TECHNOLOGY | CAPS AND CLOSURES
Right: Caps will no longer be easy to separate from bottles when the EU directive 2019/904 comes into operation in 2024
thread types. Impact on the end customer should also be kept as low as possible, for instance, comfort of use should not be reduced. Closures need to be compatible with existing filling equip- ment and should be connected to the container throughout the entire product life cycle until recycling. Materials for the tethered cap are not changed. Impact on existing production lines should be minimised and output should not be reduced. In addition, opening and closing of the cap 15 times without loss of function must be guaranteed. Finally, the connection between tethered cap and container must withstand at least 25 N tensile force for containers where the mouth is an integral part, such as PET bottles, and 12 N for all other containers, such as composite cartons or squeezable packages. Currently, two main production concepts exist to achieve the new requirements for the production of tethered caps. “With the slit concept, the cap is cut after injection,” says Puskaric. “This has the advantage that current tools can still be used but requires an additional work step in production and significantly restricts the design scope of the tethered caps. With the bridge concept, a band is injected along with the cap, which requires new tools. The advantage of this concept, however, is that no additional work step is required afterwards, greater freedom of design is possible for the caps and the injection moulded connection between the cap and the band can withstand higher loads.” He continues: “There are currently two dominat- ing variants in the design of tethered caps. The lasso design refers to caps that are connected to the bottle with a two-part band. The cap is con- nected to the upper band and the bottle to the lower band. This design is relatively easy to implement with existing tools, usually only the sliders need to be reworked. The hinge design, on the other hand, allows the permanent connection of cap and container by means of a hinge, which optionally also allows the cap to be fixed in a defined position. The use of existing tools is practically impossible.”
Right: The Engel
E-cap is a high performance, precision machine tailored for cap and closure production
36 INJECTION WORLD | April 2023
www.injectionworld.com
IMAGE: ENGEL
As a result, the tethered caps regulation will have an impact on production. Puskaric says that due to the high demand in the market, many manufacturers are expected to start with the lasso solution first as the hinge design requires high investments in both time and in financial terms due to the need for a new mould. In addition, the hinge design may require adjustments to the filling line and the feeding of the tethered caps, resulting in further costs. As a trend for the future, it is expected that in the course of the changeover to tethered caps, many producers will consider switching from 1810/1811 cap types to 26 mm caps. The advantage is a possible reduction in cycle time and material usage. For the injection moulding machine, tethered caps require higher injection speeds and increased injection pressure, as the required cavity internal pressure will tend to be higher. The reason for this is the changed filling behaviour with an increased number of filling points on the TE belt. The necessary clamping force, on the other hand, will not increase with a change to a 26 mm closure. Engel says that it has a number of solutions for plastic caps and closures. Fast cycle times and reliable injection moulding equipment are crucial for the profitable production of plastic caps. The company adds that its all-electric high-perfor- mance injection moulding machines E-cap and E-motion are fast, robust and designed for high, continuous loads. Dynamic servo-electric drives combined with a compact design make the E-cap
IMAGE: ENGEL
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