A control plan is a written document created to ensure processes are producing products or services that meet or exceed customer requirements at all times. It is a living document that gets updated as the organization gets process experience or receives customer feedback.
A control plan is a systematic approach to finding and resolving out-of-control conditions. It provides employees a guide to follow when troubleshooting a process through its documented reaction plan. It should provide a strategy to reduce process tampering, provide a vehicle to initiate kaizen events, and documented maintenance requirements.
A control plan complements standard work and is an extension of the control column in a design or process failure mode and effects analysis (DFMEA and PFMEA). It identifies the critical inputs (KPIVs) and outputs (KPOVs) variables and the activities that must be performed to maintain control of the variation related to the 6Ms (Man, Machine, Material, Method, Measurement, & Mother Nature) of processes, products, and services in order to minimize deviation from their preferred values.
There are seven attributes to consider when creating a control plan:
- Measurement and specifications. This includes defining those quality features important to your customer, determining how to measure those features, and setting up quality standards, and forming controls for the standards produced.
- Process inputs/outputs. This will involve providing an appropriate input/output range of performance for the critical variables, including how these variables will be measured, recorded, monitored, and the actions to be taken when out-of-control.
- Processes involved. A control plan is used to address the needs of vital processes, i.e., those that involve important customer requirements. The challenge is to define a precise set of standards that can be used to track performance.
- Sampling and reporting frequency. The frequency of taking samples depends on the time it takes to implement any corrective actions that may be required. Other considerations include the size of the sample and the correct sampling technique to be used.
- Recording information. The information on a control plan must be well documented. Check sheets and data collection sheets for different products and services may need to be created to facilitate this activity. A central repository is needed to store this information.
- Corrective action. Corrective action is the response to problems that are detected and may include fixing the problem or modifying the systems to prevent reoccurrence.
- Process owner. Every process should have an owner, that is, the person responsible to ensure that the process is controlled, monitored, and if corrective action is required, that it is implemented timely and is effective.
Other quality tools that support control plan development include:
- Voice of the customer (VOC)
- Voice of the process (VOP)
- Process mapping
- SIPOC
- IPO diagram
- DFMEA
- PFMEA
- Measurement system analysis (MSA)
- Attribute agreement analysis
- Check sheets
- Data collection forms
- Operational definitions
- Standard work
- Standard operating procedures (SOP)
- Error proofing, mistake proofing, or Poke Yoke
- Control charts
- Kaizen events
- Six Sigma DMAIC and DFSS
A control plan can be developed for any product or service, whether it be a manufacturing or transactional process. Below is a common format that is typically used.
