Introduction to Six Sigma

If you never sorted out parts to fulfill the specification limits. If you never lamented about too many failures, reworks and checks. If you never forced to manufacture a product outside the process capability. If you never discussed about late payments, wrong invoices, delayed shipments, too less or too many items produced. And, if you never identified a cost reduction opportunity which you could not realize, then probably you have already implemented LEAN SIX SIGMA.

Six Sigma is a company-wide management strategy for the improvement of process performance with the objective of improving quality and productivity to satisfy customer demands and reduce cost. (S.Park, Six Sigma for Quality and Productivity, APO, 2003)

It is a program aimed at the near-elimination of defects from every product, process and transaction. (R. Tompkins, GE beats 13% rise, Financial Times, 1997)

A strategic initiative to boost profitability, increase market share and improve customer satisfaction through statistical tools that can lead to breakthrough quantum gains in quality. (M.J. Harry, The Vision of Six Sigma, Tri-Star, 1998)

Therefore, Six Sigma is a gauge of quality and efficiency, and a measure of excellence. It means delivering top quality services and products while virtually eliminating all internal inefficiencies. It is a process quality goal that comes out of statistical probability measurement and process capability technique. Six Sigma organizations produce not only excellent products but maintain highly efficient production and administration systems that work effectively with company’s entire set of processes, including support, purchasing, human resources and customer service.

The term Six Sigma is taken from a letter in the Greek alphabet and is used in statistics as a measure of variation. Six Sigma Quality is a term used generally to indicate that a process is well-controlled. The term is usually associated with Motorola, which named one of its key operational initiatives “Six Sigma Quality”. (ASQ’s Online Glossary)

Sigma, as a statistical term, measures how far a given process characteristic deviates from perfection. The central idea behind Six Sigma is that if you can measure how many “defects” you have in a process, you can systematically figure out how to eliminate them and get as close to “zero defects” as possible. The statistical representation of Six Sigma describes quantitatively how a process is performing. To achieve Six Sigma, a process must not produce more than 3.4 defects per million opportunities. A Six Sigma defect is defined as anything outside of customer specifications. A Six Sigma opportunity is the total quantity of chances for a defect.

The DMAIC cycle is followed for every implementation of a Six Sigma.

D-define. Description of the project including scope, goal and boundaries. Key metrics and defined financial improvements will be used to describe the project goal. Development of a project strategy. Choosing the correct Team Leader (Green Belter) and members (Yellow Belters).

M-measure. Is an evaluation of the current process. Documentation of all results (Outputs) and all factors (Inputs). Also, the capability definition of the measurement system and the process.

A-analyze. Application of a several analyzing tools such as Cause & Effect Matrix, a FMEA, Pareto or variance analysis to evaluate the importance of each input. Should be able to narrow down the root cause/s for the defect occurrences.

I-improve. Collection, prioritizing and validation of improvement opportunities. Improvement for optimum or robustness of the process or equipment.

C-control. Implementation of effective steps to sustain the achieved improvements such as control plans, FMEA and visual diagrams. It should be associated with process review for long term stability.

Implementing Six Sigma manufacturing means more than delivering products without defects, it means eliminating almost all defects, rework and scrap. It includes operating processes under statistical control, controlling input variables, rather than inspecting for defects at the end of the process, and it means maximizing equipment uptime and optimizing cycle time.