Dr Otto Urbanek, author of the EUROMAP Study “Energy Efficiency: European Plastics and Rubber Machines Well Placed”, sees close links between energy efficiency and productivity. Investing for greater productivity generally also means investing in energy efficiency. The study looked at the main plastics and rubber processing technologies, i.e. injection moulding, extrusion, blow moulding and thermoforming, which account for around 90 per cent of the total volume processed.
The production efficiency of injection moulding machines has more or less doubled in the last 20 years. Machines are now capable of a manufacturing output that would once have required twice as many machines of similar size. Developments in manufacturing technology have provided a significant performance boost. The demands made on hydraulic systems have resulted in greater efficiency and cut the energy consumption of injection moulding machines by around 40 per cent.
The throughput capacity of extrusion machines has also doubled over the same period. Machine-related energy consumption has been reduced by around 20 per cent. The same is true in compounding: twice the amount of material is being processed with machine-related energy consumption down by 20 per cent at the same time.
Increasing use has been made of servo drives in cyclic processes such as injection moulding, blow moulding and vacuum forming technologies for a number of years now. These allow the energy required for motion to be cut by half. Plants with a conventional, central power source and system-related line and control losses are increasingly being replaced. Servo engineering has long since made the breakthrough in such high-performance areas as packaging and medical engineering. Servo systems now also offer simple solutions for energy recuperation. In injection moulding, for example, during rapid motion of the closing units, the drives are used as generators to produce energy when braking. The same principle is also used with fast-working closing units of blow moulding machines and in thermoforming machines.
Looking to the future, there is no doubt that the use of energy-saving and highly dynamic components will provide a significant boost in terms of improving energy efficiency further in the next ten years. Greater use of all-electric drives and servo-hydraulic designs instead of conventional technology will pave the way for further efficiency gains – in some cases as much as 50 per cent.
The most important part in improving machinery is played by developments in process engineering: advances in screw technology have brought a significant increase in throughput rates while at the same time improving the quality of the melt. This has allowed extruders and the injection units of injection moulding machines to become smaller and better while maintaining performance. Radiant heater systems show great potential in thermoforming machines.
There is also a great deal of potential for combining several processes: this is of particular interest if residual heat from one stage in a process can be used in the following stage with a view to eliminating reheating altogether.
In conclusion: if increasing productivity continues to drive European plastics converters’ investment decisions in the future, energy efficiency will benefit.
Major savings can also be achieved if converters fine-tune processes to minimise energy consumption. Monitoring the flow of energy in machines, installations and in the plant also produces results. It makes the energy requirement transparent, which in turn contributes to tailoring energy consumption to need. This will ultimately reduce operating costs, incidentally helping them meet the European Commission’s target of cutting energy consumption by 20 per cent by the year 2020.
