Question
My question is about sampling aluminium foils, films used in packaging and sticker labels received in rolls which are wound around a core. I can decide to chose the number of rolls to sample from using the tables given in Z1.4, but how should I decide on the amount of stickers and aluminium foil and film to be sampled? I ask this question since it is practically impossible to sample from within a wound roll.
Answer
The ANSI Z1.4 and Z1.9 standards might be applicable when all units do not have the same probability of being selected. Since you cannot sample units closer to the core, and defects would never be detected unless they occur at the end of the roll, I would recommend a different strategy, either using a vision system (100% inspection) or in process inspection.
If you want to use the standard, the sample size should be based on the number of samples, not the number of rolls. For example, a roll with 5000 labels would be an N=5000 not N=1.
For more on this topic, please visit ASQ’s website.
Thank you. This should help me design my sampling plan.