Poka-yoke: Examples of Mistake-proofing in Different Areas

Poka-yoke: Examples of Mistake-proofing in Different Areas
Poka-yoke is a technique that helps to avoid mistakes in the manufacturing process. This Buzzle article enlists some examples of mistake-proofing in different fields, like technology, and daily life.
If you look at a surgical environment, a poka-yoke approach to packaging may prevent staff mishandling equipment whilst setting up, not only to avoid errors, but also to help maintain the sterility of devices used in surgery. With human error continuing to account for such a high level of patient harm, even when experienced professionals are involved, the impact this could have is huge.
Paul Greenhalgh, Director of Design, Team Consulting
Mistake-proofing comprises methods that help avoid mistakes. This is especially important in the manufacturing industry, where personnel involved in the manufacturing of any product or device, be it machines, compressors, computers, hardware tools, workshop devices, etc., should possess a knowledge of the production process and the use of the product so that the end user does not hurt himself.
This method of mistake-proofing has helped unearth many production glitches, and has considerably improved product quality in many industries. In the paragraphs below, you will find some examples from different fields that support this theory.
Background
  • The word 'poka-yoke' is of Japanese origin.
  • 'Poka' in Japanese means 'mistake' and 'yoke' means 'prevent'. This roughly translates to 'preventing inadvertent mistakes'.
  • The term was coined by Shigeo Shingo, in the 1960s.
  • Shigeo Shingo was in charge of the statistical process control of a leading Japanese manufacturing plant in the 1950s, but was always dissatisfied with the statistical approach regarding untested devices.
  • In the early 1960s, while visiting an electrical plant, Shigeo Shingo designed what is believed to be the first poka-yoke device, in order to manage the defects regarding the push buttons of a small switch.
  • He realized the importance of mistake-proofing, and consequently, developed and worked on this concept for the next few years.
  • As of today, the concept is not only popular in Japan, but all over the world.
Design and Application
  • The poka-yoke devices are designed to be very simple and cheap. This is to maintain the cost-effectiveness.
  • They are incorporated as a part of the production schedule itself. For example, a few years back, certain cars had a device that would not let the engine start until the driver was wearing his seat-belt.
  • They are mostly designed to be close to where mistakes tend to occur. This is done so that the user can immediately identify where the mistake is, and he will be given a warning anyway.
  • The application of this concept is manifold, it is used extensively in manufacturing, software, electronics, traveling, hospitality, and even in daily life.
Types of Detection and Prevention
In large productions, 3 types of methods are used for detecting and preventing errors. They are:

Contact
It recognizes defects by testing the physical attributes of devices. This includes the size, shape, color, etc.

Fixed-Value
It sends out warning signals if a particular movement is expected but is not made.

Motion Step
It tests if the procedure has been properly followed, step-by-step.
Simple Example
Charger and Connector
Charger and connector
The above figure shows a charger and connector. All the three pins need to fit perfectly within the three slots provided. This has to be monitored during production. And for that, the design phase of the product needs to be executed perfectly as well. A slight error in the calculation of the slot-size or the pin-size can make the device redundant or faulty.
Computer Monitor Cable
Monitor cable pin
You must have dismantled your CPU a number of times. Have you noticed how all the cables and connectors fit into their respective slots with the right precision and accuracy? This is because of mistake-proofing. While manufacturing these cables, the operator needs to take care the right pins are secured in the insulator, and the exact number of slots are drilled for perfect placement. If this is not done, the device will definitely not work.
Manufacturing
As mentioned previously, this concept has found an enormous use in the service, manufacturing, and production industries. Some of the devices that come under this category are:
Alarm Systems
Alarm Systems
They are activated with alarms for security purposes. If an unauthorized person enters the bank, or the electric circuit of the door bell catches fire, a warning alarm rings, which ensures that you can take care of the problem before it gets out of hand.
Fingerprint identification
Fingerprint identification
This is used extensively in biometrics, forensics, detective agencies, etc. Every fingerprint in the world is unique, no two are ever the same. The device is such that only the fingerprint of that particular person will be required as input. Trying to replicate or use some one's fingerprint forcibly will not work either.
Workshop Devices
Workshop Devices
They are embedded with a variety of protective devices, and these include the jobs relate to smithy, carpentry, lathe machines, etc. The protective poka-yoke ensures that:
  • There is enough space between the operator and machine.
  • It is shock-proof.
  • Gives out warning signals in case of incorrect procedure.
Car Keys
Car Keys
Cars are protected in the sense that the car keys cannot be removed if the auto transmission is in an unsafe mode. Also, there is safety device to make sure that the key is in an 'on' position when the car needs to get out of the parking zone.

Some other devices in this category that use safety mechanisms are radar systems, auto breaking, electronic doors, traffic alerts, digital security systems, light curtains, electronic baggage tags, electronic waiter pads, validation testing tools, auto pilots, queue management systems, color-coded systems, etc.
Hospitals
Health-care systems need to have extremely able and appropriately-designed safety systems, because the equipment is being used for patients. A small error can put a patient's life at stake, and hence, the devices used need to completely protected.
Dialysis Machine
Dialysis Machine
These machines perform the function of the kidneys and are used for patients suffering from CKD (Chronic Kidney Disorder). An example of a safety device in this machine is the efficient design of the air bubble detector. This detector must be fully functional and should ensure that no air bubble passes to the patient's body. If this occurs, the patient may have seizures and this can prove fatal. Hence, the detector must be equipped with a proper mechanism to find out the problem, and give out beeps so that proper action can be taken immediately.
Catheter
Urinary catheter
The protective device here is the auto mechanism of deflating the balloon during procedure. If this device is not present, the balloon is deflated using peri-catheter aspiration, which provides easy access for foreign particles to enter the system.

Some other health care devices embedded with safety signals include anesthesia machines, stents, infusion pumps, centrifuge, etc.
Daily Life
Cabinet Drawer
Have you tried opening your file cabinet drawer in a hurry? You will notice that all drawers may also get opened or fall out by mistake. This is prevented using an auto-lock mechanism, which ensures that the other drawers remain locked when one of them is opened.
Kitchen Sink
The top of the sink just below the pipe has a small hole. This is a protective mechanism. It drains the water and ensures that overflow of water is prevented.
Microwave Oven
You might have observed that you cannot operate the microwave until the door is closed. Also, if you do open it, then the microwave stops immediately. Sometimes, you place a dish in the microwave and forget all about it, the microwave switches off on its own. This is called 'auto cooking mode'.
Washing Machine
A control mechanism is present in washing machines to ensure that they start functioning only after the door is closed. Also, once started, the door cannot be opened until one full cycle is complete.
Induction Cooker
Utensils made of specific metals only work on the heating plate of the induction cooker. If you use utensils that have a bottom of a different metal, it gives out a beep. Also, some work only for flat-bottomed pans. They give out a warning signal if round-bottom pots are used. One more error-detecting mechanism is that if the cooker is left in the 'on' mode for a while, it switches off on its own after some time. This prevents shocks and fires.

Some other examples in daily life include electric iron, dryer, auto-light switch, lawn mowers, electric plugs and sockets, circuit breakers, etc.
The above examples clearly demonstrate the importance of poka-yoke in various fields. It is essential to incorporate different mistake-proofing techniques, wherever possible, in order to safeguard devices and increase production. Implementing this theory will lead to eliminating a number of errors, retain flexibility, ensure authentic validation, verify syntax, etc.