This analysis characterized a batch process for production of inkjet ink to meet the pH specification for various ink products. Since the nominal pH target for different inks, while manufactured by the same process were not the same, the deviation from target pH was analyzed. Results display a manufacturing process that is stable – thus in a state of statistical control.
The capability of the process with Cpk = 1.42 indicates that the specifications of +/- 1.0 pH unit are achieved with this process with very remote opportunity for production of non-conforming product. Furthermore, as the process is fairly well centered within specification limits, there is ample room for the process to drift up or down while still producing a quality product.