The Control Phase represents the final and perhaps most critical stage of the DMAIC (Define, Measure, Analyze, Improve, Control) methodology in Lean Six Sigma. After investing significant time and resources into improving a process, organizations must ensure that these gains are maintained over time. This comprehensive guide explores the essential Control Phase tools that help organizations sustain improvements and prevent regression to previous performance levels.
Understanding the Control Phase
The Control Phase serves as the foundation for long-term success in any process improvement initiative. Without proper control mechanisms, even the most well-executed improvements can deteriorate, returning processes to their original state of inefficiency. The primary objective of this phase is to institutionalize improvements, monitor process performance, and quickly identify any deviations that require corrective action. You might also enjoy reading about How to Calculate and Implement Standard Time in Your Organization: A Complete Guide.
Control Phase tools provide the structure and methodology needed to maintain process stability, ensure consistent quality, and create a culture of continuous improvement. Let us examine the most effective tools and how to implement them in your organization. You might also enjoy reading about How to Implement Detection Controls: A Complete Guide to Quality Management.
Statistical Process Control Charts
Statistical Process Control (SPC) charts represent one of the most powerful tools for monitoring process performance over time. These charts help teams distinguish between common cause variation (inherent to the process) and special cause variation (resulting from specific, identifiable factors).
How to Create and Use Control Charts
Consider a manufacturing example where a company produces metal components with a target thickness of 5.0 millimeters. After implementing improvements, the team needs to monitor whether the process remains stable.
To create a control chart, follow these steps:
- Collect at least 20-25 subgroups of data from your improved process
- Calculate the mean (average) and standard deviation for each subgroup
- Determine the overall process mean and control limits
- Plot the data points on the chart with the centerline and upper and lower control limits
- Monitor future measurements and investigate any points that fall outside the control limits
For our manufacturing example, suppose we collected measurements over 25 days with five samples per day. The overall mean thickness is 5.02 mm, with an upper control limit of 5.08 mm and a lower control limit of 4.96 mm. Any measurement falling outside these limits would signal a need for investigation and corrective action.
Control Plans
A Control Plan serves as a living document that outlines how a process will be monitored and controlled. This comprehensive tool details what needs to be measured, how frequently measurements should occur, who is responsible for monitoring, and what actions should be taken when issues arise.
Developing an Effective Control Plan
An effective Control Plan includes several critical elements. The process description identifies which process or subprocess is being controlled. Key process inputs and outputs specify the variables that significantly impact quality. Measurement specifications detail how measurements will be taken, including the measurement system and frequency. Reaction plans describe the specific actions to take when the process shows signs of instability.
For instance, in a customer service call center that improved average call handling time from 8 minutes to 5 minutes, the Control Plan might specify monitoring average handling time daily, with a target of 5 minutes plus or minus 30 seconds. If the average exceeds 5.5 minutes for two consecutive days, the plan would trigger a review of call recordings and agent feedback to identify the cause.
Process Documentation and Standard Operating Procedures
Standard Operating Procedures (SOPs) ensure that improvements are consistently applied by documenting the new, improved process in detail. Without clear documentation, process variations can occur as different employees interpret procedures differently or new employees lack proper guidance.
Creating Robust Standard Operating Procedures
Effective SOPs should be clear, concise, and actionable. Begin by documenting each step of the improved process in sequential order. Include the purpose of each step, the responsible party, required materials or tools, specific instructions, quality checkpoints, and safety considerations.
Consider a food processing facility that reduced contamination risks through improved sanitation procedures. The SOP would detail the exact cleaning agents to use, the concentration ratios (for example, 2 ounces of sanitizer per gallon of water), contact time requirements (minimum 2 minutes), verification methods (ATP swab testing with acceptable levels below 150 RLU), and the frequency of cleaning (after each production run and at shift changes).
Mistake Proofing (Poka-Yoke)
Poka-Yoke devices and methods prevent errors from occurring or make errors immediately obvious when they do occur. This tool is particularly valuable because it reduces reliance on vigilance and memory, which are inherently unreliable human qualities.
Implementing Mistake Proofing Solutions
There are two primary types of mistake proofing: prevention (making it impossible to perform an action incorrectly) and detection (identifying when an error has occurred before it causes problems).
