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Lecture 8

Process Improvement using DMAIC

Phases of Six Sigma project

Phase 1: Selecting the project

Phase 2: Forming the team

Phase 3: Developing the project plan

Phase 4: Training the team

Phase 5: DMAIC process improvement

Phase 6: Completing the project and disbanding the team members

What is DMAIC?

D = Define the process (step 1)

M = Measure the process (step 2)

A = Analyze the process (step 3)

I = Improve the process (step 4)

C = Control the process (step 5)

Key to DMAIC success

1) Measuring the problem = using data and facts

2) Focusing on the customer = external customer

3) Verifying root cause = agree on a root cause

4) Breaking old habit = find creative new solutions

5) Managing risk = testing and perfecting solutions

6) Measuring results = verify real impact

7) Sustaining change = making sure that the change will last a long time

Step 1: Define the problem

The team must address the following questions:

  • What are we working on?
  • Why are we working on this problem?
  • Who is the customer?
  • What are the customer’s requirements?
  • How is the work currently being done?
  • What are the benefits of making the improvement?

Step 1 (cont.) - Charter of the project team

  • A business case: Why is this opportunity being chosen?
  • Problem/opportunity and goal statement: What’s the specific problem and what results will be sought?
  • Constraints/assumptions: What limitations are placed on the project?
  • Scope: What is the scope and range of the project?
  • Players and roles: Who are the team members, champion (leader), and other stakeholders?
  • Preliminary plan: When will each phase (D, M, A, I, and C) will be completed?

What should be accomplished in Define phase?

  • Problem and the business case are well defined (project charter)
  • Process has been identified
  • Stakeholders have been identified.
  • Customer requirements are established and validated using data obtained from the customer using VOC (voice of the customer) analysis.

Six Sigma tools frequently used in Define phase

  • Project charter
  • SIPOC map
  • Stakeholder analysis
  • Voice of the customer (VOC) analysis
  • Critical-to-Quality (CTQ) tree
  • Affinity diagram
  • Kano analysis

Examples of SIPOC map
(Supplier, Input, Process, Output, Customer)

What is VOC?

  • VOC = Voice of the customer
  • Sometimes the customers are not sure about what they want or have trouble expressing it.
  • Generally the customers are pretty good about describing what they don’t want.
  • Therefore the team must listen to the “voice of the customer” and translate the customer’s language into meaningful requirements.

Translate the VOC into requirements

Critical-to-Quality (CTQ) tree

Kano model of quality

What is an affinity diagram?

  • An affinity diagram is a tool for organizing discrete customer comments into a comprehensive picture of customer needs.
  • Once organized, these comments can be translated from the customer’s language into the language of the process.
  • The first step to achieve this is to drill deeper into each area of customer concern to identify the Critical-to-Quality (CTQ) requirements.
  • A CTQ tree is the tool that supports this task.

Step 2: Measure the process

  • Measure is a follow-up to step 1 (Define) as well as a bridge to the next step (Analyze).
  • Measure step has two main objectives:

1) Gather data to validate and to quantify the problems/opportunities.

2) Begin evaluating facts and numbers that offer clues about the cause of the problem.

  • Remember , Six Sigma team takes a process view and uses that view to set priorities and make appropriate decisions about the course of action.

Three main categories of the Measure step

1) Input: This is the information coming into the process for change into the output. Bad input information can create bad output information. The Measure input should evaluate all the information and identify root cause of the problem.

2) Process: This category focuses on the items which can be tracked and measured. It helps the team start to pinpoint causes of the problem.

3) Output: This is the end result of the process. It focuses on the immediate results such as deliveries, defects, complaints etc. and their impact on the long term items such as profits, customer satisfaction etc.

Type and examples of Measure step

There are many ways to measure performance at each step

Input-Output relationship

  • In Six Sigma talk, two letters “Y” and “X” are used to represent the kinds of measure.
  • “Y” stands for results and outcomes of the process. It also represents a goal or objective of the project, for example, cycle time, profit margin, etc.
  • “Y” generally links to customer requirements.
  • “X” stands for the measure that comes from input of the process, such as cost of raw material, length of phone calls etc.
  • The relationship between input and output is represented by the equation Y = f(X)

Action plan for Measure step

  • Once it has been determined what to measure, the team forms a “data collection plan”.
  • In this step the team moves from the conference room to the real world of collecting data.
  • This step involves getting the cooperation from customers, employees, and suppliers.
  • In fact many people’s first exposure to Six Sigma project is being asked to collect data.
  • A common milestone in this step is to develop an initial “sigma level” of the current process.

What should be accomplished in Measure step?

  • Metrics have been identified and defined
  • Data has been collected
  • Measurement system has been validated using Gage R&R method
  • Data display has been used to determine whether the process is stable and what is the current sigma level of the process
  • The ability of the current process to meet customer needs has been established

Six Sigma tools frequently used in Measure step

  • Data collection plan
  • Gage R&R
  • Prioritization matrix
  • Run chart
  • Control chart
  • Histogram
  • Pareto charts
  • Process sigma calculation

What is Gage R&R?

  • Gage R&R = Gage Repeatability and Reproducibility study.
  • It evaluates the effectiveness of a measurement system.
  • Many of the measurement issues are due to poor operational definitions of a defect.
  • An operational definition identifies what is a good or defective output as well as the measurement process and specific tools (gages) which should be used for measurement.

Step 3: Analyze the process

  • In this step the team gets into the details, and enhances its understanding of the process and the problem.
  • It tries to identify the culprit behind the problem.
  • The team focuses on determining the “root cause”.
  • Sometimes the root cause is easy to determine, which helps the team to move through the analysis step quickly.
  • Sometimes it may take weeks and months to determine the root cause after using various tools and testing methods.
  • It is important to consider many types of causes, so as not to let biases or past experience cloud the judgment.

