Technologies and applications - Closure manufacture - more economical production
Closure manufacture - production is more economical thanks to ongoing improvements
There is constant pressure to lower the production costs of mass-produced goods such as beverage closures. The beverage closure PCO 1881 is shown as an example of how, besides weight reduction, measures concerning the injection moulding machine can lead to more economically efficient manufacturing.
The closure design PCO 1881 was launched in 2008. Since then, numerous versions have come into use. What is impressive about this is that the weight of the closure has been continually reduced: originally 2.45 grams when launched, it is now 2.3 grams for carbonated soft drinks and up to 1.8 grams for still water. These savings are also necessary in view of growing capacity, as several thousand tons of raw materials can now be saved each year. So what contribution can machine manufacturers make to this development?
In order to meet growing capacity as far as the machines are concerned, technical advances in the performance data of the injection unit, clamping unit and main drive are required.
In terms of the injection unit, it is the plasticising performance in particular that must be taken into account. In order to do this, Netstal is furnishing the ELION and EVOS series with the tried-and-tested barrier screw and the new unit sizes 1000, 2000 and 2900. The combination of high-performance screws and high-torque screw drives makes it possible to dispense high shot weights from a Netstal machine in the shortest possible time and with excellent melt quality. The PE-HD types used as standard with an MFI (Melt Flow Index) of less than two can also easily be processed in the same way, such as the newly emerging bimodal and multimodal grades.
In addition, the injection piston sizes were revised in order to achieve the same injection performance with lower oil volumes. The reduced oil consumption has a direct impact on the drive size and therefore energy consumption. Thanks to the improved performance of the EVOS / ELION injection moulding units, the hybrid 2000M unit can now be used instead of the hydraulic 2150 unit.
Different measures have been employed with regard to the clamping unit and drive in order to achieve the objective of reduced energy consumption. Priority should be given first and foremost to the selection of the right drive technology. The ELION and EVOS series offer optimum combination options to reduce energy consumption. Taking a hydraulic EVOS clamping unit, for example, the optimised toggle lever geometry as well as the optimised clamping cylinders inside together with hydraulic high-performance valves make a large contribution to energy saving. Turning to the fully electric ELION, it is possible to save energy here through recuperation. Accumulating braking energy "“ produced from closing the clamping unit, for instance "“ is fed back into the system and powers a further electric axis. Energy recuperation is to a large extent only possible with the Netstal 5-point toggle lever, which can cope with the fastest mould movements without the need for spindle drives which are prone to wear and tear "“ since Netstalʼs spindle-free clamping unit demonstrates virtually no self-locking, practically all kinetic energy can be recovered during the braking phases. This technology has been in use since ELION was launched in 2004, long before this technology came into use in Formula 1. In view of the optimisations and improvements listed above, energy consumption in the Netstal range (based on the production of a PCO 1881 closure weighing 2.3g) can be compared as follows:
| Data in kWh | SynErgy | EVOS | ELION |
| Main Drive(s) | 78 | 56.3 | 25 |
| Screw Drive | 23.5 | 25 | 25 |
| Heaters: Machine and Mould | 24 | 27 | 27 |
| Total | 125.5 | 108.3 |
77 |
In doing this we see that, in comparison with the SynErgy range (100%) and observing identical process parameters, there is a saving of up to 13% with the EVOS range and up to 40% with the ELION range.
As a result of the continuing reduction of closure weight, output can be increased, leading to a doubtless improvement in economic efficiency. The turning point was clearly shown in 2009 and 2010 when output could be significantly increased due to a substantial reduction in cycle time. Competitive advantages arise for closure manufacturers, which are not insignificant for this highly cost-intensive application. Besides the higher output per m², lower electricity consumption is a core feature of economically efficient manufacturing.
Ultimately, the low overall costs incurred in the manufacture of a closure thanks to the measures mentioned, incl. further improvements in closure design as well as mould and automation performance, are beginning to show. The specialists from Netstalʼs Business Unit CAP are in the very early phases of evaluating customer requirements and needs and implementing these in complete, ready-to-use production lines.
Contact: cap@netstal.com
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