Six Sigma

Introduction

Six Sigma is a set of techniques and tools for process improvement. It was introduced by American engineer Bill Smith while working at Motorola in 1986. A six sigma process is one in which 99.99966% of all opportunities to produce some feature of a part are statistically expected to be free of defects.

History

Bill Smith, a reliability engineer at Motorola, is credited with the origination of Six Sigma. The methodology was first published in a 1986 paper by Bill Smith and Mikel Harry. Motorola declared Six Sigma as a company-wide initiative in 1995.

Methodology

Six Sigma projects follow two project methodologies inspired by Deming's Plan-Do-Check-Act Cycle. These methodologies, composed of five phases each, bear the acronyms DMAIC and DMADV.

DMAIC

DMAIC is used for projects aimed at improving an existing business process. The DMAIC project methodology has five phases:

Define the system, the voice of the customer and their requirements, and the project goals, specifically.
Measure key aspects of the current process and collect relevant data.
Analyze the data to investigate and verify cause-and-effect relationships. Determine what the relationships are, and attempt to ensure that all factors have been considered.
Improve or optimize the current process based upon data analysis using techniques such as design of experiments, poka yoke or mistake proofing, and standard work to create a new, future state process.
Control the future state process to ensure that any deviations from the target are corrected before they result in defects. Implement control systems such as statistical process control, production boards, visual workplaces, and continuously monitor the process.

DMADV

DMADV is used for projects aimed at creating new product or process designs. The DMADV project methodology, also known as DFSS ("Design For Six Sigma"), includes five phases:

Define design goals that are consistent with customer demands and the enterprise strategy.
Measure and identify CTQs (characteristics that are Critical To Quality), product capabilities, production process capability, and risks.
Analyze to develop and design alternatives, create a high-level design and evaluate design capability to select the best design.
Design details, optimize the design, and plan for design verification. This phase may require simulations.
Verify the design, set up pilot runs, implement the production process and hand it over to the process owner(s).

Roles and responsibilities

Six Sigma identifies several key roles for its successful implementation.

Executive Leadership

Includes the CEO and other members of top management. They are responsible for setting up a vision for Six Sigma implementation. They also empower the other role holders with the freedom and resources to explore new ideas for breakthrough improvements.

Champions

Take responsibility for Six Sigma implementation across the organization in an integrated manner. The Executive Leadership draws them from upper management. Champions also act as mentors to Black Belts.

Master Black Belts

Identified by champions, act as in-house coaches on Six Sigma. They devote 100% of their time to Six Sigma. They assist champions and guide Black Belts and Green Belts. Apart from statistical tasks, they spend their time on ensuring consistent application of Six Sigma across various functions and departments.

Black Belts

Operate under Master Black Belts to apply Six Sigma methodology to specific projects. They devote 100% of their time to Six Sigma. They primarily focus on Six Sigma project execution and special leadership with special tasks, whereas Champions and Master Black Belts focus on identifying projects/functions for Six Sigma.

Green Belts

Are the employees who take up Six Sigma implementation along with their other job responsibilities, operating under the guidance of Black Belts.

Criticisms and controversies

Like any other business improvement methodology, Six Sigma has been criticized for various reasons. Some critics argue that it is nothing more than statistical quality control repackaged with a new name. Others argue that it is too rigid and does not allow for creativity and innovation. Some also argue that it is too focused on defect reduction and does not sufficiently consider other business objectives.