Six Sigma ( 6? ) is a set of techniques and tools for process improvement. It was introduced by engineer Bill Smith while working at Motorola in 1986. Jack Welch made it his central business strategy at General Electric in 1995.
It seeks to improve the quality of output of a process by identifying and removing the causes of defects and minimizing variability in manufacturing and business processes. It uses a set of quality management methods, mainly empirical, statistical methods, and creates a specialized infrastructure of people within organizations who are experts in this method. Each Six Sigma project undertaken within the organization follows the sequence of specific steps and has certain target values, for example: reducing process cycle time, reducing pollution, reducing costs, increasing customer satisfaction, and increasing profits.
The term Six Sigma (capitalized because it was written as it was registered as Motorola's trademark on December 28, 1993) derives from the terminology associated with manufacturing process statistics modeling. The maturity of the manufacturing process can be explained by the sigma rating indicating the result or percentage of defect-free products it produces. The six sigma process is a process whereby 99.99966% of all opportunities to produce some features of a part are statistically expected to be free of defects (3.4 feature defects per million opportunities). Motorola set the goal of "six sigma" for all its production.
Video Six Sigma
Doctrine
The Six Sigma Doctrine asserts:
- Continued efforts to achieve stable and predictable process results (eg by reducing process variation) are critical to business success.
- The manufacturing and business processes have characteristics that can be determined, measured, analyzed, enhanced, and controlled.
- Achieving continuous quality improvement requires commitment from all organizations, especially from top management.
The features that distinguish Six Sigma from previous quality improvement initiatives include:
- A clear focus on achieving measurable and quantifiable financial results from any Six Sigma project.
- Increased emphasis on leadership and strong and vibrant management support.
- A clear commitment to making decisions based on verifiable data and statistical methods, rather than assumptions and guesses.
The term "six sigma" comes from statistics and is used in statistical quality control, which evaluates process capability. Initially, this refers to the ability of the manufacturing process to produce a very high proportion of output in the specification. Processes that operate with "six sigma quality" over the short term are assumed to produce long-term disability rates below 3.4 defects per million opportunities (DPMO). The 3.4 dpmo is based on a "shift" of the /- 1.5 sigma created by psychologist Dr. Mikel Harry. He created this number based on tolerance at the height of the disk heap. The implicit goal of Six Sigma is to improve all processes, but not at the 3.4 DPMO level. Organizations need to determine the appropriate sigma levels for each of their most important processes and strive to achieve them. As a result of this objective, it is the organization's management task to prioritize the improvement field.
"Six Sigma" was registered on June 11, 1991 as US. Services Mark 1,647,704 . In 2005, Motorola linked more than US $ 17 billion in savings to Six Sigma.
Other early adopters of Six Sigma included Honeywell and General Electric, where Jack Welch introduced the method. In the late 1990s, about two-thirds of Fortune 500 organizations have initiated Six Sigma initiatives with the goal of reducing costs and improving quality.
In recent years, some practitioners have combined the idea of ​​Six Sigma with lean manufacturing to create a methodology called Lean Six Sigma. The Lean Six Sigma methodology looks at lean manufacturing, which addresses the flow of waste processes and problems, and Six Sigma, focusing on variety and design, as complementary disciplines aimed at promoting "business and operational excellence". Companies like GE, Accenture, Verizon, GENPACT, and IBM are using Lean Six Sigma to focus the transformation effort not only on efficiency but also on growth. It serves as a basis for innovation throughout the organization, from manufacturing and software development to sales and service delivery functions.
The International Organization for Standardization (ISO) was published in 2011 the first standard "ISO 13053: 2011" defines the Six Sigma process. Other "standards" are mostly made by universities or companies called the first party certification program for Six Sigma.
Maps Six Sigma
Differences with lean management
Lean and Six Sigma management are two concepts that share similar methodologies and tools. Both programs are influenced by Japan, but both are different programs. Lean management focuses on eliminating waste and ensuring efficiency while Six Sigma focus is eliminating defects and reducing variability.
Methodology
The DMAIC project methodology has five phases:
- D efine the system, the customer's voice and their requirements, and the project objectives, in particular.
- M the convenience key aspects of the current process and collect relevant data; Calculate Process Capability 'as is'.
