Controlling a process means managing the variations that occur over time. Indeed, while the process is in use, various factors such as tool wear, material modifications and operator changes can influence its state. This inevitable dynamic has an impact on the centering and variability of the process. That's why it's crucial to adjust the process at the start of production to get as close as possible to the target.
Control cards are used to fine-tune the machine by monitoring the evolution of the process over time. They enable rapid reaction in the event of deviations in centering or dispersion.
When calibrating a process, it is important to avoid two pitfalls:
- Over-adjustment: This occurs when the process is adjusted too frequently. In other words, trying to center the process does not guarantee that all parts must be exactly on target, due to the dispersion inherent in the process.
- Process drift: The process under control can drift over time due to a variety of specific factors, such as tool wear, operator changes or process interventions. It is essential to detect any drift and refocus the process accordingly.
Example of control cards with the software Ellistat Data Analysis :
