Lean Manufacturing and Six Sigma practitioners use slightly different terminology and methodologies for process improvement, but they are really more similar than different. Let’s compare the different terminology and methods.
The term kaizen is used in two ways: (1) kaizen is used to represent the general continuous improvement process which would be similar to the general DMAIC process in Six Sigma practices, and (2) in relation to kaizen workshops which are intense rapid problem solving activities to tackle problems identified as high priority.
Six Sigma practitioners use the DMAIC process to systematically reduce variability in a manufacturing process. Lean practitioners refer to the Toyota problem solving methodology and to kaizen events. For diving down into specific urgent issues once they are uncovered, the Toyota Problem Solving process and the 8-Discipline (8D) process are very similar. The 8D process seems more appropriate to quality issues because it directly adds a step to contain the problem. Both are explained below.
DMAIC
Analyze – This phase involves identifying the root causes of the defects using appropriate statistical tools.
Improve – In this phase solutions to address the problems identified are applied. Lean methods such as 5S, Standardized work content, cellular manufacturing layouts, mistake-proofing, Total Productive Maintenance are applied.
Control – This phase involves institutionalizing the improvement methods. Policies, procedures and other management systems are modified to achieve the goals.
Performance results are periodically monitored to ensure that the improvements are sustained.
However, TPS practitioners have adopted an extended problem-solving methodology that puts more emphasis on identifying the root cause.
Toyota Problem-Solving Process
Initial Problem Perception – The initial problem reported by employees is documented. Problem may seem vague and complicated at the beginning.
Clarify Problem – Getting a better grasp of the situation requires an observation of the problem at the site with an open mind. Pareto diagrams use bar graphs to sort problems according to their severity, frequency, nature and source and point out the most important problems in the area.
Initial Point of Cause (POC) – Identify targets for improvements and a likely cause to use as a starting point for further cause exploration.
Investigate Root cause – Answer the “Why?” question five times to narrow down to the real root cause.
Countermeasure – Define a countermeasure to eliminate the root cause identified.
Evaluate – It is critical to allow time or a few units to pass through the new process before we evaluate the effectiveness of the corrective action.
Standardize – Only after verification of the effectiveness of the corrective action, should we proceed to standardize the solution by modifying work instructions and standard manufacturing procedures.
Kaizen Workshops
When analyzing the macro value stream of a company, continuous improvement efforts can seem too big to tackle. It is often easier to divide the macro value stream into several smaller subprocesses. If critical problems are identified in smaller subprocesses they can be tackled with kaizen workshops.
A kaizen workshop is an intensive rapid improvement model that emphasizes creativity and radical improvement. The methodologies of value stream mapping and the Toyota problem-solving process are implemented in a compressed time frame. The workshops are typically full time for 3 to 5 days and participants analyze the current process, develop a new lean process and perhaps even begin implementation.
The team size should be limited to no more than 15. The kaizen workshop is headed by the manager responsible for the process (“process owner”) and should include people form the work area, and customers and suppliers to the process.
Preparing for a kaizen workshop involves the following:
• Identify process scope, customer, suppliers, and symptoms to tackle
• Create value stream map for current process
• Collect relevant metrics, facts and documents describing the current process
• Post the current state map in the workshop room
The kaizen workshop includes the following steps:
• Analyze and assess non-value added activities in current practices
• Brainstorm different improvements
• Develop recommendations for new process
• Create value stream map for new process
• Use a “parking-lot” list for potential process improvements with lower priorities
• Obtain management approval on recommendations
• Plan and initiate process improvements
After the kaizen workshop it is important to:
• Follow up to make sure the new process is implemented
• Measure the effect of the new process on process metrics
• Develop visual controls and standardize the new process
• Prepare presentation to management on process improvements and recognize the team achievements
• Review items left in the “parking-lot” for future improvements
• Select the next area to tackle for process improvement
8D Problem Solving Process
When responding to quality issues in the plant or supply chain, the 8-Disciplines (8D) process is often used because it adds steps to immediately contain the problem. The Toyota Problem-Solving process and the 8D process have a lot of similarities but in many ways do not exactly align. The 8D process has an emphasis on corrective and preventive actions which are more appropriate to obvious quality issues, and the Toyota Problem-Solving process has more emphasis on defining the problem which might not be obvious on productivity issues.
