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In the world of quality management and continuous improvement, achieving excellence is only half the battle. The real challenge lies in maintaining those hard-won gains over time. This is where the Control Phase of the DMAIC (Define, Measure, Analyze, Improve, Control) methodology becomes crucial, particularly in understanding and preventing process drift. Process drift, the gradual deviation of a process from its optimal performance standards, can silently erode the improvements you have worked so hard to implement.
What is Process Drift?
Process drift refers to the gradual and often unnoticed changes in a process that cause it to deviate from its established baseline or target performance. Unlike sudden process failures or dramatic shifts, process drift occurs incrementally, making it particularly insidious. Think of it as a ship slowly veering off course; without regular corrections, even a small deviation can lead you far from your intended destination. You might also enjoy reading about Control Phase: Creating Effective Escalation Procedures for Process Excellence.
Consider a manufacturing facility that produces precision components. Initially, the process produces parts with a target dimension of 50.0 millimeters with a tolerance of plus or minus 0.5 millimeters. Over several months, without proper monitoring and control, the average dimension might shift to 50.3 millimeters. While still within tolerance, this drift indicates that the process is moving away from its optimal center point, increasing the risk of future defects. You might also enjoy reading about Continuous Improvement Culture: Building Momentum After Six Sigma Success.
Understanding the Root Causes of Process Drift
To effectively prevent process drift, we must first understand what causes it. Several factors contribute to this phenomenon, and recognizing them is essential for implementing appropriate preventive measures.
Environmental Changes
External factors such as temperature, humidity, and seasonal variations can gradually affect process performance. A pharmaceutical company discovered that their tablet coating process performed differently during summer months compared to winter. The ambient temperature variations, though subtle, caused the coating material to behave differently, leading to inconsistent product quality.
Equipment Degradation
Machines and tools naturally wear over time. A printing company noticed that their color accuracy gradually declined over six months. Investigation revealed that the printing press rollers had worn down microscopically, causing subtle changes in ink application that accumulated into noticeable color shifts.
Human Factors
Changes in workforce composition, training gaps, or gradual modifications to work procedures can introduce drift. When experienced operators retire or new staff join without adequate training, subtle variations in process execution can emerge. Similarly, well-intentioned shortcuts or workarounds that develop over time can gradually move the process away from standard operating procedures.
Material Variation
Suppliers may make gradual changes to raw materials or components that affect your process. A bakery experienced process drift when their flour supplier slowly adjusted the protein content of their product over several batches, affecting dough consistency and baking times.
Real World Example: Customer Service Call Center
Let us examine a detailed example from a customer service call center to illustrate process drift and its prevention. The call center implemented improvements to reduce average call handling time from 8 minutes to 6 minutes while maintaining customer satisfaction scores above 4.5 out of 5.0.
Here is the baseline data after the improvement phase (Week 0):
- Average Call Handling Time: 6.0 minutes
- Customer Satisfaction Score: 4.7
- First Call Resolution Rate: 87%
- Calls per Agent per Day: 45
Without proper controls, the center experienced the following drift over 12 weeks:
Week 4:
- Average Call Handling Time: 6.3 minutes (5% increase)
- Customer Satisfaction Score: 4.6
- First Call Resolution Rate: 85%
Week 8:
- Average Call Handling Time: 6.8 minutes (13% increase)
- Customer Satisfaction Score: 4.4
- First Call Resolution Rate: 82%
Week 12:
- Average Call Handling Time: 7.4 minutes (23% increase)
- Customer Satisfaction Score: 4.2
- First Call Resolution Rate: 79%
Investigation revealed multiple causes: agents gradually became less adherent to the new scripts, the knowledge base was not being updated regularly, and coaching sessions had become inconsistent. The drift occurred so gradually that management did not notice the degradation until customer complaints increased.
Key Strategies for Preventing Process Drift
Statistical Process Control (SPC) Charts
Statistical Process Control charts are powerful tools for detecting process drift before it becomes problematic. These charts plot process measurements over time and include control limits that indicate when the process is behaving abnormally. For the call center example, an SPC chart tracking average handling time would have triggered alerts at Week 3 or 4, allowing for early intervention.
