thin wall moulding | Technology
Above: Sumitomo (SHI) Demag will offer a fast cycle version of its new IntElect all-electric machine for thin wall applications
Thin wall moulding is a key area Sumitomo (SHI) Demag is focusing on with its new IntElect all-electric machine range. Previewed at the K fair last year and rolling out during 2017, it will be offered in standard and fast cycle versions. The standard version is aimed at technical moulding applications formerly run on hydraulic machines; the fast cycle version is pitched at sub-7s cycle time applications requiring improved speeds, precision and dynamics. Fast cycle variants, for example, offer injection speeds of 300-350 mm/s. At 50 tonne version was demonstrated at K2016
Right: IML containers
produced on a Netstal Elion machine and Plastisud injection
compression mould on a 4.9s cycle
producing lightweight dosing closures. The 7.6g 38mm diameter closures were produced on a 13s cycle and featured wall-thicknesses ranging from 0.8-1.2mm and included a complex membrane. To ensure complete and reliable filling, the machine used both the company’s activeLock and activeFlow- Balance functions. “The key development for thin walled/fast
cycling applications is the ability to optimise the machine movements specifically for the application and without the need for an expert,” Flowers says. “The PID control parameters are brought out onto the screen in a simplified format – allowing the user to define and control acceleration and deceleration ramps. This allows the machine axis to be optimised to the mould,
which results in maximum performance.“ The improved dynamics of all-electric machines is also being exploited to support multi-cavity injection compression moulding, which was also demonstrated by Sumitomo (SHI) Demag at K using an El-Exis SP420 machine running a 2+2 cavity stack mould from French mouldmaker Plastisud. In the injection compression process, the melt is injected into the still partly-open mould and the final closing stroke is used to distribute polymer to complete the fill. The result is a reduced fill pressure, allowing thinner parts to be produced with lower residual stresses and warpage than could be possible with conventional injection. Injection compression moulding technology was also
demonstrated at K2016 by KraussMaffei group company Netstal, which combined it with IML decoration on a 280 tonne Elion machine running a 4+4 stack Plastisud mould with Machines Pagès automation. The system was producing 425g yellow fat tubs weighing 10.7g on a 4.9s cycle.
The injection-compression process is different from
conventional injection moulding due to the resulting material shrinkage while the melt is cooling in the cavity, also referred to as the ‘shrinking effect’,” says Netstal spokesperson Michael Birchler. “In conventional injection moulding, this is carried out during the hold pressure phase by ‘pressing in’
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