Form the Team – The 8D process recognizes the importance of assembling the right team and places it as the first step. A small team is needed with the right mix of skills, experience and authority to resolve the problem and implement solutions. Ensure that everyone on the team has the time and inclination to work on the problem together.
Formal meetings should initiate the effort and monitor progress. The company’s Corrective Action Database should be used to document findings, decisions and progress.
Describe the Problem – It is critical to define a clear problem. The problem statement provides the starting point for investigation. Terms used in the description must be understood by the entire team. Problem description should include the following:
(a) Who – Who is affected by the problem? Who first observed the problem? To whom was the problem reported to?
(b) What – What type of problem? What has the problem? What is or isn’t happening? What is the physical evidence?
(c) When – When did it first happen? When was it first observed? Is it a recurring problem? How often? What is the trend? (random, cyclical, continuous) Has it been observed before?
(d) How Much – What is the magnitude of the problem? How many units or components are affected? How much cost (labor and material) is associated to this problem?
(e) Why – Why is it a problem? What is the impact? What processes are affected? Is production stopped completely or partially? Is there a work-around? Are customer delivery dates impacted?
Contain the Problem – Identify interim containment actions to prevent further cost impact from the problem. Is the problem tied to a machine? Is it tied to a supplier component? Are more lots affected by this problem? Suppliers must be informed as soon as possible about issues to prevent further shipments with problems. Inventory parts which might be affected must be identified and inspected. If problem
has a life-threatening consequence, products in the field have to be identified for potential recall.
Identify the Root cause – An investigation and failure analysis is performed to determine the root cause of the problem. It is not enough to identify the first-level or intermediate-level causes of the problem. The true root cause has to be uncovered and corrected or a similar problem will eventually manifest itself.
Root cause analysis may start with brainstorming sessions among team members and move on to data analysis that further explores multiple potential causes. Different kinds of charts and diagrams are used in data analysis including histograms, Pareto charts, scatter charts, and concentration and affinity diagrams.
It is important to document the analysis discussion, findings and conclusions using cause-and-effect charts and fault tree diagrams. A five-whys type of analysis is also useful to understand all the intermediate-level causes between the root cause and the problem manifestation.
Corrective Actions – This discipline entails identifying all possible corrective actions to address the root cause of the problem. The owners of the corrective actions, the target dates for completion and the rationale behind each should be documented. It is sometimes a good idea to have a preliminary evaluation of the corrective action to test its effectiveness before wasting time and money on fully
implementing an incorrect solution.
Corrective action includes further containment of potentially affected similar production or inventory based on the root cause identified. If problem has a life-threatening consequence, products in the field have to be identified and notifications issued for recall or repair.
Permanent Correction – Once the corrective actions have been defined and tested, the next step it to implement them and verify their effectiveness. If the corrective actions are found to have deficient effectiveness it might be necessary to return to the prior step and create new corrective actions.
Preventive Actions – Lessons learned from the above investigation and corrective actions might be able to benefit other processes or areas with similar vulnerabilities even if not affected under the current
situation. Preventive measures should be outlined if its possible to prevent similar problems in the future. Preventive actions, like corrective actions, require owners and target dates.
Acknowledge Success – The last step of the 8D process is management’s formal recognition of the accomplishments of the team. This demonstrates the commitment of the management team to the continuous improvement process and is good internal publicity for the effectiveness of these initiatives.
The Continuous Improvement Tracking System
Common to any methodology is the need to document findings, actions and results. A key component of the enterprise manufacturing and quality system is the database that will document and track on-going process improvement efforts ensuring a consistent review process and verification of
effectiveness of any corrective action. The same database log can be used to track and resolve productivity or quality problems. The effectiveness of process improvements should
be reflected and documented in relation to improvements in key operational metrics.
The term kaizen is used in two ways: (1) kaizen is used to represent the general continuous improvement process which would be similar to the general DMAIC process in Six Sigma practices, and (2) in relation to kaizen workshops which are intense rapid problem solving activities to tackle problems identified as high priority.
