Introduction to the Control Phase in Six Sigma

Control Phase

Once a Six Sigma project has reached the Control phase, it means that all the hard work and analysis have paid off. This is the final step in the Six Sigma methodology. Primarily, the focus shifts towards maintaining the improvements made. Also, it ensures that the processes continue to perform at the desired level. This phase is crucial for the long-term success of any Six Sigma project.

During the Define, Measure, Analyze, and Improve phases, the Six Sigma team identifies the root causes of the defects, implements process changes, and achieves a significant reduction in defect rates. The main goal of the Control phase is to establish a system that monitors and sustains the improvements achieved in the Improve phase. Here’s an explanation of the Control phase and the activities you should consider:

Control Phase Activities:

  1. Establishing Control Plan:

    Create a detailed control plan that outlines the strategies and methods for monitoring the process on an ongoing basis. The control plan should outline who will collect the data, how they will collect it, and the frequency of data collection.

  2. Implementing Control Measures:

    Put the control plan into action and start collecting data based on the defined control measures. Design these measures to monitor the key process variables and ensure they stay within acceptable limits.

  3. Process Monitoring:

    Continuously monitor the process using control measures. For this purpose, you can use Statistical process control (SPC) charts, dashboards, or other data visualization tools. The goal is to detect any variations or deviations from the desired performance.

  4. Corrective Actions:

    If you identify any deviations or non-conformities during process monitoring, it’s essential to have predefined corrective actions in place. Trigger these actions when certain thresholds and limits are exceeded.

  5. Standard Operating Procedures (SOPs):

    Update or create standard operating procedures to reflect the improved process. Ensure that the team follows these new procedures consistently.

  6. Training and Knowledge Transfer:

    Provide training to the process operators and stakeholders to ensure they understand the changes and improvements made during the project. Knowledge transfer is critical for sustaining the gains achieved.

  7.  Documenting Results:

    Keep track of the results and improvements achieved throughout the project. During the Control phase, document the final state of the process after improvements, along with the performance indicators that you will be monitoring.

Deliverables in the Control Phase of DMAIC:

  1. Control Plan:

    A comprehensive plan that outlines monitoring and control of the process going forward. This includes data collection methods, frequency, and the responsible individuals.

  2. Control Measures and Monitoring System:

    Clearly defined metrics and tools to monitor the process on an ongoing basis, such as SPC charts or dashboards.

  3. Corrective Action Plan:

    A set of predefined actions if the process deviates from the desired performance.

  4. Updated Standard Operating Procedures (SOPs):

    Revised procedures reflecting the improvements made during the project, ensuring consistency in the process.

  5. Training Documentation:

    Materials and records of training sessions conducted to educate process operators and stakeholders about the changes and improvements.

  6. Results Documentation:

    A comprehensive report detailing the final state of the process after improvements and the performance indicators that the team will monitor during the Control phase.

A crucial element in this phase is the implementation of statistical process control (SPC) techniques. SPC involves monitoring the process performance using statistical tools and methods. By collecting and analyzing data, the team can identify any deviations from the desired performance and take corrective actions promptly. For instance, the manufacturing company in our example might measure defect rates regularly, track the data on control charts, and set control limits to flag any significant changes.


In conclusion, the Control phase in Six Sigma is a critical stage where the focus shifts from making improvements to sustaining them. It involves implementing controls, setting up monitoring mechanisms, and creating a plan for ongoing process management. By establishing standard operating procedures, implementing statistical process control techniques, and developing a robust monitoring and auditing system, organizations can ensure that the improvements made during the Six Sigma project become a permanent part of their operations.

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