Tamara Wilhite is a technical writer, industrial engineer, mother of two, and published sci-fi and horror author.
Six Sigma is a process improvement methodology focused on improving product or service quality to the point that there are no more than 3.4 failures per one million occurrences. What are the advantages of Six Sigma? And given his narrow focus on quality, what are the disadvantages of Six Sigma?
Advantages of Six Sigma
Six Sigma quality refers to having 3.4 defects per million opportunities or product samples. It is a challenge to achieve this quality standard, and meeting Six Sigma quality standards is a strong selling point for companies that achieve it.
Adopting Six Sigma process improvement puts in place a continual process improvement methodology at all levels of an organization. Once Six Sigma is embedded in a corporate culture, the business processes will continue to improve. Furthermore, new problems will be quickly identified and corrected due to the close monitoring Six Sigma entails.
By focusing on defect prevention over fixing defects, companies can realize major and continuing savings over prior rework, scrap and return costs.
Six Sigma is data driven. You can see when you're going off track as soon as the measured trend starts to hit the upper or lower control limits on the chart.
No changes are made until the current process is thoroughly understood, documented and measured. The revised process is similarly measured and verified. If the Six Sigma project does not deliver what was intended, the Six Sigma team is still there to correct new found problems or study what went wrong.
Training a few Six Sigma black belts creates a core of process improvement experts who will train green belts and yellow belts as well as new hires at all levels.
Six Sigma as a process improvement methodology allows you to chart progress over time, from improved quality standards to money saved.
When Six Sigma projects are thoroughly documented, the lessons learned from those projects is readily shared among experts and can be searched by other employees looking for ideas to improve their own sites or assembly lines.
Disadvantages of Six Sigma
Six Sigma is a quality initiative, not a targeted process to reduce costs. Dramatically improving quality may save money by eliminating defective products, costly rework and returned products. Yet the cost savings are a by-product of the process improvements to any quality improvements. Six Sigma projects may not yield any cost savings at all. Improving product quality can generate capital costs and long term overhead costs in terms of more quality personnel.
Six Sigma quality is not synonymous with lean manufacturing. Adding new quality checks, improved test equipment or better manufacturing equipment with tighter tolerances may actually increase manufacturing footprints, use more material or consume more resources. Lean Six Sigma attempts to hybridize these two concepts, but it requires far more data and analysis to compare potential projects and their outcomes.
Not all products or operations need to meet Six Sigma quality standards. Medical manufacturers and aerospace companies should meet Six Sigma quality standards because lives literally depend upon the reliability of their products. Cell phones and computers that meet Six Sigma quality standards are more reliable than the competition, but may be more expensive. Few consumers care if their pen or desk meets Six Sigma quality standards.
When your product is good enough, the Six Sigma teams in place may need to find other work to do.
When a manufacturer realizes that they need to improve a product or go out of business, implementing Six Sigma will improve product quality. Moving down the chain, they may standardize manufacturing processes. Process monitoring and data collections are put in place. As product quality improves, tighter quality standards may be adopted or the process is left as it is but closely supervised.
Yet data collection and analysis takes up time and resources; this is called the cost of quality, and the cost of achieving high quality must be balanced against other business objectives. Six Sigma green belts go back to doing their full time job while still collecting and reporting metrics. Six Sigma black belts whose product is now good enough may be left wondering what else there is to do. Offering Six Sigma expertise to suppliers is a short term solution for keeping quality experts employed and improving quality overall, but may seem an imposition by your suppliers. And if successful in improving the quality of your incoming materials and components will decrease your own team's need for quality experts.
Six Sigma does not work well with intangible results. Six Sigma projects are best for physical products that are out of specification, either too large or too small. Six Sigma projects can be applied to business processes that generate measurable outputs such as calls handled per hour or customer wait time. Six Sigma projects do not work well with goals like improving customer satisfaction or lifting employee morale.
When Six Sigma process methodology is applied to business processes such as performance reviews or processing purchase orders, the recommended solution is often called "bureaucracy busting". This can result in push-back from management afraid of losing their jobs.
Meeting Six Sigma quality standards on your own production line is made harder by incoming supplies and materials that don't meet those standards. Switching suppliers to ones with less variability is an expense, and their higher quality material may raise your costs, as well.
Tony from At the Gemba on July 12, 2012:
Tamara Toyota do not use six sigma! Six sigma is very much a western idea and not used within Japan where they still very much use the original lean ideas.
My question was why don't they use it?
Tamara Wilhite (author) from Fort Worth, Texas on July 12, 2012:
Yes, Toyota was one of the first, major adopters of Six Sigma as a process improvement process.
Tony from At the Gemba on July 12, 2012:
I hope I never receive a pacemaker from a six sigma company! That would mean about 10 missed beats each and every month!
Why don't Toyota use six sigma?
Tamara Wilhite (author) from Fort Worth, Texas on June 11, 2012:
Quality and cost savings can be opposites.
Simone Haruko Smith from San Francisco on June 11, 2012:
A fair assessment, this! You've pointed out both some advantages AND disadvantages I do not remember encountering when I first learned about Six Sigma and was told about its major benefits and drawbacks. Thanks for sharing these points!