What is a Six Sigma Control Plan?

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Six Sigma Control Plan

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What is a Six Sigma Control Plan?

A Lean Six Sigma control plan is a detailed written description of the process. It outlines the steps that must be taken to keep a process or device running at its current level of performance. Control plans provide a detailed description of each step and the parameters that must be monitored to avoid deviations or variations from the mean performance of a batch of products.

A Lean Six Sigma control plan consists of two segments

  • Process monitoring is a tool called a process summary. This summary allows visibility, review, and action on all important process outputs within an organization.
  • Process control uses a tool called process control plan. This plan creates feedback loops and takes actions to ensure that the process is under constant control. A good process control plan allows you to change equipment, materials, information, or throughput rates without affecting the quality of the process.

The Process Management Summary

The process management summary is used to gather all critical-to-quality outputs (or CTQs) for a process or department, division, or entire company. The summary can be rolled up to any level required by your company for monitoring, reviewing, and taking actions to ensure acceptable business performance and process quality. Add the Lean Six Sigma project’s CTQs each time you complete it to your summary. The administrative section of this summary is used to identify the organizational areas that are being discussed, as well as the revision level and the date. The main body is where the summary’s purpose is captured. It provides enough information to allow anyone to easily see the status and how they relate to downstream processes.

The Process Control Plan

The process control plan serves as a companion to the process management summary. The process control plan helps you to concentrate on the Xs, the inputs to your process. The inputs are defined in the formula Y = f(x). These are the crucial Xs determined by the Lean Six Sigma project. You can also place the (CTQs) on a process control program.

The process control plan, when done properly, creates a complete picture that includes all inputs, outputs, and activities for a single process.

What’s the purpose of a Six Sigma Control Plan and how can it help you? The purpose of the control phase of the DMAIC roadmap is to ensure that performance improvements made by the project group are sustained over time. A Control Plan is basically a summary of all information pertinent to control the improved process.

Why use a Control Plan?

A Lean Six Sigma Control Plan is a single reference point for understanding the process’s characteristics, specifications, and standard operating procedures (or SOPs) for the process. The Control Plan can be used to assign responsibility and allocate accountability for each activity in the process. This allows for smooth execution and long-term sustainability.

A well-designed control plan can help the business avoid negative business effects from process flaws or process deterioration. It also helps product and process owners track and correct the performance of Key Performance Input Variables (KPIVs) and Key Performance Output Variables (KPOVs).

What to know before developing the Control Plan

Lean Six Sigma Control Plans are crucial to decision-making and should be prepared after careful consideration and assessment of the project’s product status from all angles.  These attributes must be considered before the project can begin.

  1. Input and Output: It is essential to determine the various IO parameters as well as the stages at which they enter exit Control Process. This will ensure a free flow of control information, which is vital to the project’s success.
  2. Specifications and Measurements: A Control Plan should be developed after careful analysis of customer perceptions and expectations. This ensures that the final product/service meets the customer’s specifications.
  3. Reporting and Sampling Frequency: Having a set schedule allows for adequate time to correct any errors. Regular reviews allow for tighter control and monitoring.
  4. Process Design and Execution – The Control Plan is built around the central process. It is created by determining the appropriate standards and setting performance criteria.
  5. Corrective Measures: Any Control Plan should include a framework for implementing corrective actions.
  6. Process Owner Identification and Documentation: Process owners refer to the persons or groups of people who are responsible for and have the authority to make any changes to the process during a project’s progress. It is crucial to identify Process Owners early in order to establish accountability.
  7. Recording – It is essential to document information at all stages of a project in order to facilitate planning, testing, implementation, and assessment. To record and store information about a product or process, plan sheets are used.

An example

How to structure

A Lean Six Sigma Control Plan can include as many or few items as necessary to meet the requirements of the project or process being considered. The following are some examples of Control Plan items:

  • The Critical to Quality Characteristics (CTQ) – These are the key quantitative and measurable characteristics of a product/process whose performance limits or specifications must be met to satisfy customers. This allows you to align design specifications with customer needs.
  • Process Flowchart Many Control Plans include a visual representation that shows the process flow with key decision-making steps highlighted. This provides a high-level overview of all stages and stakeholders for quick and easy reference.
  • Specification Characteristic: To quantify a CTQ, a product characteristic must be identified. This column records the characteristic of a specification. 
  • Process Step: This column contains the name or label for the step of the process. 
  • Measurement Method: This column can be used to describe the method used to measure
  • Specifications This item can be used to record both the numerical values and the unit of measurement. 
  • Frequency of Measurement: Indicates the frequency at which samples are selected for measurement.
  • Sample Size: Indicates how large the sample is to be measured.
  • Corrective Action: All corrective actions taken at that step are documented and recorded for future reference.
  • Additional documentation: These fields may include the name of the person who took the measurement, the date, time, and place at which it was taken, revision number, version control, and location.
  • Standards – For manufacturing operations and control planning used in businesses, the quality standard and SOP (Standard Operating Procedures) guidelines may be recorded.

In Conclusion

The Lean Six Sigma control plan, when done properly, creates a complete picture that includes all inputs, outputs, and activities for a single process. The control plan is critical to be a focal point for the control of the improved process.

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