Poka-Yoke for Zero Error
19 May 2015 07:05 am
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Poka-Yoke is a Japane
se term which effectively means “mistake proofing”.
The common term we are familiar with is “fool proofing”, but this does not fit in with the Japanese understanding of the concept of Poka-Yoke, and hence the equivalent term “mistake-proofing”.
In our country we have a tendency to tolerate mistakes, and even believe that it is human to make mistakes. Most believe that as long as there are human interventions in work there will be mistakes.
"A zero defect culture is one that has to be built in every organisation and throughout the country"
Mistakes can be disastrous
In my early days and working at the Peliyagoda unit of the State Engineering Corporation, I used to be fascinated by the dredger which was dredging the Kelani River and pumping out sand to the then Northern Approaches Highway project.
One day, the familiar sight was gone, the dredger had sunk. A worker had mistakenly opened the wrong valve, the floating tanks were flooded, and it was underwater in a flash. Many months of hard work went into rescuing it and was back in operation. It didn’t take too long for it to go down for the second time for the same reason. No lessons learnt. No action to mistake-proof the possible carelessness of the worker.
Mistakes could be fatal. An elderly gentleman who used to play tennis with me was given some acid by a pharmacy by mistake instead of a laxativewhich he had asked for, and he was seriously ill. The police, who initially thought it was attempted suicide, found the pharmacy store was extremely disorganised with very poor identification labels. A careless error due to the absence of visual management.
At the junction near my residence controlled by traffic lights there are often conflicts between motorists. The reason is that at many junctions in Colombo a green light without an arrow indicates that you can either go straight or turn right, but at this junction you cannot turn right but who knows. Ambiguity causes this problem and I have noticed near misses and near fisticuffs many times. You need an unambiguous visual indication here.
" Today we talk of achieving a six sigma level of quality (or accuracy) and that means that you could only have a maximum 3.4 defects (or instances) per million pieces (or instances)"
Getting it 100% right
Although it was the Americans who first initiated the zero defect movement it was the Japanese who perfected it. Aiming at 100 percent right is a concept that almost all Japanese believe in, because it has been drilled into them from childhood.
Many people accept a certain percentage of defects but in most Japanese organisations they would only tolerate a few defects per a million, certainly not one in a hundred as a percentage. Today we talk of achieving a six sigma level of quality (or accuracy) and that means that you could only have a maximum 3.4 defects (or instances) per million pieces (or instances). That is what is meant by six sigma accuracy.
Some ridicule the concept of “getting it 100 percent right” and “getting it right the first time” saying Bill Gates and Steve Jobs never got it right the first time. We are not talking about inventions and innovation here, we are talking only about repetitive work.
A zero defect culture is one that has to be built in every organisation and throughout the country. In the 1990s when I was at the Employees’ Trust Fund Board we were discussing the need to reduce processing errors. One of my DGMs was insisting that as long as human beings do the processing, errors were inevitable. I asked him what his acceptable percentage was and the answer was that 5 percent errors were reasonable. This translated into a staggering 400 wrongly processed refund claims per month, since we processed 8,000 per month at that time. I insisted that this was not acceptable and asked him whether he would, if he ever went for surgery, inform the surgeon that 5 percent error on him would be acceptable. He immediately changed his rigid stance.
Types of errors
To systematically analyse and reduce errors it is necessary to categorise errors. Although this is usually applicable to a manufacturing facility I see no reason why it cannot be equally successful in a service environment. I have suggested to some Internal Auditors to study the merits of applying this in such an office environment as well.
Poka-Yoke categorises errors into the following ten types:
Intentional errors – These are errors caused intentionally, sometimes by a disgruntled employee in general or to get someone else punished. This is sabotage, it is a criminal act and therefore needs close surveillance and special security control in sensitive areas to prevent such errors. Many Poka-Yoke initiatives are possible here but this is the hardest to prevent. Being involved in a Management Information System for Co-operative retail stores many decades ago we introduced ratios which brought out the exceptional figures and these were places where frauds had taken place, and as a result such frauds declined significantly.