- A disable data to investigate and verify a cause-and-effect relationship. Determine what the relationship is, and try to ensure that all factors have been considered. Look for the root cause of the defect under investigation.
- I mprove or optimize the current process based on data analysis using techniques such as experimental design, poka yoke or error checking, and standard work to create new, front. Prepare a test to establish the process capability.
- C ontrol future status processes to ensure that any deviation from the target is corrected before they result in defects. Implement control systems such as statistical process controls, production boards, visual workplaces, and continuously monitor the process. This process is repeated until the desired quality level is obtained.
Some organizations add an R ecognize step at the start, which is to identify the exact problem to work with, resulting in the RDMAIC methodology.
DMADV or DFSS
The DMADV project methodology, known as DFSS (" D esign F or S ix S igma") five phases:
- D efine design goals consistent with customer demand and company strategy.
- M convenience and identify CTQs (characteristics C ritikal T o Q uality), measure product capability, production process capability, and measure risk.
- A nalyze to develop and design alternatives
- D esign an upgraded alternative, most appropriate per analysis in the previous step
- V erify design, set the test run, apply the production process and leave it to the process owner.
Tools and methods of quality management
In the individual phases of the DMAIC or DMADV project, Six Sigma uses many of the existing quality management tools that are also used outside of Six Sigma. The following table shows an overview of the main methods used.
The role of implementation
One of the key innovations of Six Sigma involves the absolute "professionalization" of quality management functions. Prior to Six Sigma, quality management in practice was largely downgraded to the production floor and to statisticians in separate quality departments. The formal Six Sigma program adopts a kind of elite ranking terminology (similar to some martial arts systems, like judo) to define a hierarchy (and a special career path) that includes all business functions and levels.
Six Sigma identifies several key roles for its successful implementation.
- Executive Leadership including CEOs and other top management members. They are responsible for setting up a vision for the implementation of Six Sigma. They also empower other role-holders with the freedom and resources to explore new ideas for breakthrough improvement by overcoming departmental barriers and overcoming inherent resistance to change.
- Champions is responsible for the implementation of Six Sigma throughout the organization in an integrated way. Executive Leadership draws them from top management. Champions also act as mentors for Black Belts.
- The Black Master Belt , identified by Champions, acts as an internal Six Sigma trainer. They devote 100% of their time to Six Sigma. They helped Champions and guided the Black Belts and Green Belts. In addition to statistical assignments, they spend their time ensuring consistent implementation of Six Sigma across functions and departments.
- Black Belt operates under Master Black Belts to apply the Six Sigma methodology to specific projects. They devote 100% of their precious time to Six Sigma. They primarily focus on Six Sigma project execution and special leadership with special tasks, while Champions and Master Black Belts focus on project identification/functionality for Six Sigma.
- Green Belts are employees who take on the implementation of Six Sigma along with their other job responsibilities, operating under Black Belts guidance.
According to system advocates, special training is required for all these practitioners to ensure that they follow the methodology and use a data driven approach correctly.
Some organizations use additional belt colors, such as Yellow Belt , for employees who have basic training in Six Sigma tools and generally participate in projects and "White belt" for those who are locally trained in the concept but do not participate on the project team. "Orange belt" is also mentioned for use for special cases.
Certification
General Electric and Motorola developed the certification program as part of their Six Sigma implementation, verifying individual commands from Six Sigma methods at relevant skill levels (Green Belt, Black Belt, etc.). Following this approach, many organizations in the 1990s began offering Six Sigma certification to their employees. Criteria for the certification of the Black Belt and Black Belt vary; some companies only require participation in Six Sigma courses and projects. There is no standard certification body, and different certification services are offered by various quality associations and other providers for a fee. The American Society for Quality for example requires Black Belt applicants to pass a written exam and provide a written statement stating that they have completed two projects or one project combined with three years of practical experience in the body of knowledge.
Etymology "six sigma process"
The term "six sigma process" comes from the idea that if one has six standard deviations between the process mean and the closest specification limit, as shown in the graph, practically no item will fail to meet the specification. This is based on the method of calculation used in the study of process capability.
