Six Sigma is a quality improvement approach created in early 1980s. Thanks to the efforts of engineer, Bill Smith, working in Motorola in the 80s, this approach has found its way into mainstream business. Today, it has become one of the most common methodological practices used to improve business processes, product quality, enhance customer satisfaction and increase overall profitability. Over the years, although the Six Sigma approach has been refined, the goal has remained the same: to improve business processes by eliminating the causes of errors leading to defects in a service or a product.
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To accomplish this, a combination of management philosophy, a set of statistical tools and a problem-solving approach must be employed to eliminate errors and provide systems. People who work with Six Sigma practices work at different levels of accomplishment: Six Sigma Yellow Belt Certification, Green Belt Certification, Black Belt Certification, and Master Black Belt.
The Six Sigma methodology was based on the bell curve created by Carl Frederick Grauss in the 19th century. In the 1920s, a founder member of the Institute of Mathematical Statistics, statistician Cark Shewhart, showed that the process had deviated from the mean by 3 sigmas and had to be corrected. Fast forward to the 1970s, Art Sundry, Senior Executive at Motorola, complained that there was a lack of consistent quality products in the company. Bill Smith responded to the complaint by implementing the six sigma methodology in 1986. Over time, other management improvement strategies influenced the system like Zero Defects and Total Quality Management.
In this article, we discuss the DMAIC framework and provide an overview of the steps in each phase and the tools that can be used in each phase.
The DMAIC framework
To improve business processes systematically, the DMAIC framework can be used. DMAIC is a data-driven and effective five-step approach that works on eliminating expensive variation from the manufacturing and business processes. It stands for Define, Measure, Analyze, Improve, and Control. This methodology was designed for delivering the best performance without any defects and with competitive quality costs.
Let us discuss the five phases of DMAIC:
This is the first step in which we identify the customers, internal and external deliverables of the customer and the goal of the project will be defined. The primary focus of this phase is selecting high-impact projects and metrics that will be reflecting the success of the project. During this phase, questions like who the targeted customers are, what their requirements regarding products and services are, and what their expectations are, are asked. Also, the boundaries of the project are defined. Along with this the start and stop points, as well as the process flow, need to be mapped out during this phase.
Steps in the Define phase
- Defining Customers and requirements (CTQs)
- Defining resources
- Developing a high-level process map
- Developing milestones and project plan
- Developing problem statement, benefits and goals
- Prepare a project charter
- Evaluating key organization support
- Identifying team, process owner, and champion
Tools that can be used in the Define phase
- CTQ Definitions
- DMAIC Work Breakdown Structure
- Process Flowchart
- Project Charter
- SIPOC Diagram
- RACI Diagram
- Stakeholder Analysis
- Voice of the Customer gathering
This is the second phase of the DMAIC where the current process must be documented. This also includes validating the forms of measurement and assessment of the performance of the baseline. This step is similar for determining shortfall by using a customer survey. In this phase, we collect data from different sources for determining the type of defects and metrics. The most important tools that can be used in this phase are basic Pareto charts, process capability measurement, Gage R & R, and process flowcharts.
Steps in the Measure phase
- Developing data collection plan
- Collecting the data
- Beginning Developing y = f(x) relationship
- Defining unit, opportunity, and defect
- Detailing the process map of different, appropriate areas
- Determining sigma baseline and process capability
- Validating the measurement system
Tools that can be used in the Measure phase
- Data Collection Plan/Example
- Measurement System Analysis
- Process Flowchart & Value Stream Map
- Process Sigma Calculation
- Voice of the Customer Gathering
The primary focus of the Analyze phase is the filtration of the topmost causes of the Critical-to-Quality Characteristic or the CTC metric for examination. Usually, for being successful, there should not be more than three causes that require control. If there are more than three causes, it means that the isolation of the critical causes was not done properly. The other reason behind this can be that the project’s goal is way too ambitious. In this step, you will have to identify if there is any gap present between the goal performance and the current performance. Sources of variation and opportunities for priority improvement needs to be identified as well. There are several tools that can be used for this phase including scatter diagrams, hypothesis testing, multi-vari analysis, time series plots, fishbone diagrams, histograms, and Pareto charts.
