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(Näfels, August 31, 2017) Netstal will be manufacturing three-layer coffee capsules using a precision co-injection process at Fakuma 2017 (Friedrichshafen, October 17 to 21, Hall A7, Stand 7303). An all-electric, two-component ELION injection molding machine delivering 1,200 kN of clamping force will be used to carry out the process. The sandwich injection molding process enables IML-decorated plastic capsules and many other packaging products to be efficiently manufactured with a reliable barrier effect.
Aroma inside: Live manufacture of barrier coffee capsules
Using the example of coffee capsules and in cooperation with system partners, Netstal will be demonstrating the merits of the co-injection process within the scope of injection molding thin-walled aroma protection packaging. Unveiled for the very first time at Friedrichshafen, the application will see an all-electric ELION 1200 produce the capsules on a VNC-integrated Plasdan additional injection unit equipped with a 4-cavity Fostag test mold. The overall cycle time will be around 4.9 seconds. An automated Beck handling system automatically places Verstraete IML in-mold labels into the mold and removes the decorated capsules after the injection process. Finished parts are then stacked with the opening face downwards and an IMD Vista optical inspection system integrated within the removal robot checks the position and thickness of the EVOH barrier. Finally, the Nespresso-compatible capsules are stored in bulk in a container.
ELION 1200-250/120: Elevated injection dynamics and peak precision
The manufacturing of thin-walled parts requires a very high level of injection performance. Not only the maximum achievable injection speed is decisive in this respect, but also the dynamics. Moreover, absolute precision and repeatability is also needed to accurately form the multiple layers. "With its all-electric main injection unit and additional vertically-integrated (via VNC) Plasdan unit, within a small footprint the ELION 1200-250/120 provides ideal performance capabilities that enable successful implementation of the co-injection process," declared Marcel Christen, Applications and Packaging Product Manager at Netstal. As a result of the unique transmission principle with double toothed-rack gear and high-precision force measurement integrated into the injection axis, the ELION main injection unit delivers premium dynamics and outstanding precision combined with absolute repeatability. The result is a shot-to-shot consistency that is otherwise unheard of on the market. Designed to work at very high speed, the clamping unit on the ELION simultaneously enables short cycle times for every application. Owing to a consistent modular design and a large number of additional equipment options, the ELION can be optimally adapted to meet the needs of various application areas.
Co-injection: Three layers to provide efficient aroma protection
The most important aspect of a coffee capsule is to protect the contents against the influence of oxygen, light and moisture; for only then is the consumer able to fully enjoy the aroma. Aluminum offers extremely effective aroma protection, but requires so much power to manufacture that the industry turned its attention to the benefits of using plastic for the disposable product. The decisive factor then was how to preserve the aroma. "Netstal's solution deploys the precision co-injection process and superb barrier effect of ethylene vinyl alcohol copolymer (EVOH) and polyvinyl alcohol (PVOH)," explained Netstal application engineer Reto Gmür. Single-layer polypropylene (PP) and polylactic acid (PLA) solutions are very popular. Although these are simple and cost-effective to manufacture, PP and PLA have no appreciable barrier effect. As a consequence, secondary packaging such as portion bags or similar are additionally required. By contrast, the high-tech Netstal application exploits the advantages of multi-layer technology. In co-injection injection molding, the melt from two injection units is injected into the mold cavities via the same sprue. "The material arriving first forms the outer section of the molded part, which encapsulates the inner core created by the second component. In the case of our coffee capsules, one layer of barrier-forming EVOH is encompassed by two layers of PP, effectively creating an extremely thin sandwich with an overall wall thickness of just 0.4 mm," explained Gmür. While the EVOH (0.06 mm) protects the coffee, the PP layers (each 0.17 mm) protect the EVOH, as the sensitive material would otherwise absorb moisture and lose its barrier effectiveness due to gas exchange. The result is an aroma-tight capsule that can be used without any secondary packaging whatsoever.
Further application options for multi-layer injection molding
"Multi-layer technology is extremely versatile in terms of usage and is also suitable, for example, for blocking out light or in the use of recycled materials," explained Christen. In the first example the inner layer could be replaced with a black polymer, while in the second example the outer layer would be new material and the core layer would be made from recycled plastic. Marcel Christen consequently sees a bright future for the process: "Sandwich injection molding offers such unique opportunities that we can envisage many other application areas in addition to portioning coffee and tea; for example baby food, soft drink concentrates, medicines and many more packaging applications that require reliable barrier effectiveness."
Netstal at Fakuma (Friedrichshafen, October 17 to 21, Hall A7, Stand 7303)
» Download: Photo 1: IML-decorated coffee capsules are manufactured using the co-injection process, with the EVOH core providing excellent aroma protection
» Download: Photo 2: Optimum injection dynamics and peak precision: The all-electric ELION will be equipped with a vertical additional Plasdan injection unit for the Fakuma application