Invest in quality, not spend on failures, troubleshooting with Six Sigma. Decide the best


I’ll start this article with a fact witnessed, some time ago, being speaker, at a quality-related Conference, and that gave me some surprise. The issue to be addressed in the Conference should be related to activities, techniques, or tools that add value and are used to upstream, in prevention, as a way to make quality. The fact to which I refer is that one of the papers dealt with inspections which are made, downstream, typically in warehouses of the customer, as protective action to the client, when a fault has been detected and you must prevent other defective products to reach the production lines. The speaker, skilled man, do not doubt me, presented his subject as a prevention activity, the insisted that even if it was at the gates of the client it was a preventive action. The truth is that I was surprised somewhat, to the presentation, but what surprised me most was the debate that was generated on these inspections. My opinion was, and is, that those actions of containment are clearly assigned to the area of failure costs since they do not add any value, are one pure economic and of image both expenditure.  There are times that confusion can take possession of a public, I want to believe that the drift toward 100% inspections in the client’s home had was caused because among the participants there were many affected by these inspection activities. In particular, we were going to talk about how do quality and we ended up talking about the things to do when it is not quality.

Since I came the first news on Six Sigma I have wondered what is the contribution of this form of management for the success, within the strategic balance which should be in the triangle quality, cost and time?. The first news related to this concept came to me at the beginning of the 1990s; at that time already had a lot of experiences in the application of statistical Control, the quality of products and processes, I began to wonder what had this form of management so that, by applying the statistical, it would be capable of outstanding successes in the quality of the company that used it. Perhaps, also, since those moments boils  within me a series of disputes over the goodness, or not, to implement the concept of Six Sigma in order to improve quality, reduce costs and times. I don’t know why but there has always been something that I was looking for another side in those reflections. In this article will try to sort out these contradictions and locate among our tangled world of those solutions which, at least for me, they are complete and simplify the processes of improvement.

We have to go back to the origin of this Motorola program, so that the basis of my arguments make sense. For the year 1987, when Motorola launches the implementation of Six Sigma program, remember that key processes now used in quality management or systems were not applied forms widespread and serious; for example a couple of years earlier had made my first study of an FMEA, and the advanced quality planning was in its infancy, represented, almost exclusively, by a planing in a paper, without more details. I believe that, as a result, knowledge and quality management were not at current levels. The QS 9000 comes out on September 1, 1994 and the ISO 9000 were in their first drafts. As I see it, and not to dwell, the quality tools, as we know them today, did not have the level of dissemination and application which today, year 2015, have.

On the other hand, and although the time has passed and the knowledge has been extended, I also have to say that from experience recent in today, many companies apply these tools by obligation, under pressure from customers and standards being all in simple wet paper, not useful at all, which makes go leaving aside from good practice without impact on the launch of new quality products.

Unextended me more, with the situation of those times, I reach the conclusion that the quality of the products was based, in large part, on the experience of the actors involved and in the improvement after the launch, and, in many cases, leaving in hand the final customer claims rise as a source of improvement. In those moments I used to say that we were able to leave the final control in the client’s home. Then, and today, it was also fashion welcome considering claims for improvements. I of course do not say that this is wrong, but I believe more correct not to engage in incidents which always cost more than not having them. According to this, it was necessary to have a system for resolving problem such as Six Sigma.

f I turn back a little more, in the history of the statistical process Control, find a resemblance with the concept of six sigma; Dr. Shewhart about 50 years before recommended establishing limits of notice in the processes required to take corrective actions when a product reached a value between the warning limit and tolerance, until it began to not comply with the specifications.

Ultimately the 6 Sigma seeks the process to be a 3 sigma security separation between the lower limit of the specification or tolerance (LST) and the natural lower limit (LIN), and between the upper limit of the specification or tolerance (LST) and the natural upper limit (LSN) another 3.0 sigma clearance, to prevent the emergence of off-specification products (I call natural limits to those located at ±3 sigma the average). These clearances consider them levels of safety in order to prevent the occurrence of defective parts if the average creeps to any limits or variation (sigma) increases. The base and difficulty of the method is that a process that they have set a tolerance and does not meet them, meet them after you applied the defined in the six sigma DMAIC process.  Everyone will agree that this is a reactive action, which costs time and money and, in addition, I’m not sure that the work to be performed on the process let optimized and if leave it: the new field of natural tolerances is 50% of the tolerance of the specification field?