Hasty errors – These are caused by employees who have acted hastily, or who have not listened to instructions, or who have acted hastily in an emergency. This can be mitigated by longer training periods, and even taking steps to place levers, operating handles etc in such a position that hasty and incorrect operation is prevented. You cannot insert the wrong charger to your phone if you try this in haste because it will not fit. Some IT systems are designed in such a way that information has to be typed in in a particular sequence, so that you cannot skip any information in haste.
Careless errors – These are errors caused by carelessness and forgetfulness. Poka-Yoke can prevent these by further training, and ensuring that making that error is not permitted. If you carelessly forget to wear the seat belt a warning sound will alert you. If you forget to place the lever in Park position in your automatic transmission car you cannot take the key out. You cannot turn on the ignition in Drive position. In Gmail if ever you type attachment in the body of your email and do not attach a file there will be a pop up message reminding you that although you typed “attachment” you seem to have forgotten to attach it. In typing usingword processing software, the software will auto correct or underline the word or phrase to bring your attention to a misspelled word or an incorrectly structured sentence.
Casual errors – Errors made when not focusing on the activity, or being too casual. Not reading a document well and having a cursory glance only, handing over a 500 Rupee note thinking it is a 20 Rupee note, blindly moving forward following the vehicle ahead after being stopped at a traffic light without looking to see if the light has turned green, are examples of Casual Errors, and can be remedied by additional information systems.
Amateurish errors – Errors caused by unfamiliarity and lack of experience are Amateurish Errors. Examples are first time drivers on the Expressway cutting back to the normal lane too soon after overtaking a vehicle. Novice drivers pressing the accelerator instead of the brake. Training, certification, checklists and information systems are possible remedies.
Compulsive errors – Errors caused by a compulsion to defy rules or standards. Examples are errors caused by vehicles proceeding across a railway level crossing even with a warning light and a warning bell. Poka-Yoke remedies are possible to prevent even a cyclist creeping through a closed gate at a railway crossing. Going above the speed limit has electronic speed indicators that light up and indicate the speed in some countries.
Thoughtless errors – Errors caused by inattention or “dreaming” or some thought suddenly gripping your mind. These can be remedied by occasional deliberate disturbances, and bringing the person back to the present.
Timing errors – Errors caused by slow reaction or late judgement, or even by poor anticipation. This is common in novice motorists. Some vehicles have sensors that beep whenever any object is too close.
Irresponsible errors – Errors caused by a lack of responsibility. Novice homeowners not securing doors and windows when retiring for the night. Checklists and colour codes are possible remedies.
Out-of-the-Blue errors – Errors that occur just “out-of-the-blues” and you cannot figure out what went wrong. This is the most difficult type of error to remedy with Poka-Yoke.
Visual Management
Visual management is a set of methods to use shape, size, and colour to prevent errors. The best example of visual management is in team sports where the two teams wear different coloured clothes, and have the names of the team printed.
If you switch on the TV and the picture that appears is of a cricket test match you will take a long time to figure out who the teams are and who is bowling and who is at the crease. All are in white. Not so in a limited over match, you can within seconds figure out all the details because of the coloured dresses, country and player name on the shirt. It is the same in a factory or office.
Well organised factories have colour coded pipes to indicate which carries electricity, which carries water, which carries diesel and so on. This will ensure that there will be no mix up. It is further refined in the case of gases where the cylinder as well as the pipeline has a different colour for each gas. Different oils are colour coded and so is the oiling frequency.
In offices you could use different colours for files, for different forms, for different registers etc. I have seen a hospital where they use colour coding very effectively. Infected waste bins are in one colour, while sterilised equipment and materials have another colour and so on. This hospital boasts that the visual management system had resulted in a lower mortality rate.
In factories it is much easier because you could use electronic sensors for detecting abnormalities, and many types of jigs and fixtures could be used. If one puts his mind to it, implementing a suitable Poka-Yoke mechanism is possible in every situation, but only if you first believe that a journey towards zero error is desirable and possible.
(The writer is a management consultant specialising in Productivity Improvement and Japanese Management Techniques. He was a former President of the Japan Sri Lanka Technical & Cultural Association (JASTECA) and the only Sri Lankan to be awarded the APO Regional Award for productivity promotion in the Asia Pacific region. He was the founder President of the Quality Circle Association of Sri Lanka as well as the Sri Lanka Association for the Advancement of Quality and Productivity.He can be contacted at sunil.wijesinha@gmail.com)