The study of capability measures the amount of standard deviation between the process mean and the closest specification limits in sigma units, represented by Greek letters? (sigma). As the standard deviation process rises, or the moving average moves away from the center of tolerance, the fewer standard deviations will match between the mean and the closest specification limit, decrease the sigma number and increase the probability of goods beyond the specification. We should also note that the calculation of the Sigma level for a data process does not depend on normally distributed data. In one critique of Six Sigma, practitioners using this approach spend a lot of time transforming data from abnormal to normal using transformation techniques. It should be said that the Sigma level can be determined for process data that has evidence of non-normality.
The role of sigma shift 1.5
Experience has shown that processes typically do not perform as well in the long run as they do in the short term. As a result, the amount of sigma that will fit between the process average and the limits of the nearest specification may decrease over time, compared to the initial short-term study. To explain the real-life improvements in process variations over time, a 1.5 sigma-based empirical shift was introduced into the calculations. According to this idea, a process that matches 6 sigma between the average process and the limits of the nearest specification in a short-term study would in the long run only fit 4.5 sigma - either because the process means it will move over time, or because of the standard deviation length -the behavior of the process will be greater than that observed in the short term, or both.
Therefore the widely accepted definition of the six sigma process is a process that produces 3.4 defective parts per million of opportunities (DPMO). This is based on the fact that a normally distributed process would have 3.4 parts per million beyond the limit, when the limit is six sigma from the null "original" mean and the process is then shifted by 1.5 sigma (and therefore that, the six sigma limit is no longer symmetrical about the mean). The previous six sigma distribution, when under the influence of a 1.5 sigma shift, is usually referred to as a 4.5 sigma process. The failure rate of a six sigma distribution with a mean of 1.5 sigma shift is not equivalent to a 4.5 sigma rate failure rate with a zero-centered average. This allows for the fact that a particular cause may result in a decrease in process performance over time and is designed to prevent underestimation of the degree of defects that may be encountered in real life operations.
The role of sigma shift is primarily academic. The purpose of the six sigma is to result in improved organizational performance. It is up to the organization to determine, based on customer expectations, what is the appropriate sigma level of a process. The purpose of the sigma value is as a comparison number to determine whether a process is increasing, deteriorating, stagnant or uncompetitive with others in the same business. Six sigma (3.4 DPMO) is not the goal of all processes.
Sigma Level
The table below provides the long-term DPMO values ​​that correspond to the various short-term sigma levels.
These numbers assume that the average process will shift by 1.5 sigma to the side with a critical specification limit. In other words, they assume that after the initial study determines the short-term sigma rate, the long-term value of C pk will change to 0.5 less than C pk short-term value. Thus, for example, the DPMO number given for 1 sigma assumes that long-term processing means 0.5 sigma beyond the specification limit (C pk = -0.17), rather than 1 sigma in it. , as in short-term studies (C pk = 0.33). Note that the percentage of defects shows only defects beyond the limit of the closest process specifications. Defects beyond the remote specification limits are not included in the percentages.
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Six Sigma mostly finds apps in large organizations. An important factor in the deployment of Six Sigma was GE's 1998 announcement of $ 350 million in savings thanks to Six Sigma, a figure that later grew to over $ 1 billion. According to industry consultants such as Thomas Pyzdek and John Kullmann, companies with fewer than 500 employees are less suited to the application of Six Sigma or need to adapt the standard approach to make it work for them. But Six Sigma contains a large number of tools and techniques that work well in small to medium-sized organizations. The fact that an organization is not big enough to be able to buy Black Belts does not diminish its ability to make improvements using these tools and techniques. The infrastructure described as necessary to support Six Sigma is a result of organizational size rather than the requirements of Six Sigma itself.
Although the scope of Six Sigma differs depending on where it is applied, it can successfully provide benefits for different applications.
Manufacturing
Following Motorola's first application in the late 1980s, other internationally recognized companies are currently posting high savings after implementing Six Sigma. Examples are Johnson and Johnson, with $ 600 million of reported savings, Texas Instruments, which saves more than $ 500 million as well as Telefonica de Espana, which reports $ 30 million euros in revenue in the first 10 months. On top of this, other organizations such as Sony and Boeing achieved a large percentage in waste reduction.
