Control Phase in Lean Six Sigma: Sustaining Gains and Monitoring Process Performance
What Is the Control Phase?
The Control phase in Lean Six Sigma focuses on sustaining the improvements achieved during the Improve phase by establishing monitoring systems, standardizing processes, and ensuring that performance gains are maintained over time. It is where improved processes are stabilized and embedded into daily operations to prevent regression and ensure long-term success.
Why the Control Phase Matters
The Control phase is essential because improvements that are not actively managed can quickly erode.
Organizations that excel in this phase:
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Sustain performance gains over time
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Detect and respond to variation before it becomes a problem
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Ensure consistency through standardized processes
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Build accountability and ownership for ongoing performance
Without a structured Control phase, organizations risk reverting to previous performance levels, losing the benefits of their improvement efforts.
Key Concepts in the Control Phase
🔹Process Monitoring and Feedback
Continuously tracking key performance indicators (KPIs) to ensure the process remains stable and within expected limits, and providing timely feedback to appropriate front-line staff and management.
🔹Control Plans and Response Plans
Documented plans that outline how critical process variables will be monitored, controlled, and responded to if performance deviates, including actions to be taken when performance metrics indicate a deviation from expected outcomes.
🔹Standard Work
Establishing and documenting the best-known method for performing a process to ensure consistency and repeatability, and ensuring standard work is a part of training programs and onboarding new staff.
🔹Statistical Process Control (SPC)
Implementing and employing control charts and statistical methods to monitor process behavior and distinguish between normal variation and special causes.
🔹Process Ownership
Assigning clear responsibility for maintaining and improving process performance over time.
🔹Continuous Improvement
Recognizing that Control is not the end, but the beginning of ongoing monitoring and incremental improvement.
🔹Gemba Walks and Process Audits
Gemba ("go see") walks can contribute to process control through several key mechanisms including verifying standard work, early issue detection, real-time data collection, closing the gap between vision and reality, and sustaining improvements.
Common Tools Used in the Control Phase
🔹Statistical Process Control and Control Charts
Leverage statistical process control tools and methods to implement visual tools, including control charts, to monitor process performance over time and identify variation that may require action.
🔹Control Plans
Prepare structured, prescriptive documents that define how processes will be managed and sustained after improvements are implemented.
🔹Standard Operating Procedures (SOPs)
Provide detailed, prescriptive instructions that ensure processes are performed consistently and correctly.
🔹Process Dashboards
Design and implement real-time or periodic reporting tools that provide visibility into key performance metrics, including at the location where work is being performed and staff and operators require feedback.
🔹Visual Management
Construct and deploy visual cues such as charts, boards, and indicators to make process performance easily understood at a glance, especially by those closest to the work being performed.
🔹Audits and Layered Process Reviews
Establish protocols for regular checks to ensure that standard work is being followed and improvements are sustained.
🔹Poka-Yoke (Error Proofing)
Ensure mechanisms are in place that prevent errors or make them immediately detectable within the process so they do not travel downstream to the next process.
🔹Gemba Walks
Ensure that routines are established for gemba ("go see") walks performed by appropriate levels of management personnel.
🔹Daily Huddles
Ensure that daily huddles (or weekly equivalent) are in place to allow teams to rapidly share information that can inform the work being done, status of improvement initiatives, safety awareness, as well as identify opportunities for improvement.
Where Improve Fits in the DMAIC Framework
The Define phase sets the foundation for all subsequent phases:
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Define – Identify the problem and customer requirements
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Measure – Understand current performance using data
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Analyze – Identify root causes of issues and process improvement opportunities
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Improve – Design and Implement solutions
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Control – Lock in changes and sustain the improvement gains over time
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