Steps in the Analyze phase
- Defining performance objectives
- Determining important few x’s and y=f(x) relationship
- Identifying value as well as non-value added process steps
- Identifying sources of variation
- Determining root causes
- Prioritize the root causes
Tools that can be used in the Analyze phase
- 5 Whys
- Cause and Effect
- Fishbone Diagram
- Hypothesis Testing
- Non-Normal Data Analysis
- Pareto Chart
- Process Map Analysis and Review
- Regression Analysis
- Run Chart
- Scatter Plot
- Statistical Analysis
- Time Series
This is the fourth step of the DMAIC framework that ensures an understanding of all the causes that were identified in the Analyze phase. The aim of this phase is eliminating and controlling the causes for achieving the required breakthrough performance. Now, discipline and technology are used for designing creative and innovative solutions that will be fixing as well as preventing problems. You will also have to develop and deploy an implementation plan. For this phase, you can use tools like Hypothesis Testing, Regression Analysis, Design of Experiments (DOE), and Analysis of Variance (ANOVA).
Steps in the Improve phase
- Assessing potential solution’s failure modes
- Correcting or re-evaluating potential solutions
- Defining the potential system’s operational tolerances
- Developing potential solutions
- Performing design experiments
- Validating potential improvements through pilot studies
Tools that can be used in the Improve phase
- 5 S
- Design of Experiments
- Failure Modes and Effects Analysis
- House of Quality
- Mistake Proofing
- Pugh Matrix
- Simulation Software
In this last phase, you have to ensure that all the improvements that were made must be controlled for ensuring sustained changes and lasting results. In the case of best controls, there will be a need for little to no monitoring such as irreversible product changes and process design. But there are always some process setting, setup procedures, or some other improvements that will make the daily operation and monitoring requirements necessary. Steps need to be taken for ensuring that the process doesn’t revert to the old way.
Steps in the Control phase
- Communicating to business
- Closing project and finalizing documentation
- Defining and validating control system and monitoring
- Determining process capability
- Developing handoff to process owner and transfer plan
- Developing procedures and standards
- Implementing statistical process control
- Verifying cost savings/avoidance, benefits, and profit growth
Tools that can be used in the Control hase
- Control Charts
- Control Plan
- Cost Savings Calculations
- Process Sigma Calculation
Each of the five DMAIC phases come together in the implementation of six sigma, which can turn the business around for any organization.
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Implementation of DMAIC
In this section, we will take a look at two examples of DMAIC implementation that use varied continuous improvement models for specific applications:
Floor yield improvement in a manufacturing shop
The first example is of a repetitive manufacturing process, where the yield is increased by making products:
- Define: Identify the product flow, the specific products, and the goal
- Measure: Define the metrics that will be used as the first-pass yield, rolled first-pass yield, or OTIFNE; it will also include monitoring for time to gather baseline data that is statistically meaningful.
- Analyze: Look for trends, assess the standard deviation and mean from data, address, and identify outliers; this also includes identifying variables impacting the yield using root cause analyses.
- Improve: Define and put in place countermeasures o address the identified root causes; monitor the process to confirm the achievement of desired yield improvement.
- Control: Implement measures to maintain improved performance.
Impact on Hospital outcomes through evidence-based care
The second example shows how improvements can be driven in a hospital through observation and usage of principles of Lean in a DMAIC framework:
- Define: Ask questions like how often infections occur in a hospital, over what time frame will infection’s treatments will improve.
- Measure: Measuring the current state
- Analyze: Determine the root cause like the procedures introducing contamination and specific process steps.
- Improve: Implement a checklist like basic hygiene steps, sterile barriers, disinfectants, enhancing equipment, and avoiding susceptible areas.
- Control: Incorporate reinforcement and training to internalize the process and improve the culture; this can also include empowerment of nursing staff to ensure enforcement of the measures introduced.
According to the six sigma level, only 3.4 defects out of one million products or services are acceptable. To achieve this, continuous efforts are made to the point where predictable results and stable products are achieved.
As discussed above, the six sigma methodology deconstructs the process of manufacturing to its smallest, essential parts. It then works on defining and evaluating every step of the process and searches for ways to improve efficiencies in the structure of the business. This is done to both improve the process quality and increase the bottom-line profit.
With a good overview of the DMAIC framework, you can now work towards becoming proficient in the six sigma methodology. Start with the Yellow Belt or move up the Green Belt and Black Belt to the Master Black Belt.