CAPS AND CLOSURES | INNOVATION


high volumes required. Flowers says that adding the tether ring into the mould design either means reducing the number of cavities in the tooling or increasing the size of the mould tool and conse- quently the mould space and tonnage of injection moulding machine to accommodate bigger tooling. Additionally, if the shot weight and part weight of the closure component increases, a greater injection unit capacity may be required. The machine selected will be dictated by mould design and the cavitation layout. Higher pressures and speeds, faster cooling times, and modifications to part-ejection and gating arrangements are all important factors to keep in mind. To support these efforts, Sumitomo (SHI) Demag continues to develop its packaging machines. The company’s El-Exis SP range, available globally, now comprises ten machines, with a clamp force range of between 150 and 1,000 tonnes. Capable of delivering dry cycle times of less than 2s, the company adds that this latest generation of EL-Exis SP machines is specifically designed to withstand the higher stresses and injection pressures that are so critical in achieving repeatability. The range is aimed squarely at high volume manufacturers of polymer products, particularly caps and closures, and the new 1,000-tonne machine can easily accommodate a 96-cavity tether cap and ring tool. With the introduction of a new control valve regulating the hydraulic pressure during the loading of the accumulator, the range consumes up to 15% less energy than previous generations of El-Exis machines. The company adds that reducing the cavitation


of a tool to 64 or less might warrant closure moulders considering the efficiency and energy saving merits of an all-electric machine. Several closure moulders developing tamper-evident closure bands have invested in dedicated IntElect all electric machine cells in recent years as they deliver consistent moulding precision. Additionally, the newest IntElects feature an increased tie bar distance which significantly increases the mould space. This means they can accommodate larger mould tools combined with small injection units. The ability to install small screws matched with a


large mould space is a big advantage as it im- proves the dosing and injection performance. “Processing consistently is equally important to the integrity of the tether ring which slides over the neck thread of a beverage container,” adds Flowers. “Extra tests may need to be performed to ensure shrinkage does not occur, or conversely the tethered cap ring stays attached to the bottle. An integrated vision control system is more than capable of monitoring these processing condi- tions. An automated example was showcased at the last K Show. Featuring the inspection Cap- watcher Q Line from Intravis, eight high-resolution cameras collected, visualised and provided up to 144,000 cavity-based measurements per minute. It also sourced a unique inline temperature measure- ment for each closure, which allows moulders to determine the shrinkage behaviour of each and every closure. From a quality control perspective, this is ground-breaking stuff and significantly reduces production waste.” HTS IC has developed conformal cooled gate


inserts for injection moulding in combination with water distribution plates and hot runner manifolds that can significantly reduce cycle times and warpage in the injection moulding of caps and closures. “In caps and closures, continuous light- weighting is resulting in increased pressure to decrease cycle times and optimise cooling rates,” says Primož Maraž, Head of R&D. “In some cases, this means that cycle times have already dropped under 2s. Maintaining these short cycles, while ensuring moulded part quality is a challenge for the whole value chain – from moulders and injection moulding machine manufacturers to toolmakers and resin suppliers. Effective thermal management of mould and gating system components is often the key to meet both cycle time requirements and the dimensional and surface quality of moulded parts. Conformally cooled parts are known for better thermal management properties, therefore their use is gaining popularity. Most often these parts are Powder Bed Fusion [PBF] 3D printed. However, technological advancements over the last decade have made it possible to develop and produce conformally cooled components with


Left: ITherm single gate insert and iTherm


multiple gate insert from HTS


www.injectionworld.com April 2021 | INJECTION WORLD 41


IMAGE: HTS


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