Control charts help distinguish between common cause variation (natural, random fluctuations) and special cause variation (assignable, non-random changes). When data points fall outside control limits or show non-random patterns like trends or runs, investigation and corrective action are required.
Establishing Standard Operating Procedures
Clear, detailed, and accessible standard operating procedures (SOPs) serve as the foundation for process stability. These documents should be living resources that are regularly reviewed and updated. They must be specific enough to ensure consistency yet flexible enough to accommodate necessary variations.
In our call center example, SOPs should detail exactly how calls should be handled, what resources to use, when to escalate, and how to document interactions. Regular audits comparing actual practice against SOPs help identify drift early.
Visual Management Systems
Visual management makes process performance visible to everyone involved. Dashboards, performance boards, and real-time displays keep teams informed about current process status relative to targets. When metrics are visible, teams naturally take ownership and respond more quickly to deviations.
A visual board in the call center showing daily metrics for handling time, satisfaction scores, and resolution rates helps agents and supervisors immediately recognize when performance is slipping, enabling rapid response.
Regular Training and Skill Refreshers
Human factors are among the most common sources of process drift. Regular training sessions, skill assessments, and refresher courses ensure that all team members maintain the competencies required for consistent process execution. New hire training should be standardized and comprehensive, while ongoing training addresses specific skill gaps or process updates.
Preventive Maintenance Schedules
For processes involving equipment and machinery, preventive maintenance is essential. Regular calibration, cleaning, and component replacement based on schedule rather than failure prevent equipment-related drift. Maintenance records should be reviewed to identify patterns that might indicate developing issues.
Control Plans
A comprehensive control plan documents what needs to be monitored, how often, by whom, and what actions to take when problems are detected. This living document serves as the roadmap for sustaining improvements. It should specify critical process parameters, measurement methods, sampling frequencies, control limits, and response protocols.
For the call center, the control plan would include daily monitoring of handling times, weekly satisfaction score reviews, monthly SOP audits, and quarterly comprehensive process assessments.
The Role of Leadership in Drift Prevention
Leadership commitment is perhaps the most critical element in preventing process drift. Leaders must allocate resources for monitoring activities, respond supportively when problems are identified, and resist the temptation to relax standards when short-term pressures arise.
Regular management reviews of control metrics demonstrate commitment and keep improvement top of mind. When leaders consistently ask about process performance and act on reported issues, teams understand that maintaining gains is a genuine priority.
Measuring the Success of Drift Prevention
Success in preventing process drift is measured by sustained process performance over extended periods. Key indicators include:
- Process capability indices remaining stable or improving
- Control chart data showing only common cause variation
- Defect rates remaining at or below target levels
- Customer satisfaction scores maintaining improvement levels
- Reduction in the number of corrective actions required
Returning to our call center example, successful drift prevention would show handling times remaining between 5.8 and 6.2 minutes, satisfaction scores consistently above 4.6, and resolution rates above 85% for extended periods.
Conclusion
Process drift prevention is not a one-time activity but an ongoing commitment to excellence. The Control Phase of Lean Six Sigma provides the tools, techniques, and mindset necessary to maintain improvements over time. By understanding the causes of drift, implementing robust monitoring systems, maintaining standards through documentation and training, and fostering a culture of continuous vigilance, organizations can ensure that their hard-won improvements deliver lasting value.
The investment in proper control mechanisms pays dividends through sustained quality, consistent customer satisfaction, and continued competitive advantage. While it requires discipline and resources, the cost of allowing drift to occur far exceeds the investment in prevention.
Enrol in Lean Six Sigma Training Today
Understanding process drift prevention is just one aspect of the comprehensive Lean Six Sigma methodology. Whether you are looking to advance your career, drive improvements in your organization, or develop systematic problem-solving skills, professional Lean Six Sigma training provides the knowledge and credentials you need. Our certified training programs cover all phases of DMAIC, including detailed instruction on Control Phase techniques, statistical tools, and real-world application. Do not let your organization’s improvements slip away due to process drift. Enrol in Lean Six Sigma training today and gain the expertise to implement lasting change. Visit our website to explore training options at Yellow Belt, Green Belt, and Black Belt levels, and take the first step toward becoming a recognized expert in quality management and continuous improvement.