Engineering and construction
Although the company has considered general quality control and process improvement strategies, there is still a need for more sensible and effective methods because all the desired standards and client satisfaction are not always achieved. There is still a need for important analyzes that can control the factors that affect the cracking of concrete and slippage between concrete and steel. After conducting a case study on Tinjin Xianyi Construction Technology Co., Ltd., it was found that construction time and construction waste decreased 26.2% and 67% after adopting Six Sigma. Similarly, the application of Six Sigma is studied in one of the largest engineering and construction companies in the world: Bechtel Corporation, where after an initial investment of $ 30 million in the Six Sigma program that includes identifying and preventing rework and deformities, over $ 200 million is saved.
Financial
Six Sigma has played an important role by improving the accuracy of cash allocation to reduce bank fees, automatic payments, improve reporting accuracy, reduce documentary credit defects, reduce auditory disability collections, and reduce variations in collector performance. Two financial institutions that have reported many improvements in their operations are Bank of America and American Express. In 2004 Bank of America increased customer satisfaction by 10.4% and decreased customer problems by 24% by applying Six Sigma tools in their streamlining operations. Similarly, American Express managed to eliminate unapproved credit card renewals and improve their overall process by applying the principle of Six Sigma. This strategy is also currently being implemented by other financial institutions such as GE Capital Corp., JP Morgan Chase, and SunTrust Bank, with customer satisfaction as their primary goal.
Supply chain
In this field, it is important to ensure that the product is delivered to the client in a timely manner while maintaining high quality standards from the beginning to the end of the supply chain. By changing the schematic diagram for the supply chain, Six Sigma can ensure quality control on the product (defect free) and guarantee delivery deadlines, which are two major issues involved in the supply chain.
Health Care
This is a sector that has been perfectly compatible with this doctrine over the years due to the zero nature of tolerance for errors and the potential to reduce the medical errors involved in health care. The goal of Six Sigma in health care is broad and includes reducing equipment inventory that brings additional costs, altering the health care delivery process to make cost reimbursements more efficient and better. A study at the MD Anderson University of Texas Cancer Center, which recorded an increase in 45% non-machine inspection and a 40 minute reduction of preparation time; from 45 minutes to 5 minutes in some cases.
Criticism
Lack of originality
Joseph M. Juran's quality expert describes Six Sigma as "the basic version of quality improvement", which states that "nothing new there is what we call the facilitators, they have adopted more flamboyant terms, such as belts of color different. "I think the concept is worth separating, to create a specialist who can be very helpful. Again, that's not a new idea. The American Society for Quality has long established certificates, as for reliability engineers. "
Not enough for complex manufacturing
The quality expert Philip B. Crosby points out that the Six Sigma standard is not far enough - the customer is entitled to a defect-free product at all times. For example, under the Six Sigma standard, semiconductors that require perfect etching of millions of small circuits onto a single chip are all damaged, he says.
Role of consultant
The use of "Black Belt" as a mobile change agent has encouraged the training and certification industry. Critics argue there is a Six Sigma advantage by a large number of consulting firms, many of which claim expertise in Six Sigma when they have only a basic understanding of the tools and techniques involved or the markets or industries in which they act.
Potential negative effects
The Fortune article states that "of the 58 major companies that have announced Six Sigma programs, 91 percent have followed the S & P 500 since". The statement was attributed to "analysis by Charles Holland from Qualpro's consulting firm (which supports a competitive process of quality improvement)". The article's summary is that Six Sigma is effective on what it is meant to do, but it's "narrowly designed to improve existing processes" and does not help in "coming up with new products or disruptive technologies."
Excessive reliance on statistical tools
A more direct criticism is the "rigid" nature of Six Sigma by relying heavily on methods and tools. In many cases, more attention is given to reducing variation and looking for significant factors and little attention is given to developing toughness in the first place (which completely eliminates the need to reduce variation). The extensive dependence on significance testing and the use of multiple regression techniques increases the risk of making unknown types of error or statistical error. The possible consequence of the Six Sigma array of misconceptions-P-values ​​is a false belief that the probability of false inferences can be calculated from the data in one experiment without reference to external or reasonable evidence of the underlying mechanism. One of the most serious but overly general misuse of inferential statistics is to take a model developed through the creation of an exploratory model and test it into the same type of statistical tests used to validate predefined models.
