Sacmi’s grid-type inspection system is a formula plus patented technology to identify, via a simple algorithm, preform defects that would otherwise be invisible to the human eye, detecting them easily, economically and above all without any risk of encountering the errors induced by the image interpretation that is necessary on traditional inspection systems which use polarized light. This innovative Sacmi-developed grid-type inspection system can be installed on the entire PET preform vision system range, on both production lines (PVS 003 and PVS 024) and in test labs (PVS 2).
Traditional inspection techniques that use backlighting with a polarizer placed immediately behind the product make it difficult to execute easy, economic detection of major defects caused by, for example, on-resin stress during the cooling process and or water in the moulds – the so-called watermark. These defects, in fact, generate patterns that then need to be interpreted by the operators; this requires skill and experience as the faults are tricky to translate into inspection algorithms which can be used by a vision system.
This is where the new Sacmi system comes into play – the polarized light has beenreplaced with a special patented back lighting unit that projects gridlines behind the preform. On flawless preforms the result is a series of straight parallel lines; on faulty areas, instead, these become wavy. Using the grid, even small defects are immediately identifiable.
The new patented Sacmi methodology is available as an option on the complete PVS range, thus allowing completion of the standard checks used to analyze defects on the entire preform, body finish and bottom. This gives the preform quality control department a significant boost as it permits an extremely economic, perfect preform X-ray to be made that is error-free (some defects analyzed using the polarized light method can escape even the most expert eye).
The PVS range will be exhibited at Sacmi on15September 2015 during the Food& Beverage Plastic Day, a special event organized to show customers and partners the latest technological innovations in plastic containers and closures for the food and beverage markets.
