What is Six Sigma?

Six Sigma is a set of practices originally developed by Motorola to systematically improve processes by eliminating defects. (A defect is defined as nonconformity of a product or service to its specifications.)

Six Sigma asserts the following:

Continuous efforts to reduce variation in process outputs is key to business success.
Manufacturing and business processes can be measured, analyzed, improved and controlled.
Succeeding at achieving sustained quality improvement requires commitment from the entire organisation, particularly from top-level management.

The core of the Six Sigma methodology is a data-driven, systematic approach to problem solving, with a focus on customer impact. Statistical tools and analysis are often useful in the process. It is a mistake, however, to view the core of the Six Sigma methodology as statistics; an acceptable Six Sigma project can be started with only rudimentary statistical tools.

Methodology

Six Sigma has two key methodologies: DMAIC and DMADV. DMAIC is used to improve an existing business process, and DMADV is used to create new product or process designs for predictable, defect-free performance.

DMAIC

The basic methodology consists of the following five steps:

Define the process improvement goals that are consistent with customer demands and enterprise strategy.
Measure the current process and collect relevant data for future comparison.
Analyse to verify relationship and causality of factors. Determine what the relationship is, and attempt to ensure that all factors have been considered.
Improve or optimise the process based upon the analysis using techniques like 'Design of Experiments'.
Control to ensure that any variances are corrected before they result in defects. Set up pilot runs to establish process capability, transition to production and thereafter continuously measure the process and institute control mechanisms.

DMADV

The basic methodology consists of the following five steps:

Define the goals of the design activity that are consistent with customer demands and enterprise strategy.
Measure and identify CTQs (critical to qualities), product capabilities, production process capability, and risk assessments.
Analyse to develop and design alternatives, create high-level design and evaluate design capability to select the best design.
Design details, optimise the design, and plan for design verification. This phase may require simulations.
Verify the design, set up pilot runs, implement production process and handover to process owners.

Some people have used DMAICR (Realise). Others contend that focusing on the financial gains realised through Six Sigma is counter-productive and that said financial gains are simply by-products of a good process improvement.

What is Lean?

Lean manufacturing or lean production, which is often known simply as 'Lean', is the optimal way of producing goods through the removal of waste and implementing flow, as oppose to batch and queue. For many, Lean is the set of 'tools' that assist in the identification and steady elimination of waste. As waste is eliminated quality improves while production time and cost is reduced. The "tools" consist of value stream mapping, 5-S, Kan-ban (pull systems), and poka-yoke (error-proofing).

What is Lean Six Sigma?

Lean Six Sigma is a business improvement methodology which combines (as the name implies) tools from both Lean Manufacturing and Six Sigma. Lean manufacturing focuses on speed and traditional Six Sigma focuses on quality. By combining the two, the result is better quality faster.

Typical application of Lean Six Sigma (simplified)

Identify the processes (in a functional department or business) most important to delivering customer value.
Map these processes using Value Stream Mapping (a Lean tool).
Identify the bottlenecks / constraints in the value stream.
Apply variation reduction through DMAIC/DMAD(O)V to standardise the relevant process steps.

Information source Wikipedia 2008