The control phase is the final phase of the DMAIC (Define, Measure, Analyze, Improve, Control) process in lean Six Sigma. This phase focuses on ensuring that the improvements made during the previous phases are sustained and that the process is under control. The control phase involves developing a plan to monitor the process, identifying potential issues, and implementing controls to prevent the recurrence of defects. In this article, we will provide a detailed overview of the control phase in DMAIC.

Objectives of the Control Phase

The control phase has two main objectives:

a. To ensure that the improvements made during the Improve phase are sustained

b. To ensure that the process is under control and that defects do not recur

To achieve these objectives, the following activities are typically undertaken during the control phase:

a. Developing a process control plan

b. Implementing controls to prevent the recurrence of defects

c. Establishing a monitoring system to track key process metrics

d. Identifying potential issues and developing contingency plans

e. Communicating the results of the improvement effort to stakeholders

Developing a Process Control Plan

The first step in the control phase is to develop a process control plan. This plan outlines the steps that will be taken to monitor the process and ensure that it remains under control. The process control plan typically includes the following elements:

a. Process Control Charts: A process control chart is a visual representation of the process over time. It shows the upper and lower control limits, which represent the range of variation that is acceptable for the process.

b. Control Limits: Control limits are used to define the range of variation that is acceptable for the process. The upper control limit (UCL) and lower control limit (LCL) are calculated based on the data collected during the Measure phase.

c. Sampling Plan: The sampling plan outlines the frequency and method of data collection. It identifies the key process metrics that will be tracked and the frequency at which they will be monitored.

d. Response Plan: The response plan outlines the steps that will be taken if the process goes out of control. It identifies the individuals responsible for taking action and the specific steps that will be taken to bring the process back under control.

Implementing Controls to Prevent the Recurrence of Defects

The next step in the control phase is to implement controls to prevent the recurrence of defects. This involves identifying the root causes of defects and developing controls to prevent them from recurring. The following are some of the common controls that can be implemented:

a. Standard Operating Procedures (SOPs): SOPs are written instructions that describe how a particular process should be performed. They ensure that the process is performed consistently and that defects are prevented.

b. Training: Training is provided to employees to ensure that they have the knowledge and skills required to perform their job correctly.

c. Mistake-Proofing: Mistake-proofing involves modifying the process or the product to prevent defects from occurring. This can include things like redesigning the product to make it easier to assemble or incorporating sensors to detect defects.

d. Visual Management: Visual management involves using visual cues to communicate information about the process. This can include things like visual controls, such as signs and labels, to ensure that the process is performed correctly.

Establishing a Monitoring System

Once the controls have been implemented, the next step is to establish a monitoring system to track key process metrics. This involves collecting data on a regular basis and using this data to evaluate the performance of the process. The monitoring system should be based on the process control plan developed earlier in the control phase.

The data collected should be analyzed using statistical tools to identify trends and patterns. If the data suggests that the process is going out of control, the response plan developed in the process control plan should be implemented to bring the process back under control.

Identifying Potential Issues and Developing Contingency Plans

Despite the best efforts to implement controls and establish a monitoring system, issues can still arise. It is important to identify potential issues and develop contingency plans to address them. The following are some of the common potential issues that can occur:

a. Changes in the Process: Any changes made to the process can impact its performance. It is important to ensure that the changes are thoroughly tested and evaluated before they are implemented.

b. Employee Turnover: Employee turnover can impact the performance of the process. It is important to ensure that new employees are properly trained and that the process is documented to ensure consistency.

c. Equipment Failure: Equipment failure can cause defects in the process. It is important to have a maintenance plan in place to ensure that equipment is regularly inspected and maintained.

d. Supplier Issues: Supplier issues can impact the quality of the inputs to the process. It is important to work with suppliers to ensure that they meet the required quality standards.

Communicating the Results of the Improvement Effort to Stakeholders

The final step in the control phase is to communicate the results of the improvement effort to stakeholders. This involves sharing the data collected during the monitoring process and the results of any corrective actions taken. The following are some of the stakeholders that should be informed:

a. Management: Management should be informed of the results of the improvement effort and the ongoing performance of the process.

b. Employees: Employees should be informed of the changes made to the process and the impact on their roles and responsibilities.

c. Customers: Customers should be informed of the improvements made to the process and the impact on the quality of the product or service.

d. Suppliers: Suppliers should be informed of any changes made to the process that may impact their inputs.

Conclusion

The control phase is a critical phase in the DMAIC process. It ensures that the improvements made during the previous phases are sustained and that the process remains under control. The control phase involves developing a process control plan, implementing controls to prevent the recurrence of defects, establishing a monitoring system, identifying potential issues, and communicating the results of the improvement effort to stakeholders. By effectively implementing the control phase, organizations can ensure that the improvements made during the DMAIC process are sustained, and that they achieve long-lasting benefits.