Lean Management Tools

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Poka Yoke (Mistake Proofing) 

The Poka-Yoke lean management tool is all about mistake proofing, or avoiding errors within your organisation. This ensures that the appropriate conditions are in place prior to a process or new step being executed, which will stop defects in the first place.

Sometimes it is not possible to detect where a defect may come about before it has occurred. In this instance, poka-yoke will act as a defence function.

It stops errors as soon as possible by bringing attention to the error that cause it (whether this be human, mechanic or process based).

This may involve adding design features that will make it impossible for errors to occur, or reevaluating the whole process therefore ensuring quality products and services.

Most organisations will have processes that can allow for mistakes to be made along the way.  If your organisation adopts the poka-yoke tool, this will help in decreasing the errors made.

Mistake proofing techniques (poka-toke) will support your organisation and its customers in many ways, such as:

  • The reduction of work place errors means there is a reduction in waste, cost and the time it takes to get the final product to customers.
  • The organisation will have strong processes that work reliably, are predictable and work better with other organisational processes.
  • There will be less time spent on training workers in areas that aren’t needed
  • Your organisation will have a built-in quality control system, making auditing easier


When to use Poka-Yoke and how?

As mistakes can be made anywhere in the business, this means that Poka-Yoke can be implemented anywhere across the business. An organisation can apply Poka-Yoke to any type of process, helping it prevent errors.


Poka-Yoke Steps

The steps in implementing Poka-Yoke are as follows:

  1. Identify the Process or operation that it needs to be applied to.

  2. Analyse the 5-Why’s & the possible ways this process may fail. 


    This rule is as simple as the name suggests, and is where you must ask yourself ‘Why’ 5 times consecutively in order to find out why something is occurring or behaving that way. By doing this, you will slowly but surely be able to peel away the layers to a problem, eventually finding the root-cause of it. More often than not, the supposed answer to your question will actually lead to asking another question rather than the final solution.

    In regards to the Poka-Yoke technique, let’s use the example of customer satisfaction being low around the products they are getting delivered. The 5-why analysis may look a little something like:

    “Why are the products shipped not meeting satisfactions?” Because they are taking longer to get there than when initially said
    “Why are they taking longer to get there than initially said?” Because there is a new team of casuals in the dispatch department who haven’t had adequate training.
    “Why have they not had adequate training?” Because the head of this department is currently on annual leave, meaning they have been trained by a step-in employee

    As you can see, a root-cause has been found, which was down to a training issue. Now that the organisation is aware of this, they can allocate some extra time to this training and implement steps that will allow them to send products on time.

    Don’t get too caught up on the name - ‘why’ may only need to be asked 2 times in order to find out the root-cause of a problem, or conversely, it may need to be asked 15 times.  This will depend on the length and scope of the process you are investigating and how many people are involved with it.

    Select a Poka-yoke approach that is appropriate to the process

    For example, a shutout approach might be used when errors need to be prevented, while an attention type may be more appropriate to highlight the error has already been made.
Decide whether a contact, constant number or sequencing method is most relevant.

Depending on what has been chosen, an operator will either be alerted before a mistake is about to be made, not allowing the process to carry on any further, or they will be alerted right afterwards, allowing them to step in and intervene.

  • Contact: Detect the error of a product using a physical attribute such as the shape or size of something
  • Constant Number: An error will be triggered if a particular number of movements or steps are not made
  • Sequencing Method: Using a checklist to make sure all process steps are carried out


Test the Poka-Yoke method selected. 

This may take some time depending on the scope of where it is being implemented. It is important not to rush this step as is the method selected does not work during the test, it won’t in real life either.

Train the manager on the method, review and measure.


Other Lean Management tools: 

Click here to find out what lean management is (and the 8 wastes of lean)