Challenge test of an Automatic Machine for the Non-Destructive Detection of Integrity Defects in Blister Containers

CCIT test

The preliminary model calculation, was executed by using containers from Set N. Each of these containers, underwent 32 successive tests, thus determining the conformity range. The deflections average values μ_ij and standard deviation Δ_ij, were then calculated for each C_ij cell, as well as the maximum (THR+) and minimum (THR-) thresholds. This phase, allowed to determine both the best parameter setting for the time periods of the various phases (T_z z=1..4) and the reference value (K) for calculating the results of CCIT.

Specifically, the information derived from carrying out the model calculation, indicated the need to set K = 2.5.

Subsequently, it was decided to conduct four distinct analyses, varying the total cycle time, T₀. After identifying the suitable vacuum level conditions (congruent with the need to maintain the quality of the lid and not generate further integrity defects) and the relevant time periods for vacuum generation, change and maintenance, only the time required for stabilization (T₂) was varied. Therefore, all other times were kept constant, except for the F03 recipe in which, in addition to T₂, the T₃  time was reduced (Table B).

Each of the analyses, was carried out within one day, taking into account a set of specific recipe parameters, respectively.

Table B. Recipes

Ten CCIT cycles, were then carried out in a round-robin sequence, for each container relating to each of the P sets involved. The round-robin method, was selected to ensure that a time interval of more than five minutes was left between two successive CCIT cycles on the same container. This made it possible, for each container examined, to reestablish the relative nominal conditions to precede the next reuse, in other words the recovery of lid deflection induced by the vacuum during the CCIT cycle.

The determination of the results, was then conditioned by the following rules:

1. the failure to detect a defect represents a false negative
2. the detection of a defect in a C_ij cell without a hole represents a false positive
3. the detection of a defect in a C_ij cell without a hole, that is 100% systematic in subsequent tests, is not considered a false positive. It is assumed that, if a defect is detected in a generic, non-drilled C_ij cell in all CCIT cycles specified, it is truly defective.  This behavior, was observed in the P_15 set in which two non-drilled C_ij cells produced non-conforming results
4. notwithstanding the details of the previous point, the “false positives” indicator is the sum of the individual C_ij cells for which a non-conforming result is obtained in each individual CCIT cycle.

Summary of results

The results of the four distinct analyses carried out, are given in the following tables, ordered according to the CCIT cycle time:

Table C – T₀ = 60 sec.

Table D – T₀ = 30 sec.

Table E – T₀ = 20 sec.

Table F – T₀ = 10 sec.

Table C. Report of results for the F04 recipe

Table D. Report of results for the F01 recipe

Table E. Report of results for the F02 recipe

Table F. Report of results for the F03 recipe

It is deduced that:

increasing the length of the cycle, and specifically increasing T₂, gives the following results:

• a decrease in false negatives, in general a longer test period allows better detection of defects
• an increase in false positives

increasing the diameter of the hole gives the following results:

• an increase in the Sigma level and therefore in the reliability of the defect detection process.

Having considered the worst case scenario, in the context of implementing positive controls, in other words, having used containers for which the defect is positioned adjacent S_ACQ when performing CCIT, implies that the performance of the measuring system can be greater than those resulted in the case study.