Six Sigma Control Plan

The Fifth Step – Control

A six sigma project is not complete, until you create and execute a control plan.

During this fifth step, you need to:

1. Identify the critical process or product characteristics you need to track
2. Determine the specific metrics which will flag the process or product as out of control
3. Design the methods you will use to collect relevant measurements
4. Develop a reaction plan articulating what will happen if the process or product gets out of control
5. Transition ownership of the control plan from the six sigma project team to the owner of the process

A control plan is designed to ensure the changes implemented during the improve step become the new normal. If adjustments are needed, as changes are rarely perfect, then a structure is in place to react as appropriate.

While much is expected from a control plan, it does not replace the need for documentation such as standard operating procedures, work instructions, quality specifications, and preventive maintenance requirements.

Enough about what a control plan is not. Let’s explore the five requirements listed above.

1. Identify Process or Product Characteristics

Most of the characteristics you need to track will come from things which changed as part of your implementation. Examples include:

• The process step which is new or has changed
• The product or part number which is new or has changed
• The product specification which has been changed or deemed important to track
• The improvement which has been made
• The targeted performance you expect from the process step or quality appraisal

As an example, you change the step for responding to customer emails and expect each customer to receive a response within 30 minutes. This information would be the first three columns in your control plan.

2. Determine Specific Metrics

Your next task is to determine the specific metrics you will track. These could include:

• Lower specification limit (LSL) – what will trigger the process or product as out of control
• Upper specification limit (USL) – what will trigger the process or product as out of control
• Specification width – USL minus LSL
• Lower control limit (LCL) – what is considered out of statistical control due to special cause variation
• Upper control limit (UCL) – what is considered out of statistical control due to special cause variation
• Process width – UCL minus LCL
• Capability index (Cpk)- see process capability analysis

Continuing our example, responding to customer emails may be deemed out of statistical control with an upper control limit of 1 hour. The lower control limit could be 15 minutes and be used to flag a very positive result. The team or process owner will want to find out why things are going better than expected.

A six sigma project which included “process capability analysis” will use LSL, USL, Cpk, and some of the additional metrics associated with the technique.

3. Methods to Collect Measurements

Time to identify how data will be collected. This may include:

• Measurement technique such as gauge, test device, mistake proofing fixture, software application, or manual reporting
• Inspection type such as judgment, informative, or source
• Frequency of sampling

Using our customer email example, the measurement technique might be a report from the email software which would be informative inspection. This would not involve random sampling. You could list 100% if the column is on the control plan and needs to be filled in.

4. Develop Reaction Plan

Great project teams hope for the best and prepare for excitement to arrive. The reaction plan needs to state what will happen if the process or product goes out of control. This could include:

• What will happen when the process or product is flagged as out of control
• Who is responsible for taking action

The spirit of the reaction plan must be to find the root cause and then eliminate the root cause for the out of control situation. If the out of control situation is better than expected performance, then it needs to be a learning opportunity and adjustments made to capture the better results as a new normal.

The reaction plan should not be a situation where you simply fix and forget the issue, seek approval from some executive to throw out the defects, or beat on people to work harder. A poorly designed reaction plan means the six sigma project can never exit the control phase and the project team will not be able to transfer ownership to the process owner.

In our customer email example, the reaction plan when average response time is over 1 hour could be to meet with the supervisor to determine the root cause and implement changes required to eliminate the root cause.

Such a simple statement as find and eliminate the root cause can be the reaction plan for many items on the control plan. Just don’t forget how hard it can be to find the root cause.

5. Transition Ownership

Six sigma projects are not meant to last forever. A competitive advantage of six sigma is how the methodology has 5 steps and delivers an improved process or improved quality which is in control.

A control plan will generally begin with the six sigma project team monitoring performance and end with a transfer of control to the process owner. It takes approval from both the project team and the process owner to announce the new process is in control and the project is coming to an end.

Acknowledging the need to transition ownership, on the control plan, could include:

• Project team for the relevant six sigma project
• Revision number of the control plan – this plan needs to adjust and will have revisions
• Revision date of the control plan
• Process owner – who owns the process step listed in the first column
• Transition date when ownership of the control plan will transfer from the project team to the process owner

For our customer email example, the transition to the customer service manager could occur after 2 or 3 weeks of monitoring the average daily response time. You should use the functional title, customer service manager of the process owner. People come and go.

Summary

A six sigma project is not complete, until you create and execute a control plan.

For a vast majority of six sigma projects, a control plan does not need to be long and complicated. Keep it simple. One source states the need for control plans of twenty pages or more. This alone would indicate the scope of the project was too large at the start.

For your control plans, use the columns which are needed. Don’t seek data which does not provide value.

For the type of project which is done during a green belt class, use the control plan template at: Template-Control-Plan

Mike Loughrin

Mike Loughrin is the CEO and Founder of Transformance Advisors. He also teaches for Louisiana State University Shreveport and is on the board of directors for the Association for Supply Chain Management Northern Colorado.

Mike brings exceptional experience in industry, consulting services, and education. Mike has helped organizations such as Levi Strauss, Warner Home Video, Lexmark, and Sweetheart Cup.

Keeping a commitment to a balanced life, Mike loves downhill skiing, bicycle rides, and hiking in the mountains. See one of his trails of the month at: Little Switzerland.

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