In a pharmaceutical packaging operation, the company might implement a weight verification system that checks each bottle before sealing. If the target is 100 tablets at 500 mg each (total weight 50 grams plus 10 grams for the bottle), the system would reject any bottle weighing less than 59 grams or more than 61 grams, preventing underfilled or overfilled bottles from reaching customers.
Response Plans and Escalation Procedures
Even with robust controls in place, processes will occasionally experience problems. Response plans provide clear guidance on how to address issues quickly and effectively, minimizing their impact.
Developing Comprehensive Response Plans
A well-structured response plan includes trigger conditions that specify exactly when the plan should be activated, immediate containment actions to prevent defects from reaching customers, root cause investigation protocols, corrective actions to address the immediate problem, and preventive actions to eliminate the underlying cause.
For example, an e-commerce fulfillment center that improved order accuracy from 94% to 99.5% might establish the following response plan: if order accuracy falls below 99% for any single day, immediately audit the next 50 orders manually. If accuracy falls below 98% or remains below 99% for three consecutive days, halt operations in the affected zone, retrain all staff, and review the picking process for system errors.
Ongoing Training and Capability Building
Sustaining improvements requires that all team members understand the improved process and their role in maintaining it. Regular training ensures that knowledge is transferred effectively and that new employees are properly onboarded.
Establishing a Training Framework
Create a structured training program that includes initial training for all current employees on the improved process, regular refresher training (quarterly or semi-annually), new hire orientation that emphasizes the importance of following established procedures, cross-training to build flexibility and understanding, and periodic assessments to verify competency.
A manufacturing team might implement a certification program where operators must demonstrate proficiency in the new process by completing a practical assessment with 100% accuracy on critical steps and at least 95% accuracy on standard steps. Recertification would occur annually to ensure skills remain sharp.
Performance Monitoring and Dashboards
Visual management tools like dashboards provide real-time visibility into process performance, enabling quick identification of trends and issues. Effective dashboards display key metrics in an easily digestible format that allows stakeholders at all levels to understand process health at a glance.
Creating Effective Performance Dashboards
Select three to five key performance indicators that directly reflect the improvements made. Display current performance against target, trend information showing performance over time, and status indicators (such as green for on-target, yellow for caution, and red for immediate attention required).
A logistics company that reduced delivery delays might track on-time delivery percentage (target: 98%), average delay time when delays occur (target: less than 30 minutes), customer complaints related to delivery (target: fewer than 5 per month), and cost per delivery (target: $12.50 or less). This dashboard would be reviewed daily by operations managers and weekly by senior leadership.
Maintaining the Gains Through Culture
Tools and procedures provide the mechanics of control, but organizational culture determines whether these mechanisms will be sustained long-term. Creating a culture of continuous improvement requires leadership commitment, employee engagement, recognition of adherence to standards, and regular communication about the importance of maintaining improvements.
Organizations that successfully sustain improvements celebrate wins, share success stories, provide regular feedback on performance, involve frontline employees in problem-solving, and allocate resources for ongoing improvement activities. When employees understand why controls matter and feel ownership of the process, compliance becomes natural rather than forced.
Conclusion
The Control Phase tools discussed in this guide provide the framework necessary to sustain process improvements and prevent backsliding. Statistical Process Control charts offer quantitative monitoring, Control Plans provide comprehensive oversight, Standard Operating Procedures ensure consistency, mistake proofing prevents errors, response plans enable quick action, training builds capability, and dashboards maintain visibility.
Successfully implementing these tools requires commitment, discipline, and ongoing attention. However, the investment pays significant dividends by protecting the improvements you have worked hard to achieve and creating a foundation for future enhancements.
The most successful organizations view the Control Phase not as the end of an improvement project but as the beginning of sustained excellence. By mastering these tools and integrating them into daily operations, you can ensure that your process improvements deliver lasting value.
Enrol in Lean Six Sigma Training Today and gain the comprehensive skills needed to lead successful improvement initiatives from start to finish. Our certification programs provide hands-on experience with Control Phase tools and all aspects of the DMAIC methodology. Whether you are seeking Yellow Belt, Green Belt, or Black Belt certification, our expert instructors will guide you through practical applications and real-world case studies. Do not let your process improvements fade over time. Invest in professional training that equips you with the knowledge and tools to sustain excellence. Contact us today to explore our training options and take the next step in your continuous improvement journey.
