The following steps can be used in developing a control plan. As a preparation step, ensure that all process steps and quality risks are accounted for by completing a PFD (Process Flow Diagram) and PFMEA (Process Failure Modes & Effects Analysis).
Section 1 – Basic Part and Supplier Information
This section is self explanatory, and includes details like the part number, supplier or plant name, contact information, and approval dates (click on the image for a larger view).
Section 2 – Process Steps and Supporting Tools / Equipment
- The first column typically lists out each step in the order that the manufacturing process takes place – these numbers should match up with the process steps in the PFD and PFMEA.
- The second column is a clear description of each process step.
- The third column lists any special equipment needed to complete the process step.
- The first column is a unique identifying number for the characteristic being inspected or controlled.
- If the characteristic is measured on the product itself, the second column is filled in with the characteristic’s description, otherwise it is left blank.
- If the characteristic is part of the process (i.e. drive torque on a screwdriver), the third column is filled in with the characteristic’s description, otherwise it is left blank.
- If the characteristic is a CTQ (Critical to Quality feature), a Y is noted in the fourth column.
Section 4 – Control Methods
- The first column lists the specification and tolerance for each characteristic.
- The second column clearly describes the measurement method.
- If sampling inspection is used as the control method, the Sample Size column is the subgroup size for each sample, so a sample size of 5 indicates that 5 parts must be pulled and measured (or 5 process readings must be taken). This is a common approach when samples are pulled for control charts.
- The Sample Frequency column reflects how often a subgroup of readings must be taken.
- The Control Method lists the means by which the characteristic is controlled. Error proofing is far more effective than sampling inspection.
- The Reaction Plan column shows how the associate running the process must react if a deviant condition is observed.
Control plans must be kept updated as changes are made, and should be audited as part of the Quality Management System (QMS).