The Toolbox, Volume 4: Everybody Do the Poka-yoke

by Doug Paulin
Senior Manager, Logile, Inc.

Many individuals that find themselves managing labor programs do not have formal training in engineering concepts that are incredibly helpful to ensuring their success and the success of their company. The Toolbox looks to cover one of these concepts each month, providing useful instruction, templates, and tools that you can put into practice.

This month’s tool download: Poka-yoke Decision Support Tool

In this month’s installment of The Toolbox, we will look at a tool that process improvement experts use during the Improve phase for an existing process – where the DMAIC approach (Define, Measure, Analyze, Improve, Control) is used – or the Design phase of a new process that is to be developed – where the DMADV (Define, Measure, Analyze, Design, Verify Design) approach is used.

Have you ever observed a process in your business produce a product that you didn’t believe was up to your company standards? Have you ever witnessed a customer not receive the service that your company wants to provide to every customer? Of course you have – humans and machines alike are not perfect, and mistakes occur for many reasons. But how do we reduce defects, errors and mistakes without adding additional, non-value-added inspection and quality control labor into our operations? This is where poka-yoke can assist.

So what is poka-yoke?

Poka-yoke is the Japanese term for ‘mistake proofing,’ and the idea is that quality control is built into the process, rather than added as an additional inspection step. Would you rather add labor to your operation to identify mistakes and assign rework, or would you rather improve the process and minimize the mistakes in the first place? These solutions are often the simplest and provide benefits beyond just eliminating mistakes including decreasing fixed activity time like setup, increasing safety, reducing the learning curve for new employees and improving employee attitudes, among other benefits.

Examples of poka-yoke

So how do we deploy poka-yoke methodology into our operations? First, let’s make sure we understand a couple of simple examples of what poka-yoke is:

  • Manufacturing
    • Jigs and stops on machines that ensure when an operator inserts raw materials, the positioning dictates the measurements of the cut
    • Interlocking switches that prevent the machine from operating until a mechanical aspect is in a particular position. For example, a saw that will not operate until a bar is fully depressed, and the only way to fully depress the bar is to close it in such a way that ensures the operators’ hands are not in the cutting area
  • Retail
    • Automatic change-dispensing mechanisms that calculate and dispense the coinage due to the customer based on the transaction cost and the tender presented to the cashier
    • Point of Sale systems that prevent restricted items, like alcohol or medication, from being purchased until a form of identification is scanned and a confirmation is entered that the customer matches the photo on the identification
  • Healthcare
    • Sponge-counter bags utilized during surgery that have single-sponge compartments for sponges that have been used and removed from the patient. These provide a quick visual count of the sponges removed from the patient to ensure none are left in the patient
    • Automatic wheelchair brakes that engage when the chair is unoccupied. These chairs will only move when a patient is seated or a hand lever is pulled, preventing the chair from moving when vulnerable patients attempt to enter the chair

In the examples above, the operator or employee cannot proceed with the process until those steps are completed, ensuring items like measurements, safety, customer service and regulatory compliance are built right into the system. Poka-yoke can apply to your personal life as well. My favorite personal example is a tactic I employed when I began driving. In my excitement to take the car out I would often forget to grab my wallet (I had always been used to just storing my money in my pocket and the wallet was new to me). To avoid this, I started storing my car keys in the open bill-folds of the wallet – it was impossible for me to leave in my car without touching my wallet.

Activity and Service driven poka-yoke

So can poka-yoke be applied across industries and individual processes? Of course it can, but different industries and processes will apply different types of poka-yoke. The creator of the term and methodology, Shigeo Shingo, identified three types of poka-yoke when he developed the tool for activity-driven processes and they are as follows:

