learn and understand Lean and Six Sigma (part II).
2. What is Sigma (σ)? And why “six”?
3. What is DMAIC?
Six sigma is a highly structured process that focuses on developing and delivering products and services with zero errors (near-perfect).
“Six sigma has forever changed GE (General Electric). Everyone is a true believer in Six Sigma, the way this company works now”. (John F. Welch, Former GE Chairman)
This series consists of 3 articles, organized as follows:
Part 1: The Lean Process (Eliminate Waste)
Part 2: Six Sigma (Eliminate Variation)
Part 3: Lean Six Sigma Challenge (Win a free copy of the 3D Business Analyst book)
What is Sigma (σ)? And why “six” sigma (6σ)?
Sigma is a statistical term that represents the standard deviation of a process about its mean. Standard deviation is used to measure how widely spread the data values are compared to the mean. If standard deviation (σ) is zero, this means that all data values are equal and there is no error (no variation) in the process. This is the ideal case.
Sigma (σ) is a measure of variation for process performance
It provides information about the amount of variation in a process
You apply the sigma level that is appropriate to your process. Of course 6σ is the safest choice, but has a huge cost impact to move from one sigma level to a higher one. An average company applies 3σ process.
The 5 steps of the six sigma process are described as DMAIC.
DMAIC is a structured problem-solving framework widely used in six sigma process. It consists of five phases: Define, Measure, Analyze, Improve, and Control.
DMAIC framework supports creative thinking within the system boundaries, i.e., keeps basic processes, products or services. It does not start a new system from scratch
3.1. Define (customer & goals to understand problem)
Process Improvement projects start with a need or a goal to be achieved. In the define phase, team members get introduced to the project, their roles and what they are trying to achieve.
The define phase in DMAIC is very similar in concept to the initiation phase in project management.
Tools and tasks performed in define stage:
– Define the project goals – why are you doing the project?
– Create the project charter – what is the problem, goals, scope, schedule, impact, and team?
– Develop the team and launch the project
– Define the customer
– Define value from customer’s perspective, “Voice Of Customer” (Lean & Six Sigma integration)
– Develop SIPOC Diagram
3.2. Measure (where are we now?)
The work you have done in the Define stage is to understand the process required to improve its performance and identify the customer goals. In the Measure stage you need to clarify things by investigating how and how well the work gets done. The purpose is to establish the current performance level (baseline) and collect data about the process to be analyzed in the next stage. Tools and tasks performed in the Measure stage:
– Walk the process
– Collect baseline data
– Create current state map (read more in part 1)
– Identify problems and opportunities
– Other statistical tools
3.3. Analyze (understand why problems occur)
Now that you know what is happening in your process, it is time to find out why and identify the potential root causes of the problem, which you will work on resolving and improving in the next stage.
Root-cause analysis (Fish-bone diagram) and 5 Whys technique are the most common tools used to push the team beyond symptoms to uncover potential root causes.
Both Measure and Analyze stages involve a good amount of advanced tools that require more in-depth knowledge of statistical principles which will not be covered in this article, as this is an introduction to Lean Six Sigma. However, here are the common tools used to measure and analyze the process performance for your further readings. You can read more about these tools in the Six Sigma Vocabulary section:
– Measurement System Analysis
– System Capabilities Cр & Cрк
– Regression Analysis
– Failure Modes & Effects Analysis (FMEA)
– Control Charts
– Hypothesis Testing
– 5S Technique – see the 6σ vocabulary section
– Theory Of Constraints (TOC)
– Analysis Of Variance (ANOVA)
– Time Value Analysis
3.4. Improve (Solve problems)
At this point, you have defined your customers and their goals/problems, measured your process to understand its current state, and performed further analysison the system to identify the root causes of the process problems. Now it is time to brainstorm with the team to come up with some ideas to address the root causes, select the best ones and implement them to improve the process.
Tools and tasks performed in the Improve stage:
Develop the ideal state map (Lean & Six Sigma integration)
Use Lean principles (FLOW & PULL) to eliminate waste (Lean & Six Sigma integration)
Brainstorm improvement ideas
Prioritize and select improvement ideas by using PICK Chart
Develop Future State Maps (Lean & Six Sigma integration)
Design Of Experiments (DOE)
3.5. Control (sustain achievements)
In this stage you need to control the process to make sure to sustain what you have achieved in process improvements. Putting a control plan in place is crucial to ensure that the process is carried out consistently and it does not go back to its initial state before improvements. Also controlling the process will result in early detection of any defects that could occur later on.
Tools and tasks performed in the Control stage:
– Measurement System Analysis (MSA): it is the process of validating and calibrating the measurement system for its accuracy, — – sensitivity and precision
– Control Chart: it is a time plot chart showing process performance, mean (average) and control limits. It is used to determine if – the process is in control (within control limits) or not
– Communication Plan
– Target Progress Report
– Sustainment Plan
– Transitioning the project to the customer and closing it