Another comment refers to the often-mentioned Transfer Function, which seems to be the wrong theory when viewed in detail. Since the significance test was first popularized, many objections have been voiced by prominent and respected statisticians. The volume of criticism and rebuttal has filled the books with a language that is rarely used in scientific debates about a dry subject. Most of the first criticisms have been published more than 40 years ago (see Testing Statistics hypothesis § Criticism).
A criticizing article has appeared in the November-December 2006 edition of US Army Logistics on Six Sigma: "The danger of a paradigmatic orientation (in this case, technical rationality) can blind us to values related to double-loop learning and learning organizations, organizational adaptation, creativity and labor development, humanizing workplace, cultural awareness, and strategy development. "
Nassim Nicholas Taleb considers risk managers little more than "blind users" of tools and statistical methods. He stated that statistics are basically incomplete as a field because it can not predict the risk of rare events - something specifically related to Six Sigma. Furthermore, errors in prediction are likely to occur as a result of ignorance or differences between epistemic and other uncertainties. These errors are the greatest variation in time (reliability) associated failure.
Smothering creativity in a research environment
According to an article by John Dodge, editor in chief of News Design, the use of Six Sigma is inappropriate in the research environment. Dodge states "the excessive metrics, measures, measurements and intense focus of Six Sigma on reducing water variability under the discovery process." Under Six Sigma, the bulk-free nature of brainstorming and the accidental side of discovery is stalled. " He concluded "there is general agreement that freedom in basic or pure research is preferred while Six Sigma works best in additional innovations when there is expressed commercial purpose."
The BusinessWeek article says that the introduction of Six Sigma by James McNerney at 3M has the effect of paralyzing creativity and reporting its removal from the research function. It quotes two Wharton School professors who say that Six Sigma leads to additional innovation at the expense of blue sky research. This phenomenon is further explored in the Going Lean book, which illustrates a related approach known as lean dynamics and provides data to show that Ford's "6 Sigma" program does not change much of its luck.
Lack of systematic documentation
One criticism voiced by Yasar Jarrar and Andy Neely from Cranfield School for Business Performance Business Center is that while Six Sigma is a powerful approach, it too can dominate organizational culture; and they add much of the Six Sigma literature - in a remarkable way (six-sigma claims as evidence, scientifically based) - lacks academic rigor:
One final criticism, perhaps more to the Six Sigma literature than the concept, relates to the evidence of Six Sigma's success. So far, case studies documented using the Six Sigma method are presented as the strongest evidence for its success. However, looking at these documented cases, and apart from some details from leading organizational experiences such as GE and Motorola, most cases are not documented systemically or academically. In fact, the majority are case studies illustrated on the website, and the best, cryptic. They did not mention the specific Six Sigma method used to solve the problem. It has been argued that by relying on Six Sigma criteria, management is lulled into the idea that something is being done about quality, whereas any resulting improvement is unintentional (Latzko 1995). So when looking at the evidence put forward for the success of Six Sigma, mostly by consultants and people with particular interests, the question that begs to be asked is: do we make correct improvements to the Six Sigma method or just be skilled in telling stories? Everyone seems to believe that we are making real improvements, but there are ways to go documenting this empirically and clarifying causal relationships.
1.5 sigma shift
Statistical expert Donald J. Wheeler has rejected a 1.5 sigma shift as "ridiculous" because of its arbitrary nature. Its universal application is seen as dubious.
The 1.5 sigma shift is also debatable because it produces "sigma levels" that reflect short-term performance over the long run: a process that has a long-term disability rate corresponding to a 4.5 sigma performance, by the Six Sigma convention, described as "the six process sigma. " The accepted Six Sigma scoring system can not be equated with the probability of a normal distribution for a number of standard deviations, and this has been the key bone of contention about how the Six Sigma measures are defined. The fact that it is rarely explained that the "6 sigma" process will have a long-term disability rate that matches the performance of 4.5 sigma rather than the 6 sigma performance that has actually led some commentators to argue that Six Sigma is a self-confidence trick.
See also
- Design for Six Sigma
- DMAIC
- Kaizen - a philosophical focus on continuous process improvement
- Lean Six Sigma
- Lean Manufacturing
- Fashion management
- Total productive care
- Total quality management
- W. Edwards Deming
References
Further reading
Source of the article : Wikipedia
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