When the author started at Q-DAS 19 years ago, there was only one possible requirement in the oldest version still supported at the time (16-bit versions). The capability index. These coloured the "smiley".
At that time, however, working with databases was almost unknown. Only those characteristics that were to be evaluated according to C values were evaluated in qs-STAT. A small file in DFQ format, perhaps created by copy/paste from Excel.
Over the years, the data send for evaluation to the Q-DAS software grew rapidly. Additionally, next to the “characteristics of the SPC”, 100% measurements, process parameters, auxiliary characteristics and others were introduced in our software. Furthermore, the possibilities of evaluation by the qs-STAT were no longer purely limited to the evaluation of capability. Thus the “overall evaluation” based not only on the capability indices but also on other requirements was developed in the heart of our software.
There will be a new Q-DAS strategy with the name "Q-DAS Process Capability (05/2024)". Some of the options described here will be activated in this strategy.
The standard requirements of the Q-DAS Strategy are the C-Values and (just for the sake of completeness) if values are outside of the specification limits:
The target values are 1,33 (except for the characteristic class “unimportant”, where the targets have set to be just 1,00, just to tell our customers how important is to take care about the 5 different characteristic classes and what they can handle do with them). The target values are used when 125 values are in calculation. The less measured values dataset have, the more the target value for capability indices will be automatically adapted based on the confidence-interval (down to 10 values).
In addition to these classic requirements, the following sub-chapters describe various requirements that occur in the industry. The following pages do not describe in detail how to set up these specific requirements. This is described in the general manual of the evaluation strategy and must be discussed again with an application engineer in the workshop.