Example of common “root causes”

  • Methods: The procedures or techniques used in doing the work.
  • Machines: The technology, such as computers, copiers, or manufacturing equipment, used in the workplace.
  • Material: The data, instructions, machined parts, facts or numbers, forms and files that are flawed, will have negative impact on the output.
  • Measures: Faulty method of measuring a process on the basis of what’s measured and how.
  • Environment: Environmental factors such as heat, cold etc. can influence the output.
  • People: It is the key variable in how all these other elements combine to effect the output.

Sigma capability conversion table

Steps to calculate sigma value

  • Let us examine a Pizza delivery process
  • Let us assume there are four main customer requirements: correct ingredients, delivered hot, on time, & undamaged.
  • Data was collected on 500 delivered pizza. Following is the data form customer feedback: 25 were late, 10 were too cold, 7 were damaged, and 16 had wrong ingredients.
  • Total number of defects = 25+10+7+16 = 58
  • Number of defect opportunities = 500 x 4 = 2000
  • Defects per opportunity (DPO) = 58/2000 = 0.029
  • Defects per million opportunities (DPMO) = 0.029x106
  • DPMO = 29,000, check the table for current sigma value

Answer: The current pizza process is at 3.3 sigma

Action plan for the Analyze step

  • The action begins by combining experience, data/measure, and the review of the process and then forming an initial guess, or the hypothesis of the cause.
  • The team then looks for more data and other evidence to see whether it fits with the suspected cause.
  • The cycle of analysis continues, with the hypothesis being refined or rejected until the true root cause is identified or verified with data.
  • One of the big challenges in this Analyze step is to use the right tool. When causes go deeper or when the relationship between the problem and other factor is complex and hidden, more advanced statistical techniques may be required.

What should be accomplished in Analyze step?

  • Potential causes have been identified
  • Detailed process map has been created
  • Value-added flow analysis has been used to identify opportunities for process improvement
  • Potential causes have been verified and quantified with respect to their impact on process performance, using statistical techniques

Six Sigma tools frequently used in Analyze step

  • Process map
  • Value-added flow diagram
  • Cause-and-effect diagram (fishbone diagram)
  • Regression analysis and scatter plots
  • Hypothesis testing
  • Design of Experiments (DOE)

Step 4: Improve the process

  • Once the team has realigned its goals, Improve is the next step for finally planning and achieving results.
  • One of the major challenge of this step is that new ideas which are developed, have to be tested, refined, and implemented.
  • When several potential solutions have been proposed, several criteria, including costs and likely benefits, are used to select the most promising and practical solutions.
  • The “final” solution or series of changes must always be approved by the project champion and the entire leadership team.

Implementation is the key to the Improve step

  • Implementations have to be carefully managed and tested.
  • Small-scale pilots are practically mandatory.
  • Determine what could go wrong and prepare to prevent or manage difficulties.
  • New changes have to be “sold” to organization members whose participation is critical.
  • Data must be gathered to track and verify the impact (and unintended consequences) of the solution.

What should be accomplished in Improve step?

  • An effective solution that addresses the root cause of the problem
  • An analysis that documents the potential impact of the solution as well as the cost of implementing it (cost-benefit analysis)
  • A pilot phase to test that the solution works
  • An evaluation of the implementation risk resulting in preventive actions if necessary (FMEA)
  • A comprehensive plan to implement the solution, including budgets, timeliness, and responsibilities.

Six Sigma tools frequently used in Improve step

  • Idea generation techniques (brainstorming)
  • Prioritization matrix
  • Cost-benefit analysis
  • Piloting
  • Failure Mode and Effect Analysis (FMEA)
  • Project management tools
  • Stakeholder planning

What is FMEA?

  • FMEA = Failure Mode and Effect Analysis
  • Once the solution is approved, the team proceeds with an evaluation of potential implementation risks, using FMEA.
  • It is a structured approach to identify, estimate, prioritize, and evaluate the risk involved in the proposed solution.
  • In many cases, the team may has to revise the original solution to prevent potential problems.

Step 5: Control the process

  • Develop a monitoring process to keep track of the changes, which have been implemented.
  • Create a response procedure for dealing with problems that may arise.
  • Focus management’s attention on few critical measures that gives them the outcome of the project (Y) and the key input measures (Xs).
  • “Sell” the project through presentations and demonstrations.
  • Give the project responsibilities to those who will continue to work on the new process.
  • Ensure support from the management for the long term goals of the project.

What should be accomplished in Control step?

  • The results have been evaluated, documented, and approved.
  • The plans are in place to ensure that the gains continue to be maintained.
  • The training of appropriate people is complete.
  • Standardization strategy is in place that ensures that the variation of the new process is minimal.
  • The project is properly documented and has been handed over to the process owner (project closure).

Six Sigma tools frequently used in Control step

  • Process sigma calculation
  • Control charts
  • Standardization
  • QC charts and response plans

Simple interpretation of DMAIC steps

Define phase determines what is important to the customer.

Measure phase focuses on the understanding of the process.

Analysis phase determines the major cause of defects.

Improve phase removes the major causes of defects.

Control phase maintains the improvement.

The key to the success of DMAIC process

  • DMAIC process has been referred as an iterative process.
  • The line from “Define” to “Control” is not straight but rather back-and-forth.
  • It requires revisiting earlier assumptions and filling places passed over in haste.
  • The key to the success of the DMAIC process is to be flexible in dealing with continuous change and the ability to absorb and to interpret information.
  • It is important to remain open and attentive to the input of many stakeholders within and outside the project team.