  1. Contact Method: Identifies product defects related to physical attributes (e.g., color, size, shape, etc.) through sensing devices (the first manufacturing example above is a contact method poka-yoke)
  1. Fixed-Value: Alerts the employee if a certain number of items, movements or processes are not made, usually in a process where the same activity is performed repeatedly (the first healthcare examples above is a fixed-value poka-yoke
  1. Motion-Step: Determines whether the prescribed steps of a process have been completed in sequence, usually in a process with several, distinct activities (the second retail example above is a motion-step poka-yoke – the employee must scan the item, then scan the ID, then press a button to confirming they believe the ID matches the individual)

So we have three types of poka-yoke that apply to activity-driven processes, but what about service applications? The customer engagement aspect of any process is also prone to mistakes, and there are poka-yokes that we can apply here as well. A misconception here though is that only the employee (often referred to as ‘Server’ in this situation) can make the mistake. That is incorrect, as the customer can (and often will, given they enter this process fewer times than the Server) make mistakes as well. Within the two classifications (Server and Customer), we also have three types of poka-yoke.

The Server poka-yokes are as follows:

  1. Task: Determines if a service task has been completed correctly (the first retail example above is a task poka-yoke)
  1. Tangible: Ensures the impression made on the customer (e.g., environment cleanliness, appearance, etc.) is in alignment with company standards (an example may be a full-length mirror placed by the timeclock in a retail environment with a poster displaying what the employee appearance should look like)
  1. Treatment: Encourages that the optimal social interaction between the Server and Customer (e.g., greeting, smile, questions, etc.) is achieved (an example may be a message on the point of sale screen that displays after the first item is scanned, notifying the employee to ask the customer if they found everything they were looking for)

The Customer poka-yokes are as follows:

  1. Resolution: Endeavors to remind customers their input is valuable to continually improving the business (an example may be providing ‘loved it’ and ‘didn’t love it’ waste baskets at a sampling station)
  1. Preparation: Attempts to fully prepare the Customer before they ever enter the service encounter (an example may be a sign communicating the wait time from that particular point in line for a single-queue style line)
  1. Encounter: Ensures that the Customer understands, remembers and/or pays attention to their roles in the service encounter or the nature of it (an example may be requiring the customer to insert a coin to utilize a shopping cart, which reminds them it is their role to return the cart to a proper location to get their coin back)

Build mistake-proofing into your processes

So now that we have identified the different poka-yokes available for activity and service based processes, how do we identify opportunities to build mistake-proofing into the process? The tool provided in this installment (download link provided at the top of this post) is a process flowchart, which is a type of Decision Support System that will help you identify the steps to follow based on a series of questions.

The first question to ask is rather obvious but often overlooked – are there recurring mistakes in this process that we must address? Remember, the entire point of poka-yoke is to simplify the process by building mistake proofing into the process. Are your customer-engagement scores consistently low? Is your shrink in a particular department higher relative to other departments? Do you routinely have noncompliant temperature readings on production food items? These are critical business processes where mistakes are occurring somewhere. Once you have identified the activity producing the undesirable mistake (perhaps through the use of a Fishbone Diagram?), you can deploy this installment’s tool to identify what type of poka-yoke is applicable.

Work through the flowchart, answering each question (i.e., Is the process activity or service based?) until it recommends a type of poka-yoke to deploy (e.g., contact method, fixed-value, treatment, etc.). Once you have determined the source of the mistake and the poka-yoke that may address it, go observe the process in question, ensuring that you understand your company’s Standard Operating Procedure (SOP) so you know exactly what you should be seeing. Watch it once. Watch it twice. Watch it until the mistake is so apparent that you can’t stand not addressing it. Put yourself in the shoes of the employee and ask yourself ‘what would I wish I had to make this easier?’ The issue may be that the employee is not following SOP. The issue may be that the cause of the mistake is the SOP itself. Regardless, poka-yoke can be applied.

Return to the tool from this installment, where numerous types of poka-yoke ideas are listed by type on the second page. If nothing else, the reference poka-yokes should serve as a source of inspiration for a poka-yoke that will address your mistake. Remember, the point of the poka-yoke is to build mistake proofing into the process. The idea should be rather simple, make the job easier, and, if not make it impossible, make it very difficult to complete the process if that mistake is still being made.