Does anyone know how it is possible to see a unilateral profile say a tolerance of 0.5mm but the die shop is trying to keep it at 0.25mm? CPK comes out bad while doing this due to a profile always sees nominal at zero. Tooling does not want to set it to zero due to it may drop out of spec and with it set to 0.25mm there will be wiggle room of ±0.25mm.
In order for process controls to be relevant to the specification, they need to reflect the drawing tolerance as communicated on the print... Anything else would be an invalid deviation from the print.
In my organization, they would make an internal drawing, and define the material-safe (or tightened tolerance) condition as you are describing, as an internal machining spec on the internal drawing.
Within PCDMIS, you simply need to shift the nominal value form zero, or produce a second dimensional tolerance control and label it as an internal tightened spec.
