Approaches to energy efficiency for injection moulding in the packaging industry

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The plastics processing sector is one of the most energy-intensive industries. Plastic packaging manufacture particularly stands out in this respect with its high-speed machines and high production quantities. As the demand for high-quality plastic packaging will continue to rise, processors are focusing their efforts on increasing resource and energy efficiency. If we take the injection moulding process as an example, it is clear how numerous parameters need to be fine-tuned to advance these efforts.

Humanity does not have problems with water, land or food supply as yet. Two thirds of the Earth's surface is covered with water but a great deal of energy is required to convert seawater into drinking water and transport it to arid regions. Thanks to irrigation, many barren areas can be made inhabitable so that sufficient land is available for use. The Earth also provides enough food, albeit unequally distributed, but there is not sufficient energy for transport and storage. What is lacking, then, is energy and, consequently, it is expensive because moderately increasing prices for resources are supposed to provide an incentive to improve resource efficiency. In recent years, machine and labour resources have become ever more expensive, although gains in efficiency have also made them disproportionately more affordable. A company that has invested wisely will thus always be left with a saving. This effect has increased productivity in German industry, meaning that a mere 20 percent of costs in the plastics industry are labour costs. It is not low material prices but low costs in series production that are a key success factor for plastic products. Consequently, it is desirable to combine and integrate more process steps.

Bergi-Plast, a specialist in mould making and plastics processing, has also analysed this approach at its headquarters in Bad Gottleuba-Berggiesshuebel near Dresden, Germany. As a supplier to the packaging and automotive industries, the company and its 130 employees produce a wide range of plastic closures. The product portfolio includes components such as flip-top caps, screw caps, measuring caps, tube closures and canister caps for cosmetics, household chemicals, the pharmaceutical and food industries, and bottle and canister manufacturers. Around half a billion such parts are produced every year. Components for braking and steering systems for commercial vehicles, parts for tank installations and electrical assembly groups for the automotive industry are also produced in Berggiesshuebel and at a second factory in Dohma.

The company boasts modern machinery, including injection moulding machines with a closing force of 25 to 210 tons. Some of the machines are fitted with handling systems to remove and further process plastic parts. The Toolmaking Department is designed for moulds weighing up to two tons. Bergi-Plast's successful company development is based on a philosophy of an integral service range to meet maximum quality standards, provide an optimum price-performance ratio and ensure a consistent strategic direction. The company applies a mature, integral TQM concept without making any compromises to ensure its maximum quality capability standard is met. This includes quality management that is tailored to clients' needs and requirements. Bergi-Plast also has state-of-the-art equipment and a well-equipped measuring room.

When it comes to resource and energy efficiency, Bergi-Plast also attaches great importance to building climate control which is optimized for production conditions. The company uses heat recovery in injection moulding production to exploit further energy efficiency potentials. “As an energy-intensive company, we are aware that we will only retain our competitive edge if we reduce energy consumption to a minimum,” explains Matthias Zetzsch, Caps and Closures Project Manager at Bergi-Plast. “That's why we have been taking decisive action in this respect for many years and consistently use inventive, successfully implemented savings concepts. In the injection moulding process in particular, there are still numerous adjustments which could help us to advance these endeavours.” Due to the many influencing factors and their complex interaction, it is important to examine as many process parameters as possible to determine how greatly they affect energy consumption.

Matthias Zetzsch, Caps and Closures Project Manager at Bergi-Plast

This was also the case at Bergi-Plast when the company scrutinized its Production Department to identify energy-savings potentials. Zetzsch's attention was drawn to Blue Flow heating technology during the Technology Days at Günther Hot Runner Technology in Frankenberg. Standardizing thick film technology has allowed Günther to develop more energy-efficient hot runner nozzles. Compared to conventional brass body heating elements, thick-film heating elements are much finer and have a smaller diameter. Moreover, heat conductors can be attached much more closely and, consequently, on a more individual basis for each temperature zone as they are only some 20 µm thick. This also means that temperature distribution can be controlled much more precisely throughout the entire nozzle. Blue Flow technology allows hot runners to feature a space-saving, more customized, more energy-efficient design, which also makes the injection moulding process more efficient overall. Another consequence is that smaller injection moulding machines adapted to the activity can be used without reducing production output. Overall production not only becomes more flexible but also much more energy-efficient. Needless to say, this is ideal for companies such as Bergi-Plast which produce for the packaging industry and are also committed to sustainability and energy efficiency.

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Bergi-Plast has been using Günther's nozzles for several years now. During a series of tests, Zetzsch wanted to find out the advantages that an energy-efficient hot runner design would bring. He wanted to compare the values for energy use in three identical 12-section moulds used to produce tube closures (flip-top soft and flip-top super soft). The aim was to process polypropylene (PP) with a shot weight of around eight grams during a cycle time of around twelve seconds. One of the hot runners used was provided by Günther Hot Runner Technology and featured nozzles from the energy-efficient Blue Flow product range. Blue Flow 4SHT80S nozzles were fitted. The other hot runners and nozzles were identical in their structure. A current clamp was used on the same injection moulding machine with a direct electric drive. The production cycle was 24 hours.

The results verified Günther's affirmation that its machine can achieve energy savings between 20 and 30 percent compared to other hot runner technology. Zetzsch adds: “The results showed that savings potential in energy use can also be found in the tool design. To be more precise, we managed to achieve a saving of 23.01 percent compared to hot runner technology by other manufacturers. This also affirms our decision to install Günther hot runner technology, which we have been using since 2010.” Marco Kwiatkowski, authorised representative and responsible for Günther's Thick Film Department, says: “Blue Flow nozzle technology also enables power distribution down to the millimeter, which makes heating much more homogeneous. This means power can be highly concentrated in the front nozzle section, for example. This also has a positive effect on process stability and moulded part precision. What's more, reducing processing temperatures also makes it possible to reduce cycle times.” Ten years, including real-life testing with pilot users, were invested in research and development work on the Blue Flow hot runner nozzle. Standardization of thick-film technology for hot runner nozzles has provided Günther with a totally unique selling point on the market.

Improved sustainability

Advanced Hot runner solutions increase flexibility and sustainability

When it comes to saving a significant amount of energy, it is obviously important to reduce the energy consumed for plastic product production and make use of conditioning parameters such as fully electric injection moulding machines which, according to the manufacturer's specifications, reduce energy requirements by up to 50 percent in comparison to hydraulic machines. But there is a need to examine all the components in the production process if the aim is to achieve the targets of a resource efficiency program such as Prog Ress as a way of preserving natural resources for future generations and avoid negative impacts on the environment or meet capacity limits and achieve competitive advantages with efficient technologies. This is where plastics processor and mould maker Bergi-Plast is setting an excellent example with the use of Günther's hot runner technology. Consistent improvement in resource efficiency is a kind of life insurance against resource shortages and rising prices and ensures competitive edge.

* Horst-Werner Bremmer is the Head of Technical Application Consulting and Sales at Günther.

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