Most organizations are good at rallying around chronic problems and finding solutions. But long term discipline in sustaining those solutions is a different story – all too often a process will slowly return to its original state as the path of least resistance takes control in the manufacturing environment. This is where control plans come into play: control plans play a vital role in sustaining process improvements over the long run.
What is a Control Plan?
Control plans are typically Excel documents that list the product and process characteristics that must be monitored during the manufacturing process, including measurement methods and necessary reaction plans for deviant conditions. Control plans come in a variety of formats, and the most popular is the Excel format see dmaictools.com for control plan templates.
Without control plans, most processes will gradually drift into a state of disrepair due to employee turnover, knowledge loss, and short-term production priorities.
What Makes an Effective Control Plan?
1. Clear Product Specifications
Product specifications are clearly defined and linked to customer requirements.
A PFMEA (Process Failure Modes and Effects Analysis) has been conducted on all process steps, and the team fully understands the quality risks associated with each step.
3. Effective Measurement Methods and Reaction Plans
Process and product measurement methods must be clearly defined and repeatable.
4. Internal Audit
Internal audit is essential for maintaining control plan discipline. Effective internal audit programs include a few key elements –
- An underlying SOP (standard operating procedure) that states control plan responsibilities such as maintaining and following control plans. Process engineers typically publish and maintain control plans.
- An internal audit calendar that shows which production areas will be audited at specific times throughout the year.
- Management review of audit findings. Management must review audit findings and address them – this activity is extremely important and will strengthen control plan discipline in the facility.
The Real Key to Process Control
Preventing defects at the point of origin is the most efficient form of process control. This is known as error proofing, which means that a defective condition cannot be created in the first place. One example is the larger diameter nozzle found on diesel pumps, which will not fit into a standard size gas tank opening. In this case, the defect of putting the wrong gas in the car cannot occur to begin with. Another error-proofing example is a conveyor curing oven that will stop automatically and sound an alarm if the oven temperature falls outside a predefined window. In this case, the defective condition of an uncured product cannot occur because the oven stops and an alarm sounds before uncured product can be produced.