Maximum output with minimal maintenance effort – the award-winning solution
Fully automated in-mold labelling with stack mold for hinged lids
With a fully automated production line for hinged lids for wet wipe dispenser boxes the English packaging manufacturer Amaray was awarded with the last years UK Packaging Award for the “Investment Project of the year”. The solution, which is unique in Europe, increases productivity, fulfills the very limited space regulations and minimizes the maintenance effort significantly. The production comprises a 12+12 stack mold with in-mold labelling, the fully automated removal with visual 100% laser inspection of the parts, as well as the packaging of the stacks. The design, layout and construction of the sophisticated stack mold was crafted by roth mold + automation, the customized valve gate hot runner system was supplied by EWIKON.
The one-piece hinged lid made of PP is injected and labelled in a single operation. A linear handling system per parting line positions the labels precisely and within fractions of a second in the cavity, removes the finished parts after the injection process and closes them. The type and size of the injection molding machine and thus the maximum possible mold dimensions and weights were defined very precisely by the customer. A maximum productivity at extremely limited space requirements demanded for a 12+12-cavity stack mold solution.
100 square meter (1076 sq ft) facility: Sumitomo Demag Elexis with a clamping force of 580 tonnes
Highly compact mold size: mold installation height of 1250 mm (4,1 ft)
A special set-up concept, as the mold is just 4 mm (0,01 ft) smaller than the clear width between the machine tie bars
A strict modular design with special plug connections for the electrical links between the plates, ensures optimum dismantling and ease of maintenance.
Additional weight restrictions due to limited crane capacities at the production site, required a total mold weight of 12 tonnes, whereby 8 tonnes could be allotted to the central block with hot runner system.
"It was most important that the mold weight was not reduced at the expense of mold stability. Here EWIKON was able to support us with a special manifold design. The element technology used allows a very compact, fully balanced flow channel layout on several levels. This made it possible to integrate recesses for additional stabilising supports in the manifold. The very space-saving arrangement of the valve gate drive units also helped to reduce the dimensions and weight of the center block.”, explained the former project manager at roth Benjamin Noack.
Despite the weight reduction, additional measures were required to stabilize the mold, which is operated by four rack drives, on the machine. For instance, the central block is guided in the reinforced machine bed and additionally supported by an adjustable crosshead.
To ensure the most convenient one-handed operation for the end customer, when removing the wipes from the box, the hinged lid is opened by a push mechanism. This highly user-friendly enhancement was discussed within the first functional tests and essentially contributes to the success of the article, which is not only used for wet wipes only. Furthermore, a reliable opening and closing over the entire life cycle of the box must be ensured. Thus, the thin-walled component must be manufactured with highest dimensional accuracy.
Initial filling tests to gate the part via one gating point only, by using a prototype tool which has been purchased locally by the end customer, showed unsatisfactory results in terms of filling behavior. So, it was decided to use two gating points. In order to determine the optimum injection point positions, roth and EWIKON carried out MoldFlow filling analyses as well as pressure loss and shear calculations for the hot runner and the part in close cooperation. This also contributes to a further optimization of the product design. The results were validated in a 1-cavity pilot mold. The article is gated over a gate diameter of 1,2 mm (0.05 in) with an injection time of 0.15 sec. The first gating point is positioned centrally on the surface of the lid, the second on the frame structure of the removal opening. In order to achieve the highest part stability, the valve pins are opened sequentially to move the weld line of the melt fronts to the desired area 5 mm (0.20 in) behind the film hinge.
Each parting line of the production mold consists out of twelve parts; arranged in four horizontal rows of three parts each. For each row, the valve pins for the first and second gating point are actuated as a group via a corresponding design of the supply channels. This requires 16 pneumatic control circuits which are activated by the pneumatic control system of the injection molding machine. The 48 installed valve gate hot runner nozzles vary in length by approximately 10 mm (0.04 in), depending on the position of the injection point. The pneumatic drive units are integrated in two middle plates in an extremely compact back-to-back arrangement. In addition, cooled gate bushes are used. This does not only optimize the cycle time, but also improves the gating point quality. In total the mold features 78 control zones and 58 cooling circuits. Finally, a cycle time of less than 10 sec was achieved.
Since its start-up in spring 2019, the production line has been producing with a capacity of 50 million units per year. As comparable in-mold labelling stack molds for the packaging sector were only been realized in 8+8-cavity versions so far, the mold solution it represents the most demanding and highly sophisticated mold technology solution of its kind in Europe. The compact design, the high productivity and the high degree of automation, which enables the parts to be produced under highly hygienic conditions without any human contact at any point in the production process, leave no doubt that the UK Packaging Award is well-deserved.
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