Six Sigma practitioners use the DMAIC process to systematically reduce variability in a manufacturing process. Lean practitioners refer to the Toyota problem solving methodology and to kaizen events. For diving down into specific urgent issues once they are uncovered, the Toyota Problem Solving process and the 8-Discipline (8D) process are very similar. The 8D process seems more appropriate to quality issues because it directly adds a step to contain the problem. Both are explained below.
DMAIC
Six Sigma practitioners use the DMAIC process to systematically reduce variability in a manufacturing process.
Define – This phase focuses on defining the project goalsand activities and identifying the issues that need to be addressed.
Measure – In this phase information about the target process is gathered. Metrics are used to determine current performance and to identify problems and issues.Analyze – This phase involves identifying the root causes of the defects using appropriate statistical tools.
Improve – In this phase solutions to address the problems identified are applied. Lean methods such as 5S, Standardized work content, cellular manufacturing layouts, mistake-proofing, Total Productive Maintenance are applied.
Control – This phase involves institutionalizing the improvement methods. Policies, procedures and other management systems are modified to achieve the goals.
Performance results are periodically monitored to ensure that the improvements are sustained.
However, TPS practitioners have adopted an extended problem-solving methodology that puts more emphasis on identifying the root cause.
Toyota Problem-Solving Process
Initial Problem Perception – The initial problem reported by employees is documented. Problem may seem vague and complicated at the beginning.
Clarify Problem – Getting a better grasp of the situation requires an observation of the problem at the site with an open mind. Pareto diagrams use bar graphs to sort problems according to their severity, frequency, nature and source and point out the most important problems in the area.
Initial Point of Cause (POC) – Identify targets for improvements and a likely cause to use as a starting point for further cause exploration.
Investigate Root cause – Answer the “Why?” question five times to narrow down to the real root cause.
Countermeasure – Define a countermeasure to eliminate the root cause identified.
Evaluate – It is critical to allow time or a few units to pass through the new process before we evaluate the effectiveness of the corrective action.
Standardize – Only after verification of the effectiveness of the corrective action, should we proceed to standardize the solution by modifying work instructions and standard manufacturing procedures.
Kaizen Workshops
When analyzing the macro value stream of a company, continuous improvement efforts can seem too big to tackle. It is often easier to divide the macro value stream into several smaller subprocesses. If critical problems are identified in smaller subprocesses they can be tackled with kaizen workshops.
A kaizen workshop is an intensive rapid improvement model that emphasizes creativity and radical improvement. The methodologies of value stream mapping and the Toyota problem-solving process are implemented in a compressed time frame. The workshops are typically full time for 3 to 5 days and participants analyze the current process, develop a new lean process and perhaps even begin implementation.
The team size should be limited to no more than 15. The kaizen workshop is headed by the manager responsible for the process (“process owner”) and should include people form the work area, and customers and suppliers to the process.
Preparing for a kaizen workshop involves the following:
• Identify process scope, customer, suppliers, and symptoms to tackle
• Create value stream map for current process
• Collect relevant metrics, facts and documents describing the current process
• Post the current state map in the workshop room
The kaizen workshop includes the following steps:
• Analyze and assess non-value added activities in current practices
• Brainstorm different improvements
• Develop recommendations for new process
• Create value stream map for new process
• Use a “parking-lot” list for potential process improvements with lower priorities
• Obtain management approval on recommendations
• Plan and initiate process improvements
After the kaizen workshop it is important to:
• Follow up to make sure the new process is implemented
• Measure the effect of the new process on process metrics
• Develop visual controls and standardize the new process
• Prepare presentation to management on process improvements and recognize the team achievements
• Review items left in the “parking-lot” for future improvements
• Select the next area to tackle for process improvement
8D Problem Solving Process
When responding to quality issues in the plant or supply chain, the 8-Disciplines (8D) process is often used because it adds steps to immediately contain the problem. The Toyota Problem-Solving process and the 8D process have a lot of similarities but in many ways do not exactly align. The 8D process has an emphasis on corrective and preventive actions which are more appropriate to obvious quality issues, and the Toyota Problem-Solving process has more emphasis on defining the problem which might not be obvious on productivity issues.
