thin wall packaging | Innovation
to be placed in the preform precisely where it is required to achieve the required wall thickness in the final package. This allows considerable potential to cut part weight and material consumption. Clarke says, compared to the plug-assist techniques
A pilot CuBe production system is currently under construction for an unnamed packaging firm
tonne of thermoformed parts,” says Clarke. “We have a waste-free process. One tonne of plastic makes one tonne of packaging.” The early stages of development of the Ecoform
process were supported with an innovation development grant from the UK government’s Technology Strategy Board. This included a theoretical analysis of the likely energy savings achievable by converting a standard one-litre rectangular PP ice cream tub weighing 26g from conventional thermoforming to PET and the Ecoform process technology. The data, based on standard machine operating energy consumptions, showed that energy use would fall from 0.043 kWh per tub to just 0.013 kWh. GR8 has now secured second stage development
funding from an undisclosed European packaging producer and is constructing a pilot production system, which is being designed and built by UK-based automa- tion specialist ADRO Systems. Clarke describes this CuBe machine as a hybrid stretch blow moulding and thermoforming system capable of handling PP and PET. It uses a four head indexing unit and is designed to accept two or four rows of cavities. All support integra- tion of in-mould labelling. While energy saving is the most immediate benefit of
the system, Clarke says the use of an injection moulded preform combined with the stretch-blow forming technology provides additional benefits to the user. Firstly, the injection moulding process allows polymer
used in conventional deep-draw thermoforming, the stretch-blow forming process also achieves a more even distribution of material and more consistent biaxial orientation of the polymers. In particular, material distribution is improved in the corners of rectangular packs. Stretch-blow forming also results in less material remaining in the base of the part. This is, in part, due to the direct contact heating technology employed, which allows temperatures to be precisely profiled across the preform. According to GR8, the process will be fast. Preforms
for production of a typical ice cream tub could be moulded on a 6s cycle using GR8’S proprietary VDM (Variable Displacement Moulding) injection compres- sion process (estimated based on the company’s hybrid BMB development injection moulding machine). The CuBe stretch-blow forming machine is designed to dry cycle at 1.5s, which Clarke says means production cycle times will be similar or faster than current thermo- forming machinery. While the stretch-blow forming process is said to be
suitable for use with both PP and PET resins, the performance and energy savings are greatest with PET, which also gives potential users the benefit of enhanced package clarity. The benefits are greatest in the case of deeper draw parts. Clarke sees the patented technique appealing to
manufacturers of a wide range of thermoformed packaging for its improved economics. It could also compete with traditional one-step injection moulding by allowing production of parts with thinner walls and improved molecular orientation. The opportunity presented by the ability to replace PP with a biaxial- oriented PET could also deliver benefits in low tem- perature packaging applications for products such as ice cream. “Even the best PPs can break if dropped straight from the deep freeze,” says Clarke. “Stretch- blow formed PET containers are almost unbreakable.” For more information click here.
Energy comparison: Conventional thermoforming versus Ecoform (26g thermoformed rectangular PP ice cream tub v Ecoform PET)
Thermoformed PP (35% skeletal waste) Sheet extrusion per tub 0.022 kWh Forming per tub 0.021 kWh
Total energy consumption per tub 0.043 kWh Source: GR8 Engineering
42 INJECTION WORLD | October 2012 Ecoform PET (no waste)
Preform moulding (per tub) 0.010 kWh Stretch-blow forming (per tub) 0.0034 kWh Total energy consumption per tub 0.0134 kWh
www.injectionworld.com
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