TECHNOLOGY | FOAM MOULDING
before injecting the gas, KraussMaffei said. The updated design modularity of the three-zone section allows for processing of a range of materi- als. The company says a one-thread, three-zone section could be designed for example with a two-thread three-zone section, which would be better for process- ing a 30% glass-filled PA6, the company says. It designs single- flight and double-flight three zone areas using a modular system. KraussMaffei also optimised the design of the
non-return valve used in the modular screw design. Through analysis by the developers, the most effective design of the middle non-return valve (M-RSP) – which closes at the end of the metering process and separates the mixing and gas supply area from the three-zone section, preventing melt from flowing back – is one with a ball check valve. “This is the only way to keep the critical pressure above 33.9 bar and thus prevent foaming in the plasticising unit,” the company says. The design of the M-RSP also ensures a constant shot weight.
Below: KraussMaffei’s PX 321-1400 machine produced a foamed storage table for trucks at Fakuma
Fakuma demonstration The KraussMaffei team investigated the previously existing and newly developed screw using PP with flow indices of MFI 11 and MFI 44 and containing mineral filling or a glass fiber content of 20% or 30%. It also evaluated the screws by processing ABS and a 30% glass-fibre filled PA6. The plasticis- ing performance changed depending on the compound selected and the parameters set, such as dynamic pressure. KraussMaffei says its in-depth research yielded additional benefits, making it possible to develop
Above: KraussMaffei says its HPS Physical Foaming screw (fitted on a PX 321-1400 machine using the MuCell process) delivers 30% higher plasticising performance compared to current screw technologies
screws specially adapted to a material. This option is appealing to customers who manufacture what KraussMaffei call corresponding products constant- ly over a long period of time. One example is for quick tests. At the Fakuma 2023 exhibition, KraussMaffei installed the HPS Physical Foaming MuCell screw on its all-electric PX 321-1400 injection moulding machine in the production of a foamed storage table application for trucks and commercial vehicles with partial in-mould label decoration. The company says the demonstration application repre- sents an area of products (visible intricate parts) that have not yet been the focus of physical foaming technology. The application represented the first use of its APCplus machine function with a gas-charged melt. APCplus is a process optimisation software option created to keep the production process constant by analyzing and dynamically regulating the injection moulding process when parameters deviate due to external factors. It shifts the change- over point and holding pressure profile from shot to shot based on the measured melt viscosity to deliver weight constant components. The demonstration application required
KraussMaffei to partner with several companies. Wirth Wekzeubau of Helmbrechts, Germany, supplied the mould that is designed to help achieve the maximum possible degree of foaming. Special mould cooling channels are designed into the mould to prevent a post-blow effect, which creates bubbles that can emerge on the surface of the part. The cooling channels ensure uniform cool- ing at the cavity surface without the use of variot- hermal techniques. Reichle of Bissingen/Teck,
32 INJECTION WORLD | November/December 2023
www.injectionworld.com
IMAGE: KRAUSSMAFFEI
IMAGE: KRAUSSMAFFEI
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