Form the Team – The 8D process recognizes the importance of assembling the right team and places it as the first step. A small team is needed with the right mix of skills, experience and authority to resolve the problem and implement solutions. Ensure that everyone on the team has the time and inclination to work on the problem together.
Formal meetings should initiate the effort and monitor progress. The company’s Corrective Action Database should be used to document findings, decisions and progress.
Describe the Problem – It is critical to define a clear problem. The problem statement provides the starting point for investigation. Terms used in the description must be understood by the entire team. Problem description should include the following:
(a) Who – Who is affected by the problem? Who first observed the problem? To whom was the problem reported to?
(b) What – What type of problem? What has the problem? What is or isn’t happening? What is the physical evidence?
(c) When – When did it first happen? When was it first observed? Is it a recurring problem? How often? What is the trend? (random, cyclical, continuous) Has it been observed before?
(d) How Much – What is the magnitude of the problem? How many units or components are affected? How much cost (labor and material) is associated to this problem?
(e) Why – Why is it a problem? What is the impact? What processes are affected? Is production stopped completely or partially? Is there a work-around? Are customer delivery dates impacted?
Contain the Problem – Identify interim containment actions to prevent further cost impact from the problem. Is the problem tied to a machine? Is it tied to a supplier component? Are more lots affected by this problem? Suppliers must be informed as soon as possible about issues to prevent further shipments with problems. Inventory parts which might be affected must be identified and inspected. If problem
has a life-threatening consequence, products in the field have to be identified for potential recall.
Identify the Root cause – An investigation and failure analysis is performed to determine the root cause of the problem. It is not enough to identify the first-level or intermediate-level causes of the problem. The true root cause has to be uncovered and corrected or a similar problem will eventually manifest itself.
Root cause analysis may start with brainstorming sessions among team members and move on to data analysis that further explores multiple potential causes. Different kinds of charts and diagrams are used in data analysis including histograms, Pareto charts, scatter charts, and concentration and affinity diagrams.
It is important to document the analysis discussion, findings and conclusions using cause-and-effect charts and fault tree diagrams. A five-whys type of analysis is also useful to understand all the intermediate-level causes between the root cause and the problem manifestation.
Corrective Actions – This discipline entails identifying all possible corrective actions to address the root cause of the problem. The owners of the corrective actions, the target dates for completion and the rationale behind each should be documented. It is sometimes a good idea to have a preliminary evaluation of the corrective action to test its effectiveness before wasting time and money on fully
implementing an incorrect solution.
Corrective action includes further containment of potentially affected similar production or inventory based on the root cause identified. If problem has a life-threatening consequence, products in the field have to be identified and notifications issued for recall or repair.
Permanent Correction – Once the corrective actions have been defined and tested, the next step it to implement them and verify their effectiveness. If the corrective actions are found to have deficient effectiveness it might be necessary to return to the prior step and create new corrective actions.
Preventive Actions – Lessons learned from the above investigation and corrective actions might be able to benefit other processes or areas with similar vulnerabilities even if not affected under the current
situation. Preventive measures should be outlined if its possible to prevent similar problems in the future. Preventive actions, like corrective actions, require owners and target dates.
Acknowledge Success – The last step of the 8D process is management’s formal recognition of the accomplishments of the team. This demonstrates the commitment of the management team to the continuous improvement process and is good internal publicity for the effectiveness of these initiatives.
The Continuous Improvement Tracking System
Common to any methodology is the need to document findings, actions and results. A key component of the enterprise manufacturing and quality system is the database that will document and track on-going process improvement efforts ensuring a consistent review process and verification of
effectiveness of any corrective action. The same database log can be used to track and resolve productivity or quality problems. The effectiveness of process improvements should
be reflected and documented in relation to improvements in key operational metrics.
References
“The Toyota Way”, Jeffrey K. Liker, McGraw Hill, 2004
“Lean Six Sigma”, Michael L. George, McGraw Hill, 2002
“Root Cause Analysis”, Bjorn Andersen and Tom Fagerhaug, ASQ Quality Press, 2006