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Glossary of Six Sigma Terms: Letters J – L


  • Jack in the (Six Sigma) Box.

    Jack in the Box is a type of variable in Lean Six Sigma. Represented by x, it appears at arbitrary intervals during a manufacturing process. This is because of various external factors without cause. While Jack in the Box is less useful when creating an FMEA, it is unique among Six Sigma tools. As such, the Jack in the Box was substantial enough to affect process capability as it appears. For example, if you were performing benchmarking of a credit cards process, your Jack in the Box would be that your employees decided randomly to apply for pre-approved cards for their family. You would not be able to track the cause as the applications were made randomly and for no discernible reason. Although this depends on whether the number of cards issued was significant enough to affect the baseline.


  • Jidoka. 

    One of the two pillars of the Toyota Production System, jidoka is a core principle that drives success. Like just-in-time, jidoka allows you to highlight problems easily as they appear. Jidoka is a Japanese word that translates as “automaton with a human touch.” Jidoka means that workers on the production line can stop the process when a problem occurs. Following jidoka, they can then prevent the manufacturing of defective products. Following jidoka allows you to devise methods to improve the quality of your processes. Jidoka also helps you to highlight and eliminate the root causes of problems like defect.


  • Just-in-Time.

    JIT, or just-in-time, is a type of planning strategy used in manufacturing processes to optimize availability of resources. Look at the material inventories for your manufacturing sites in terms of what, when and how much is required. JIT is also a type of pull system where you pull the product along until you have finished. As opposed to the traditional method of mass production, the push system. JIT uses tools such as Kanban, Andon, and cell layout in Six Sigma. Related tools included shojinka, smed, jidoka, poka-yoke, as well as kaizen.



  • Kaizen.

    Kaizen is another Japanese term, meaning “continuous improvement.” It is a method for generating a culture of continuous improvement in the workplace. Professionals often use Kaizen in Lean Production and Lean Six Sigma. A product of the 20th century, Kaizen started appearing as traditional thinking processes started to lose efficiency from aging tools, equipment, and machinery.

  • As efficiency decreases, so does productivity. Kaizen aims to counter this, focusing on maintaining equipment continuously, to prevent breakdowns and loss of efficiency and productivity. It also aims to create a work culture wherein employees actively work towards maintaining a standardized level of quality as time passes. This may involve making minor modifications to better tailor machinery to the processes they serve or improving the staff capability through training and regular coaching. Kaizen isn’t just for Black Belts and management types. Kaizen is for everyone to practice. In fact, it relies on a completely comprehensive team effort if you’re going to drive continuous improvement.


  • Kanban. 

    Lean Production comprises many pull systems, but the most popular and well-known is Kanban. Kanban is a ‘single card system.’ Unlike traditional push systems, Kanban involves products being made in small batches to satisfy immediate and current demands. Each batch should only be adequate for several hours’ consumption before the system requires a new batch. As a pull system for production, one of Kanban’s primary tools is the Kanban card, which authorizes production, representing all of Kanban’s principles.

  • When you make a batch of products, a Kanban card will travel to the next stage of production, and from there is returned to the original production station. As each Kanban card returns, they authorize the next batch to be made and sent out. Kanban works in a cyclical trajectory to ensure production keeps moving at a constant rate. However, if your production station does not possess any Kanbans, it cannot produce anything. As such, when demand starts to slow down, or even stops altogether, the rate of production slows down, or stops, as well.
  • While the production station will discontinue production (producing to ‘get ahead’), Kanban forces efficiency by reducing unnecessary inventory. This will prepare the station for faster changeovers, making them more responsive and productive. Similarly, creating small batches helps prevent irregular workflow, minimizing the number of stockouts.



  • Latin Square Design.

    You use a Latin Square design in experimental design (design of experiments) as a method of blocking for two variables. Your treatments are represented by Latin letters A to E, in varying sequences. This design may be restrictive, due to the number of variations of each blocking variable. All of the variables must be equal to the number of treatments.

  • To draw a Latin Square design, you should create a table with seven rows, split down the middle. On the left side of the design, you will have seven boxes running across to the center line. The second box down should be labeled Material Batch (first blocking variable), and the boxes below labeled 1 to 5. On the right, you should label the top box as ‘Operators.’ Below this, you need five columns, which will create six small boxes for each column. Label the top boxes 1 to 5, and fill each box with the appropriate letter. For example, the first column may list the letters in sequence, A-B-C-D-E, while the next may be out of order. Black Belts and Green Belts are mostly likely to use Latin Square designs.


  • Lattice Design.

    There are many tools you will have to learn in Six Sigma work, such as the lattice design, a type of Mixture Design. Lattice designs appear as a triangle, with each corner marked, representing a single ingredient in your process. Similarly, additional marks (usually circles or dots) appear at the midpoint of each side. This creates a 50:50 mix of two ingredients in your process. While the lattice design may appear to be very limited, there are augmented and extreme vertex varieties for more complex circumstances. Practitioners often prefer these alternatives for their Six Sigma and Lean work, given the density of the data involved. You should also take note that a typical mixture design may have numerous ingredients, though it is often more convenient to illustrate it with only three. Black Belts and Green Belts, those involved in data-oriented work will usually be required to create lattice designs.



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