Production & ManufacturingQuality

Poka-Yoke error prevention

This method means using means that prevent or warn of the error. For example, the parts that are assembled may be designed so that they can only be assembled in the correct position. The screw holes for the circular shapes may be made asymmetric on the circumference of the circle, so that only one position can be assembled, which is the correct position. A well-known example is that the car door is not allowed to be closed except with the car key, which prevents the car key from being forgotten inside when leaving, as well as light warnings when the car door is not closed or the driving belt is not put on.

Among the examples related to the computer is that the computer puts a red squiggly line under each word that it deems to be spelled incorrectly, and that it asks you before closing the file whether you want to save the data or not. . This culture recognizes that human error is possible and that equipment error is possible. Therefore, we use tools that prevent or warn of error before it occurs. We are not happy with the recurrence of the error and our ability to confront it, but rather we are happy to prevent the error from occurring in the first place. In the Toyota system, the occurrence of an error means that we – as a work team – have not developed a means to warn or prevent this error.

In the Toyota system, this idea is applied to prevent error in any process, especially production processes. The simplest means are sought to achieve this purpose, which is in line with the policy of simplification in this system. This idea has been applied outside the scope of work to the field of product design so that the user cannot make a mistake. It has also been applied in the field of services because of its positive impact.

Error prevention culture is linked to the Toyota production system

This method is in line with the rest of the elements of this culture, such as solving problems from their roots, Root Cause Analysis, as we prevent the occurrence of the problem. The culture of error prevention meets the culture of the visual site because the use of visual means often aims to prevent error. When you put something visual that shows the error or warns of it, you prevent the error. The quality control circles, the team culture and the essential participation of the workers who deal with the equipment directly, all this is the main source of the ideas of error prevention. Ideas do not come from the manager or the engineer, but most of them stem from the workers on the production line, and the manager and the engineer may help in developing and implementing them. As you can see, the elements of this culture are interconnected, so that the application of the Toyota production system needs integration in applying its elements in a real way that penetrates into the thinking of the workers.

On-site applications

Use a checklist when checking equipment. The checklist is a list of a number of things to be checked, and the employee puts a tick in a small box in front of each point when it is checked. In the end he can be sure that he hasn’t forgotten anything if there is no empty square. An idea that seems trivial, but it is very impressive. Do not tell me that the worker memorizes these things and will not leave anything. Don’t you forget the routine and very important things in your life? So is it at work.

Placing a cover over or around dangerous switches such as the full stop switches of a large factory. These keys are used to stop suddenly when an error occurs, but someone may have made a mistake and pressed them for no reason. This is similar to a switch cover, which may protect children.

Designing parts so that they can only be assembled in one position, which is the correct position
Limit switches, which do not allow the machine to operate if the part is not positioned correctly, or that prevent a vehicle moving on a bar from crossing a line, or those that stop the machine if an error occurs and a part collides with this switch, and so on.

The use of electrical switches that lights a lamp if the water or liquid level in a tank reaches a low or high level
Using an electronic counter to ensure that the correct number of holes or cuts has been made
Use standard work specifications and put them in the workplace. This prevents steps from being forgotten or neglected

Any gauges such as gauges of pressure, temperature, length or weight that are used to warn of an error or to stop the machine if the gauge reaches an inappropriate value
Placing a colored mark on the screw and nut when assembling them so that the worker can see by sight if there is a relative movement between them, i.e. the beginning of the dissolution (unscrewing) of the nut
Putting colored markings when disassembling the exact parts so that they are assembled in the same position

Clarify the permissible measurement range on the measurement meters using colors
Clarifying safe paths and exit places in the workplace clearly
The use of industrial safety and protection tools such as a helmet, safety shoes and safety belts, depending on the nature of the work

Place the required number -only- of nails to assemble each part next to the worker in a small container so that if any nail remains after assembly, this means that a nail has not been installed. And so on any small parts that can be forgotten to fit

The validation process that takes place in information systems, in the sense that the system gives a warning when entering a number that appears to be incorrect, or does not accept the entry of numbers that are certain to be incorrect.

Store semi-finished products in tanks or spaces that can only hold a specific number of product
Putting a colored or legible mark on the storage tank or box so that if the stock reaches this mark, the worker knows that he has to re-order this material or tools
applications in other fields

My colleague told me about a train he rode in Japan years ago, and the train traveled 900 km, and the passenger could charge his car with him on the train. The passenger cuts a ticket to charge the car, then goes to the place where the car is loaded, and his car is lifted on a shelf that has the same color as the ticket. When the train arrives at any station, no error can occur because the colors of the racks are a sign of the car’s arrival station. This is a direct application of visual means of error prevention, and this is the spirit of this idea, which uses methods that are simple, inexpensive and at the same time successful and accurate
Automated teller machines that sound a warning if you leave your card or money in the machine

Drawing sequential steps on the floors of museums or places of services to determine the appropriate path for the customer or visitor
Uses of photovoltaic cells in elevators to prevent the elevator from moving if someone is close to the wall or door

How do we apply it?

Are we going to transfer and apply these examples? Are we going to put a lot of paintings in the factory and use a lot of color? The culture of error prevention and visual location begins with the manager’s conviction of this and his employees and supervisors. And then everyone starts looking for errors and putting in place measures to prevent them from happening. These procedures should be as simple as possible and stem mainly from the workers. Applying this matter in a formal manner devoid of honesty will not bear fruit. This is something that you will not apply today and tomorrow and forget about the day after tomorrow. Rather, this is a culture that you follow for life, as development does not end. When you see a problem at work, look for the preventive measure and do not be happy once the malfunction is fixed. Go to the job site and stand there for half an hour and see what goes wrong or could go wrong. Discuss with the staff and ask them to suggest ways to prevent these errors. Try this method, you may find it interesting.


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