Some also wonder where the six sigma term that is used so often in lean manufacturing came from. The sigma is a Greek letter which is used to represent the standard deviation of a targeted population (Gupta, 2003). The six sigma term therefore comes from the idea that, if one has six standard deviations that come between the mean result of any process and the nearest limit for specification, than one will create virtually no items that actually exceed those specifications (Gupta, 2003). This idea is the main basis for what is called the process capability study, which is generally used by quality professionals, and the six sigma term has roots within that particular tool.
In summary, all management theories are very important when it comes to what is appropriate for businesses (Achanga, et al., 2006). The theory of constraints is discussed first because it is the theory that goes back the farthest, and because it is originally thought to be what created the rest of the issues that were discussed within this paper. The theory of constraints was actually the first tool that was widely used when it came to business management and quality satisfaction (Achanga, et al., 2006; Hines, Holweg, & Rich, 2004). Until that point in time, not all businesses were that concerned about the quality that they had, and even those that were concerned were not necessarily that good at being able to ensure this quality (Holweg, 2007). They did not know what they should be doing to make sure that the products that they made met the standards of quality that their customers wanted.
Some of these problems with quality came from the fact that parts and finished goods often sat around in warehouses, and this could cause these items to become damaged or not to work properly (Holweg, 2007). Even if the quality seemed to be fine when the business had made the product, the quality may have been poor when the customer finally received the product, and so the company received a reputation for having poor quality, which was unfortunate for the company that was working hard to have good quality control and provide good products (Holweg, 2007).
Because of these problems with quality, just-in-time inventory became very important, since this stopped the needed components from sitting around, and also stopped the finished goods from sitting around (Holweg, 2007). Both of these areas were important to the companies that kept having problems with quality based on the fact that their raw materials and their finished products had to sit for so long before they could be used or delivered to stores. Just-in-time planning avoided all of this and therefore became a significant part of the business life of many of the companies that used it (Emiliani, 2000).
In some ways, however, just-in-time was not really enough. It helped to improve quality and customer satisfaction, and it also helped to increase profits, but not to the extent that some companies wanted, and there were other companies that still had problems with quality control in other areas (Emiliani, 2000). Because of this, the idea of total quality management came about. This idea was created in Japan, but it was also worked on in the United States, and through a combination of work in the U.S. And migration of ideas to the U.S., total quality management was adopted by many businesses (Emiliani, 2000).
Most of these businesses were those that made parts or components, or provided products where quality control was very significant, such as electronics. By using total quality management, a company could focus on all aspects of the issue of quality, from the raw materials that were coming in to the finished product that was going out and the way that customers were handled (Emiliani, 2000). If there was a problem with a finished product, it would be repaired or replaced without hassle, and the goods that were produced by companies that used this total quality management idea were better and stronger than much of what was produced by other companies during that time period (Emiliani, 2000).
Like all management ideas, however, total quality management eventually faded away because there were other ideas appearing and other companies working to be better and better, because good quality provides higher profit, more customer satisfaction, and cost savings as well (Emiliani, 2000). It was during this time of change and discussion, when many companies were looking for something more, that lean manufacturing was born (Emiliani, 2000). This idea of six sigma that came along with that was created and trademarked by Motorola, but other companies can and do use it.
The list of companies that use it is quite long, and the companies listed previously are only a few of those that decided that this kind of quality control and operation management was important. Lean manufacturing is different based on whether a company that is already running uses it or whether it is used to create the processes for a new company, but the basic ideas are the same (Lee-Mortimer, 2006). The exception is that a new company will need their processes designed, while an already existing company will only need their existing processes changed by the lean manufacturing model.
Whether these processes need to be changed or created, however, is not the point. The main point is that the lean manufacturing idea is designed to cover everything that is involved with quality management, with the goal of seeing less than 3.4 defects per 1 million opportunities, meaning that for every 1 million parts or products produced, less than 3.4 of them should be seen to have problems (Lee-Mortimer, 2006). Usually, good quality control can even catch these defects and they will not make their way to the customer, but some of them do occasionally make it that far. When they do, the company must make things right with the customer to ensure customer satisfaction (Lee-Mortimer, 2006).
This is not always easily done, but the effort should always be made, as returns, exchanges, and other issues that involve defective products are all part of the customer satisfaction process and are significant for the company. While it is likely that something else in the future will replace the lean manufacturing idea, for now it is very important to many companies throughout this country and others.
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