Understanding the roll-on-pilfer-proof process

There is a requirement (within the food packaging industry) for a greater analytical knowledge and more scientific understanding of the ROPP capping process and of the interaction of caps (closures) with the threaded part of the glass container (finish). Threads used within the industry have largely developed empirically from metal thread profiles. An improved understanding is needed so that problems associated with that process can be better understood and solved. Such problems can be manifest in damaged closures, ‘spinners’ and closures that are just too difficult to open. The term ‘spinners’ is used for closures that do not break the pilfer band (a tamper evident safety feature) when twisted. The same term is also used to describe closures that have been turned the wrong way (i.e. clockwise) on opening, stripping the thread whilst not breaking the pilfer band. To combat this problem it is desirable to produce a closure system that has a high torque when twisted in the wrong direction (known as the over torque) whilst maintaining good seal integrity and a low torque for correct opening procedure. A successful feasibility study was carried out to investigate the appropriateness of using finite element techniques to investigate closure systems and gain the required understanding to improve these systems. The follow on project utilised these finite element techniques and experimental testing using a single-head capping machine. The Project focuses on the industry standard glass thread finish called the GF305 that utilises an extra deep, aluminium ROPP closure. The results of this work so far are presented here.