Innovations | thin wall moulding
The goal for producers of thin wall parts is to make lighter products more quickly and without sacrifi cing performance. Peter Mapleston fi nds out how
Paring down the walls
Developers of machines, moulds and key equipment components continue to come up with new solutions and technologies designed to produce thin-wall packaging and technical parts more quickly and more cost-effec- tively—all without compromising on their performance. Processors that take heed may have to make some substantial investments at the outset, but some of the claimed payback times are surprisingly short. Several new developments were on show at the Fakuma exhibition in Germany last October, and more will be presented in March at the NPE in Orlando, Florida. At Fakuma, Arburg used a 130 tonne packaging
specifi cation hybrid Allrounder 520H unit to demon- strate high-speed production of thin-walled ‘SKET’ yoghurt tubs, developed by major dairy packaging producer Uniplast Knauer and mould maker H Müller- Fabrique de Moules. The polypropylene tubs feature a special geometry that makes it possible to get the wall thickness down to below 0.2 mm while retaining a relatively thick sealing edge measuring 0.7mm to ensure reliable sealing of the lid. The tubs were decorated with peel-off cardboard labels. The plastic component of the total weight was 4.7g, which is around a quarter less than conventional yoghurt tubs.
www.injectionworld.com The machine at Fakuma was running with a
single-cavity mould and a robotic IML system. The cycle time was 3.7 s, with a fi lling time of just 0.12 s. The modular injection mould is based on a multifunctional design with heated needle-type shut-off nozzles. These can be changed quickly, depending on whether the lid or the tub is being produced and whether injection is to be from the inside or outside. Grooves arranged in a spiral in the mould act as fl ow aids during injection, ensuring that the melt reaches the thick sealing edge before it freezes. Cardboard labels of different thicknesses are applied to the side walls and base of the tub to provide greater stability. The labels are easy to remove after use to assist recycling.
Electrics gain ground Thin-wall packaging production requires a very high power density from the injection moulding machine, which must be able to provide high forces and speeds within an extremely short time. Traditionally the realm of accumulator-supported hydraulic machines, the thin wall packaging world is changing and electric technol- ogy is gaining ground. Italian machinery maker BMB was among the fi rst to
January/February 2015 | INJECTION WORLD 35
Main image: Thin wall containers
produced on a 650-tonne Engel e-Speed hybrid
packaging machine
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