Photo by Coveris 500g Eurotub made by Coveris using injection compression moulding.
Injection compression moulding (ICM) using stack moulds can produce thin wall packaging which is up to 20% lighter in weight than current packs, according to the technology’s developers.
The adaptation of ICM for stack moulds involves technology patented by French mould maker Plastisud, and this was demonstrated by Netstal on its stand at Fakuma in October. Since then rigid packaging producer Coveris has revealed it has been running the technology since the start of 2015, saying it is the first industrial ICM and stack mould system incorporating in-mould labelling (IML).
“The development of the new injection compression technology started in 2011 as a joint development project between Coveris, Unilever and Plastisud,” said Coveris.
The system was installed at Coveris’ Centre of Excellence for IM-IML in Ravensburg, Germany. The ICM system has a 4+4 stack mould and is producing 500g Eurotubs for spreads.
The Ravensburg facility also processes materials from Coveris divisions in other countries, including 40μm in-mould labels from Coveris' EU Food & Consumer Business Unit in Angoulème, France. “By doing so, Coveris can offer its clients a real one-stop solution: a lightweight packaging with high quality decoration up to the rim,” said Coveris.
Yves Caunègre, group development manager at Coveris Global Rigid, said: “Our injection compression IML is a great achievement in the improvement of the established injection moulding IML technology. I am confident that it will become a great success story for all parties involved in this technology development for thin wall packaging.”
Nathalie Fabbro, head of marketing at Plastisud, told Plastics News Europe that Plastisud has no exclusivity agreement with any company regarding its patented technology and it is looking at many commercial opportunities in the rigid packaging market.
“We are targeting high consumption markets where the need for stack moulds is important; the USA, for example,” she said.
Plastisud uses Netstal injection moulding machines at its headquarters in Castelnaudary, France. It worked closely with Netstal to optimise the Swiss company’s machines for ICM with stack moulds.
At Fakuma in October, Netstal demonstrated the process on an Elion 2800-2000 machine using a 4+4 cavity mould, making a margarine tub from PP that weighs only 10.7 g. The tub was developed specifically for the Fakuma demonstration.
The project required close collaboration between Netstal, the French mould maker Plastisud and the automation specialist Machines Pagès, based in France.
The ICM process involves partially filling the mould cavities at a speed of 100 milliseconds, before the mould is fully closed. The process is performed at a low pressure which reduces stress in the material. Netstal says the high quality of the platen parallelism guarantees a synchronicity of 99.98% between the mould, machine and automation system.
“It’s not rocket science, the technology is already established. But it’s not been done before with stack moulds,” said Markus Dal Pian, vice president, sales and marketing at Netstal, during the Fakuma press conference held by its parent KraussMaffei Group.
He said there are various benefits of the ICM process compared with injection moulding. It reduces the clamping force needed, so the 280-tonne Netstal machine is about half the size of machines already in the market for such packaging applications.
The mould is filled a lot faster too. Overall cycle time of 5 seconds is not class-leading, but Dal Pian called it “quite respectable.”
But where the ICM process really comes into its own is the better quality product and the material savings that can be gained.
The use of ICM can achieve 20% part weight reduction compared to an injection moulded part with the same mechanical properties. In the example of the margarine tub, ICM saves 2.3 g of polypropylene, which corresponds to savings of €124,000 in material costs per year, said Dal Pian.
The high precision of the system is the result of two years of development work by Netstal, Plastisud and automation specialist Machines Pagès, based in France, in which they mastered the challenges of combining the ICM process with the technology of a stack mould.
The acceleration of the screw to 800 mm per second takes only 40 milliseconds. This is equivalent to 48 g, or roughly 20 times the acceleration of the Earth, or five times more than the maximum acceleration of the Saturn V booster rocket.
Dal Pian highlighted the importance of near-100% accuracy in synchronising movements during the cycle. The compression position of the clamping unit can be completely reproduced. The clamping unit position precisely determines the start of the injection process. And the position of the screw precisely determines the start of the internal mould compression stroke. A deviation of just 1 millisecond would result in a shot weight difference of plus or minus 1.1 g.
“Getting this co-ordinated with everything in the process leads to this amazing performance in terms of part geometry,” he said.
In a Netstal release, Thomas Iten, packaging application engineer at Netstal, said the benefits of ICM for packaging companies include narrow wall thicknesses and a lighter product resulting in lower unit costs. Also, the end product (particularly lids) shows fewer signs of distortion and has greater dimensional accuracy, because of lower stresses placed on the material.
“The unique injection compression moulding technology guarantees perfectly balanced parting planes, with an extremely low dispersion rate,” said Plastisud CEO Laurent Buzzo.
The automation input from Machines Pagès included IML adapted to the machine and mould.
At the Netstal stand, Plastics News Europe was told by a company representative that there has been a lot of interest in the ICM stack mould system from packaging companies. The development partners are now studying a version of the system with an 8+8 cavity stack mould.
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