Robust design of neutralization process of the residual electric charge on the surface of PP-films

Neutralization of the residual electrical charges at the surface of insulating materials is often a required operation in a multitude of industrial applications or laboratory techniques. The aim of this work is to evaluate the robustness of such a process, making use of Taguchi's methodology. The study was performed on polypropylene films (60 mm × 60 mm × 0.08 mm) that had been previously charged by exposing them for 10s to the negative DC corona discharge generated by a wire-grid-plate electrode system. Two of the four factors taken into consideration in the present study, namely the amplitude and frequency of the applied AC high voltage, were selected as "design factors" of the neutralization process. The other two, the relative speed and distance between the neutralizing electrode and the sample, were chosen as "noise factors". The results of the experiments show that the "design factors" have a very significant effect on the neutralization process. Of the two "noise factors", only the distance between the sample and the neutralizing electrode significantly influences the process. The calculation of the "signal/noise" ratio, according to Taguchi's methodology enabled the prediction of the robust design of the neutralization process: the applied high-voltage should have amplitude of 20 kV and a frequency of 50 Hz.