The measure that best represents the degree of treatment achieved is "watt density" (WD) expressed in [W*min/m2] whose basic parameters are:
- the power supplied by the generator
- the line speed
- the number of discharge electrodes.
Given that materials or surfaces react differently to corona treatment, it is the task of the film manufacturer to associate the dyne/cm level achieved by a given plastic film with a given Discharge Density.
The adjustment of the set power can be manual, depending on the rotation speed of the discharge roller and depending on the set watt density (sWD).
The corona treatment process is controlled in three phases:
- "In line" recording of processing data on SD flash memory card to be installed in each corona generator.
- Recovery of recordings by removing the SD card from the generator and copying its contents to a PC.
- Display, organisation, calculation and printing of processing data recorded in the generators through the Corona Quality Control software to be installed in the PC.
The Corona Quality Control software enables:
- creation of graphics reporting the progress of fundamental production measures, events occurred (alarms, faults...) and functional changes
- filing of reels produced by adding processing data
- identification of reel sections (based on time) in which the power supplied (or the WD) deviates from the set power (or the sWD) and the supply of valuable data for the evaluation of the uniformity of the corona treatment.
The numerous data visible in the Graphics include: Power set, Power supplied, Watt Density set, Watt Density supplied, discharge roller speed and quantity of discharge electrodes set in the generator.