Six Sigma DMAIC Process - Control Phase - What is a Process Control?
A control mechanism that ensures that the process performance be maintained are at level that satisfies the customer’s need and drive the ongoing improvement of process performance. The key elements that constitute a process control system are
Documentation of the process
Develop process metrics
Monitor the process based on the defined metrics
When we talk of a process is operating "In-Control" it translates to a situation that only common cause variation is present, process is predictable and process is stable.
Control limit Vs Specification limit Control Limits: It is defined based on process performance. It help determine if the process is “in control”. It is plotted on control charts and it changes when there is a verified, significant change to the process.
Specification Limits: It is provided by the customer part of SLA. It help determine if the process is producing defects. It is not plotted on control charts and it changes when requirement comes from the customer.