What factors affect the molding of bottle cap molds

Update: 13-01-2022

High cavitation mould tools are common flip cap mould place in closure production, due to the high volumes required. 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 consequently 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 maybe 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  Demag continues to pioneer the development of packaging machines.


The company’s El-Exis SP range, available globally, now comprises 10 machines, with a clamp force range of between 150and 1,000 tons.Capable of delivering dry cycle times of less than two seconds, this latest generation of  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 1000 ton 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 that previous generations of El-Exis machines.


Reducing the cavitation of a tool to 64or 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 dedicatedIntElect all electric machine cells in recent years as they deliver consistent moulding precision. Additionally, the newest IntElect’s feature an increased tie bar distance which significantly increases the mould space. This means they can accommodate larger mould tools combined with very small injection units. The ability to install small screws matched with a large mould space is a big advantage as it improves 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. Extra tests may need to be performed to ensure shrinkage doesn’t 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 conditions.An automated example was showcased at last years’ K Show. Featuring the inspection Capwatcher Q Line from Intravis, eight high-resolution cameras collect, visualise and provide up to 144,000 cavity-based measurements per minute. It also sources a unique inline temperature measurement for each closure, which allows moulders to determine the shrinkage behaviour of each and every closure. From a quality control perspective, this is groundbreaking stuff and significantly reduces production waste.

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