Injection moulds for the production of caps for water and soft drink bottles are compact high-performance systems with exacting requirements in terms of output, production safety, quality, and reliability. SCHÖTTLI collet chuck moulds allow maximum freedom of cap design and geometry and produce screw caps that meet particular quality requirements with a high output rate and low maintenance. During demoulding, collet chucks ensure that all bridges that connect to the tamper-evident band (TE) are removed from the mould in a geometrically identical manner. This approach offers benefits for contract bottling companies as well as for consumers.
In contrast to the demoulding with slider technology, collet chucks open in all directions to remove the bridges that connect to the tamper-evident band. For cleaning, each collet chuck can be individually removed from and restored to the installed mould.
Photo by SCHÖTTLI AG
The constant and even geometry of bridges across the diameter of screw caps offers several benefits: this approach allows a virtually uninterrupted capping operation at the filling line as the tamper-evident band is evenly distended during capping. During this process, all connecting bridges are subjected to an identical load, so that weak connections are not torn during capping. This is particularly important for an error-free filling operation.
Consumers also benefit from even bridges: when the screw cap is opened for the first time, the tamper-evident band tears evenly. This homogeneous opening behaviour provides maximum protection from manipulation, which ensures consumers that they are enjoying a high-quality product from safe packaging.
Increasing number of cavities
Increasingly lightweight, i.e. thinner caps call for increasingly close tolerances. These requirements can only be met by 100% process-safe production resources, i.e. a finely-tuned injection moulding system consisting of mould and injection moulding machine, which allow a high output rate, maximum repeatability and dimensional stability. Integrated camera monitoring systems used for optical inspection prevent the supply of defective caps, which are produced with a reject rate of virtually nil.
The requirements concerning quality and cost-efficiency of production resources are expected to become even more exacting. While 48-cavity moulds were on the leading edge only a few years ago, cap production with 96-cavity moulds is now state-of-the-art.
Major Chinese bottling specialist operates with 96-cavity collet chuck moulds
One of the largest mineral water bottler in the Chinese market is a typical example of the current trend for an ever-increasing number of cavities in a mould. The company has been part of SCHÖTTLI’s stock of customers for many years and initially acquired a range of 48-cavity systems for the production of type 30/25 caps for non-carbonated mineral water. Recently, SCHÖTTLI supplied its customer with more than 10 high-performance moulds for the production of these lightweight caps with a weight of less than 2 g – all of them with 96-cavities.
Again, these orders show that SCHÖTTLI collet chuck moulds reliably deliver high-quality caps – particularly in direct comparison with compression moulds or traditional slider technology.
Collet chuck better than slitting
Particularly in contrast to compression-moulding processes, injection moulding with collet chuck technology delivers a significantly higher product quality as it dispenses with the time-consuming slitting of the TE-band. During this process, which takes place after production, the individual screw caps are routed past cutting knives that are rotating at high speed, in order to partially cut open the closed TE-Band. The success or failure of slitting depends on the quality of the knife, i.e. the sharpness of its edges and the cutting depth.
| Stefan Gaul, Product Manager Packaging Doris Anderegg, Marketing Tel. +41 52 646 2222 Fax +41 52 657 3532 |
