Control Plan
A control plan is a documented, process-specific control system that defines required inspections, measurements, and reaction actions at each manufacturing step to keep product and process variation within requirements. Built from the process flow diagram and PFMEA, it manages manufactured, purchased, and inventory parts through specified characteristics, tolerances, sampling methods, and escalation procedures.
On the shop floor, the control plan directs operators on which critical characteristics or process parameters must be checked at each operation, how often to check them, with what tool, and what action to take when a result falls out of spec. In warehousing and receiving, it specifies incoming inspection criteria for raw materials and purchased parts, including sampling plans, supplier document verification, lot identification, and quarantine rules for suspect material. For raw-material tracking, the control plan supports traceability by linking material lots to process steps and required records, helping isolate nonconforming material before it is consumed downstream. In high-mix manufacturing, it serves as the control backbone that prevents variation from propagating from incoming stock, kitting, WIP, and final assembly into shipped product.
Is a control plan the same as an SOP or work instruction?
No. A SOP or work instruction explains how to perform the job, while a control plan specifies what must be controlled, how to measure it, how often to check it, and what to do when the result is out of tolerance.
Does a control plan apply to purchased material?
Yes. Control-plan systems can cover manufactured, purchased, and inventory parts, so supplier receiving inspection and raw-material verification are valid control-plan elements.
What is the link between a control plan and traceability?
Control plans often include traceability information so variation can be tied back to specific lots, processes, or product hierarchies for containment and root-cause analysis.