member or the bottleneck. TOC helps manufacturing companies to identify the bottleneck and focus resources to elevate the constraint. Lean experts look at the same example a different way. Lean fundamentals explore and understand the supply chain. Lean would have taken the same team of “Scouts” and determined the rate of each member – analyzed the “takt” time and balanced the carrying load for each member of the team so that the entire team moves at a uniform pace. Lean approach to manufacturing is ensuring that the processes are balanced and run per the “takt” time as determined for the customer demand.
Lean principles will enable the team to move at a uniform pace with minimum amount of inventory (distance) between the members. Lean takes a holistic approach to design the effective supply chain (line balance) and recognizes the nuances in the supply chain constraints to create a uniform flow across every unit in the chain. TOC on the other hand is a more focused approach to address the bottleneck. TOC is a good solution for factories which have less control or foresight into the demand product mix and are continually re-planning to determine the optimal way to schedule the demand to meet delivery performance. Usually this model, the variability in production causes reliability issues for the people, process, machine and materials in order to satisfy the four requirements of an efficient and effective supply chain is cost, quality, safety and delivery performance.
A good analogy of a Lean and TOC practice is the human body. Every person has a different metabolism of absorbing the calorie intake. In a Lean model, the person has knowledge of its metabolism and creates a corresponding diet plan. The diet plan, if maintained, will ensure that the body remains lean. The diet becomes a habit and all corresponding activities of ensuring the right diet is available and regular health checkup are planned easily. A regular exercise schedule is laid out which ensures that the body stays in shape. The exercise schedule is based on the variability in the calories intake. If the variability is high then a regular strenuous exercise is laid out – which buffers that body against the variability. Variability in the diet is taken into account while planning the exercise routine. TOC model is useful when there is a lack of regimental schedule and the body has to react to the changes in the diet. The emphasis is not on the calorie intake but on the process of burning the calories. If on a certain day the calorie intake is high, the body meter indicates that the exercise schedule has to be strenuous. If TOC determines that exercise is the bottleneck, it will plan for extra time on the stair-master, to burn the extra calories. Lean and TOC both address the metabolism and try to keep the body lean. Lean dictates that the body metabolism has to be understood and set up all the activities, including diet and exercise plan, to meet the body’s metabolism requirement, while TOC will quickly address the variability by addressing the bottleneck and focus on making it more efficient. Both the processes require continual evaluations to reset the regiment. Although it may look better on paper that one could only focus on the bottleneck rather than take a holistic approach, it causes uncertainty and irregularity in the schedule which can become cost prohibitive in the long run.
The human body is an embodiment of perfect manufacturing environment. It is a learning system which processes massive amounts of data, provides visibility, makes decisions and reacts to variability.
Love to hear if you agree or disagree.
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