As I said, a couple of paragraphs, it seems to me that this concept is very similar to the one presented by the Dr. Shewhart, when in his book «Statistical Methods» was talking about the possibility of establishing  warning limits in the process, in order to ensure the non-appearance of parts out of specification. Specifically, in a process that is optimized and accepted, under statistical control, know, as a result, the estimate of the standard deviation, the average value and it must be in the nominal value of the specification, or very close. To be sure that you do not go out off-specification products placed, to control the operation of the processes, warning limits  inside the specification limits.


A moment ago I just say that between these two concepts there is some similitude, really, only some resemblance. I stress this because in my opinion the difference is enormous; in Six Sigma we have tolerances or specifications that meet, a process that does not meet them and the mission is to make that process 6σ will become 50% of the tolerance field and, in addition, that the media is uniquely close to the nominal value. In the case of the limits of notice, the situation is the opposite, we have a process under control statistical and accepted (can be under statistical control and not be acceptable) in which do not appear defective parts put warnings on the ±3σ of the process and establish tolerances in the ±6σ, or where they consider more useful. It is easy to realize that the approach of the 6σ is completely reactive and that limits notice is proactive. In other words the first model 6σ is a typical problem-solving process and as such (although savings allocated) expenditure incurred and the second invests in preventing the occurrence of failures, circumstance is that, unfortunately for this preventive action, does not get the merit of achieving savings, and is therefore not awarded with distinction and will not appear on the podium of the savers , are curious, really?

It is amazing to read how such and which company has saved a lot of money with the application of a model of problem solving, in this case the 6σ. It is certain that they’ve saved amounts advertised and that the system worked, but if I were the President of that company would think it me twice since what really remains in evidence, with such news, is that the models that were to launch their products in the market have been inefficient and ineffective and have left to escape down the drain large amounts of resources , until they were able to find a plug that closed the leak. I think that today, with the knowledge and techniques that are available to us, we cannot manage a company relying on retroactivity; There are no that put plugs in the sump should prevent the occurrence of incidents in the design of the product and the process. As at the meeting to which I referred in the first paragraph, the confusion on what implementing arises from the need to eliminate incidents that have escaped our control, this brings us to that rather than face very rigorously to preventive methods, we ended up talking about how to make 100% inspection in customer warehouses, regrettable.

At first sight coup and, probably, the implementation of a structure as the 6σ beset by the need to improve products and processes seems logical. Implementation to bring, as a result, the reduction of internal failures and external costs. But we must also consider that the implementation of the system is not free, requires a more or less formal structure and, in addition, a training of the actors, who will take part in the process. Speaking of training, certainly seems interesting to note that several of the contents of the training programs on this technique are based, basically, in the application of statistics to the solution of problems, this which I think is good, but not necessary, since solving the first ingredient is knowledge deep characteristics and parameters of a product or process that have the problem , and this can not be taught from outside the affected environment.

I have spoken from the economic point of view, but from the strategic point of view I see a program 6σ as a decision in the short term. Analysis SWOT, that precede the establishment of objectives you should find, under the weakness, the cost by failure and incidents, in consequence, the recommended strategic action to fight and annul this force cannot be the 6σ if not, rather, strengthen the launch of products. So you have to do that the phases of the APQP are very solid, perfectly made and using all the resources that the current knowledge puts at our disposal for launching products and processes that are robust to variation.

Well, said, now reader is your time, if it deems it appropriate, think of what has been written, make a good and real SWOT of your system and, then, only then, decides to launch a 6S or investing waters high in the development of the system, or both. Already knows my opinion: employ the resources to invest in prevention and don’t spend them correcting failures, prevent to appear, it seems to me the best to maintain the strategic balance, for the success of the triangle quality, cost and time.