Shifting boundaries with Greiner Packaging

20% material reduction for yoghurt cups

Greiner Packaging, based in Kremsmünster in Austria, has been producing plastic packaging for over 60 years – with a passion for its field and a drive for continuous improvement. One key motivator for the company is sustainability. As packaging becomes lighter all the time and fewer raw materials are required, production processes are having to meet fresh challenges. Thanks to e?speed injection moulding machines from ENGEL, Greiner Packaging is reducing the wall thickness of its food containers while enhancing efficiency.

“Our customer’s specification was to reduce weight as well as carbon emissions while maintaining container stability and improving recyclability,” says Andreas Ecker, Application Engineer at Greiner Packaging, looking back on the recently concluded project. The client – Austrian dairy Ennstal Milch – already applies high standards of sustainability in its thin-wall monomaterial cups for Greek yoghurt produced from polypropylene using the IML process. Striving for still greater things, however, the manufacturer of dairy products turned to Greiner in Kremsmünster. Now the yoghurt cups are produced here using 20 percent less material than previously.

“We managed to reduce the container thickness by 0.1 millimetres to 0.3 millimetres on the sides and 0.35 millimetres on the base. In-mould labelling, or IML, supports the lightweight trend,” says Ecker. Despite being just under 50 micrometres itself, the label provides extra stability. Thorough product testing revealed no drawbacks in filling or logistics; nor were consumers disadvantaged. Even when filled, the new-design yoghurt cups can be safely stacked; when consuming with a spoon, they sit in the hand with no discernible difference. The cups are suitable for hot filling up to 85 degrees Celsius as well as cold filling. This is important for Greiner as Ennstal Milch and Greek yoghurt are not the only beneficiaries of the new thin-wall range; the new lightweight IML cups are produced in different forms for many other products.

“Injection moulding technology enables considerable variance of shape, with very low production tolerances,” says Engelbert Pranzl, Plant Manager in Kremsmünster. Sealing edge or base, round or square – every food producer has its own specific packaging design, and Greiner needs to adapt flexibly. The packaging specialist serves global markets from its base in Kremsmünster. The focus is on Europe, with other production sites serving local consumers in the USA and Asia.

How wall thicknesses could be reduced: Hydraulic benefits maximised

Adjustments to the production process have made it possible to reduce wall thicknesses in food containers. With this in mind, Greiner invested in a new e?speed 380 injection moulding machine from its long-standing engineering partner ENGEL. “We turn the hydraulic power of the hybrid machine to our advantage,” says Andreas Ecker. “We need extremely high dynamics in the injection stage, which pushed our electric injection units to the limit. For the yoghurt cups, we have a wall thickness/flow path ratio of 1 to 240, and we inject at 1,700 bar.”

With the high mechanical stresses in mind, ENGEL designed its e-speed injection moulding machines – which combine an electric clamping unit with a hybrid injection unit – specifically for high-speed thin-wall applications. To ensure the cleanliness demanded by the food industry, the toggle lever is encapsulated.

Expansion of the series over the past year has further enhanced the performance of all clamping force ranges. The hydraulic inline injection unit with electric plasticising drive now delivers even greater injection performance. It is designed for injection speeds of up to 1,200?mm per second. The machine base and mould mounting platens have also been tailored more closely to the requirements of thin-wall packaging and the use of multi-cavity moulds – both with and without IML. The main aim is to ensure precision of machine movements while achieving durability. In the case of in-mould labelling in particular, repeatability is critical.

How the production works: Energy efficiency also maximised

The yoghurt cups for Ennstal Milch are produced fully automatically in a six-cavity mould. For this purpose, the 3,800-kilonewton machine is equipped with high-speed automation courtesy of Dutch IML specialist Brink. The robot takes the IML wrap arounds from the magazine and places them in the mould. After injection moulding, it removes the decorated and ready-to-use cups, directs them to quality control and stacks them on a discharge belt. The stacked cups are then packed into boxes in another automated process. The quality check is visual and performed with a camera; among other things, the correct position of the label is checked to ensure the contents are properly protected and will not subsequently spill out. Greiner's clients insist on zero errors.

The injection moulding machine, automation and quality control are designed for flexibility, so as to ensure the shape of the container and the form of the label can be changed in a short conversion time. Another consistent priority across the spectrum of products and moulds was maximum energy efficiency.

To utilise energy as efficiently as possible even in high-speed operations, the e-speed 380 is fitted with an energy recovery system. This system absorbs braking energy from the moving mould mounting platen and returns the stored energy to the motor to accelerate the platen again. “For us, the energy efficiency of the machine was a key factor in our decision,” emphasises Engelbert Pranzl. “Even though we are continually enhancing the performance of our production systems, we are committed to cutting energy consumption year by year.” Greiner Packaging appointed a dedicated energy efficiency manager to closely monitor all energy efficiency projects on the spot, paying particular attention to production processes. Within the factory, ageing hydraulic injection moulding machines are gradually being replaced with hybrid and all-electric machines.?