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Chapter 17 – Control Phase (DMAIC) - Coggle Diagram
Chapter 17 – Control Phase (DMAIC)
Purpose of the Control Phase
Sustain improvements achieved in the Improve phase
Prevent the process from returning to old behaviors
Ensure gains are measurable, repeatable, and stable
Transfer ownership from project team to process owners
Transition From Improve to Control
Solutions have already been tested and validated
Process changes are formally implemented
Focus shifts from improvement to long-term stability
Risks are reviewed before full handoff
Control Plan
Primary document used to maintain improvements
Defines how the process will be monitored and controlled
Serves as a reference for daily operations
Key Elements of a Control Plan
Critical process steps and outputs
Key performance metrics to be monitored
Measurement methods and data frequency
Responsible owners for each control activity
Reaction plans when performance drifts
Standard Operating Procedures (SOPs)
Document the new and improved way of working
Replace informal or outdated practices
Ensure consistency across people and shifts
Support training and onboarding
Visual Controls
Examples of Visual Controls
Dashboards showing key metrics
Color coding for status or priorities
Checklists and posted work instructions
Andon signals or alerts
Make process performance visible and obvious
Reduce reliance on memory or judgment
Help teams identify issues quickly
Control Charts
Key Control Chart Concepts
Center line represents process average
Control limits define expected variation
Points outside limits signal special causes
Patterns or trends indicate instability
Primary tool for monitoring process stability
Distinguish between common and special cause variation
Prevent overreaction to normal variation
Response and Reaction Plans
Define actions when control limits are violated
Prevent confusion during process issues
Ensure fast and consistent responses
Reaction Plan Includes
What immediate action is required
How the issue is investigated
When normal operation can resume
Who must be notified
Mistake Proofing (Poka-Yoke)
Prevent errors before they occur
Reduce dependence on inspection
Improve reliability of the process
Documentation and Lessons Learned
Capture what worked and what did not
Document key decisions and trade-offs
Support future improvement projects
Increase organizational learning
Project Closure and Handoff
Formal handoff to process owner
Confirmation that controls are in place
Sponsor approval of project completion
Team recognition and closure
Mistake Proofing Approaches
Physical constraints that block incorrect actions
Automated checks or system alerts
Sequencing steps to avoid omissions
Simplifying tasks to reduce human error
Training and Knowledge Transfer
Ensure process owners understand new controls
Reinforce correct behaviors and expectations
Support long-term sustainability
Control Phase Tollgate Checklist
Control plan is complete and approved
SOPs are updated and in use
Control charts are active and monitored
Reaction plans are defined and understood
Process owner accepts responsibility
Improvements are stable and sustainable