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LEAN SIX SIGMA PRINCIPLES

When quality control becomes an unnecessary preoccupation

To become World Class, each manufacturer needs to combine error free production with higher productivity. To achieve both these things, Six Sigma and Lean Manufacturing principles need to be implemented in their organizations simultaneously. Six Sigma and Lean Manufacturing are different strategies, first focuses on variation and its reduction and other focuses on productivity. So, if we combine both a new concept was emerged known as Lean Six Sigma.

Michael George (1) defines the principles of Lean Six Sigma as:

The activities that causes the customer’s critical-to-quality issues and create the longest time delays in any process offer the greatest opportunity for improvement in cost, quality, capital and lead time

Bill Carreira (2) on the other hand defines the concept as

Lean Six Sigma is about relentless, sustained improvement – analysis after analysis, metric after metric, and project after project- lean causes products to move through processes faster, and Six Sigma improves quality.

Six Sigma

Six Sigma (6Σ) is a business strategy that fine-tunes processes to almost zero-degree of error tolerance as a way to reduce waste, defects and irregularities in both products and services.

In statistical parlance, 6 Σ is the “nickname” of six standard deviations from the mean—which numerically translates to about two (2) defects per billion. In layman’s language, a particular manufacturing process cannot go beyond producing two (2) defects per billion parts produced. Six Sigma is, therefore, achieved only if defects are kept to an almost perfect production rate equivalent to 99.9997%. In other words, the widely used failure rate of 3.4 parts per million is already an unacceptable mathematical figure—which in reality corresponds to roughly 4.5 sigmas. (Use the Sigma Level/ DPMO calculator to compare sigma level with or without this 1.5 shift)

Since Six Sigma focuses on process quality, it is imperative to measure how many defects are in a process and thereby figure out how to systematically eliminate errors—adopt fine-tuning methods—and achieve concrete and measurable results which is close to being perfect.

Once the level of 6Σ excellence and consistency is realized, quality control normally is no longer necessary.

Can Lean Six Sigma do it right?

Perhaps the question should be: How important is Six Sigma?

Majority of companies around the globe typically operate at about 4-sigma precision—or nearly 99% perfection.

The Six Sigma way is to understand the customers’ needs, gather valuable information and data from the processes, and make accurate statistical analysis from it to improve the processes.

At the end of the day, making it to the 6Σ level is learning from the mistakes and successful process deployments in the past, and getting the required support from co-workers and the valuable backing of top management.

If companies are able to make 6Σ take place in their respective backyards, quality control becomes an unnecessary preoccupation—and companies will definitely have a happy, satisfied and growing customer base.

Tools used

Lean Six Sigma tools used are as follows:

5 Whys
5S
Affinity Diagram,
Analysis of variance (ANOVA)
Balanced Scorecards
Bottlenecks Identification
Box plots
Brainstorming
Cause & Effect Diagram
Cause and Effect Matrix
Cellular Manufacturing
Control Charts
Design of Experiment (DOE)
Failure Mode Effect Analysis (FMEA)
Force-field Analysis,
Histograms,
Hypothesis Testing (t-test (two-sided), Chi-Square test )
Kaizen
Kanban
DMAIC
Lean Six Sigma Project Charter
Linear & Multiple Regression
Measurement System Analysis (Gauge Repeatability & Reproducibility)
Measures of Central Tendency & Variation (Mean, Mode, Median, Standard Deviation, Range)
Mistake Proofing
Normal Distribution
Overall Equipment Efficiency (OEE)
Pareto Diagram
Process Capability Studies (Cp and Cpk)
Process Control Plan
Process Flow Charts
Quality function Deployment/Voice of Customer
Rapid Prototyping
Sampling & Data Collection
SIPOC Diagram
SMED
Takt Time
Total Productive Maintenance (TPM)
Value Stream Mapping
Visual Controls

Both strategies require product focus and customer focus in terms of their requirements. Both tools are improvement tools, but one should focus more on those tools, which is more relevant. If wastes are need to be minimized or productivity needs to be improved then focus on Lean and if product variation needs to be controlled, then Six Sigma must be applied.

References:

1 Lean Six Sigma : Combining Six Sigma Quality with Lean Production Speed

2 Lean Six Sigma That Works: A Powerful Action Plan for Dramatically Improving Quality, Increasing Speed, and Reducing Waste

Oskar Olofsson, 2009