Identifying the Critical Muda Variables


The first step in developing change capability is to involve cross-functional focus groups in muda awareness exercises to help them understand that they have improvement opportunities. The second step is to give these focus groups muda elimination challenges on which to work.

Let’s consider, for example, the classic lean improvement variable of reducing machine changeover time. Here the critical muda variable is the time taken between the last good-quality workpiece from the previous batch to the first good-quality workpiece of the next batch. Traditionally, the total CO time in a given period is reduced by increasing the batch size. The actual CO time was considered to be a fixed parameter for operations management.

Now let’s focus on CO time in more detail. You go to the machine, make a video of the changeover, and measure 60 minutes. When you look at the video, you see many inefficiencies and opportunities for improvement, which show that CO time is not a fixed parameter but something that can be minimized and improved. Who should be looking at the operation and the video with you? who should be aware of the CO time and the sequence of tasks? First are the CO operators, the people who actually execute the task; second are the supervisory of these workers; and third are the suppliers of these workers. This is effectively the focus group.

In this way we can define many specific critical muda variables that can contribute to improving operations and achieving basic reliability. At the same time, we are starting a change-capability improvement process.

Critical muda variables can be the time an operator takes to perform a task, the number of defective parts, or the amount of inventory.

What are the critical muda variables that are important to creating awareness in terms of pull flow? In production flow, the most important variables to be aware of are those that affect the work in process between operations and the machine CO time. The main flow variable is lead time, which can be estimated as the quantity of inventory transformed in a certain number of sales or production days. One of the causes of muda is the accumulation of WIP as a result of the absence of one-piece.

In terms of logistics flow, the most important variables are the components of the total lead time within the pull logistics loops. The key drivers here are the lead time for information flow and the lead time for materials flow. In terms of basic reliability, the critical muda variables affecting these are operator absenteeism, machine availability ratios, stock-out ratios, and defect ratios.

Acknowledgement: KAIZEN in logistics and supply chain book by Euclides coimbara

In case you missed it, my last post was creating change Capability and Basic Reliability

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