MACHINERY | THIN WALL MOULDING
The focus of the high-performance application
was a CAP-Line with a clamping force of 4500kN. With the line, Netstal now offers injection moulding machines pre-configured for closures. The exhibi- tion machine is based on the Elios platform and is pre-configured for efficient production of beverage closures.
An all-electric clamping unit with a dry cycle
Right: Netstal demonstrated moulding of a 15g thin-wall cup made from 100% PET
time of 1.4 seconds enables fast cycle times of less than 2 seconds. An optimised barrier screw allows a smaller injection unit to be used. The new design ensures a higher plasticising perfor- mance and a better degree of homogenisation.
Weight issue In its collaboration with Netstal at NPE, StackTeck said its mould technology delivered a high level of thin-walling by combining its Thin Recess Injection Molding (Trim) with seven sequen- tially controlled valve gates. “We set out to establish a new standard in moulding PET containers using at least 30% content of hard-to-fill PET with a high IV level mixed with a high volume, easier-filling low IV PET resin with the intention that customers would be able to run the same part using 30% rPET,” said Vincent Travaglini, CEO of StackTeck. Some of its customers on the PET preform side of the business are running 100% rPET for beverage applications, and this points the way towards adding PCR capability for thin-wall containers, he said. The hot runner used for this mould incorporates
Yudo’s ISO technology to enable tightly spaced valve gated drops on the bottom of the container, while incorporating independent control of valve gate timing to suit optimal filling of the part. The hot runner is custom designed for high pressure injection, with thermal profiled nozzles and a balanced thermal management approach. The IML automation system was also supplied
by StackTeck, including side entry robotics, as well as a downstream vision inspection system and downstream stacking. Separate to this, StackTeck says its Trim technol- ogy has helped customers to save around 1.65 million lbs of material per year. In a recent example, a life cycle assessment
(LCA) was performed on a rectangular thin-wall food packaging container. The LCA assessed the environmental impact resulting from lightweight- ing a 1-litre container using Trim technology for a
26 INJECTION WORLD | January/February 2025
single production stack mould. Jeff Ngai, director of engineering at StackTeck, said: “In this study, a 21% weight reduction – from 28g to 22g – resulted in a 19.5% reduction in the carbon footprint of the whole process, from resin extraction to end-of-life of the product.”
Electric performance Also at NPE, Arburg showed an electric Allrounder 720 A Ultimate – using injection compression moulding to produce thin-walled cups with an in-mould label (IML). The directly driven
machine, with a clamping force of 2,900 kN, is equipped with a size 1300 injection unit that is opti- mised for high performance. Thanks to high-precision servo
motors from sister company AMKmotion, high injection volume flows and injection speeds of up to 400mm per second can be achieved. The exhibit used a four-cavity mould from Brink
to produce thin-walled IML round cups from polypropylene (PP). For process monitoring, the mould was equipped with six inductive position measuring and embossing sensors. Four moulded parts, each weighing 10.8g and with a wall thickness of 0.37mm, in a cycle time of 3.95 seconds. The production cell also included a side-entry robot from Brink that inserts the labels, removes the finished cups and stacks them on a conveyor belt. In this packaging industry application, special emphasis was placed on energy efficiency and on a part design that saves materials. The use of injection compression moulding on an electric machine helped to improve energy footprint by 20% and reduce part weight from 13.0 to 10.8 grams. The flowpath-to-wall-thickness ratio is 380:1.
Usually, this would need a very high injection pressure – at the expense of energy requirements and mould wear. Injection compression moulding was used for this, because it requires a much lower injection pressure and can work with mould temperatures of 20C rather than 12C. The special ‘Next Cycle IML’ label can be
separated from the PP of the cup during recycling, so the product can be easily recycled after use. In contrast to thermoforming, no pre-produced foils are used and no stamping waste is produced, says the company.
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IMAGE: NETSTAL
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