PETpla.net Insider 09 / 2011

CAPPING / CLOSURES 44 PET planet insider Vol. 12 No. 09/11 www.petpla.net Improved injection moulding machine design helps to reduce energy consumption and improve efficiency in closure manufacturing Cutting closure production costs There is constant pressure to lower the production costs of mass-produced goods, such as beverage closures. Improved machine design, including energy-recovery sys- tems, work with lighter weight and developing design to reduce the costs of closure systems production. Developments of the PCO 1881 closure design, launched in 2008, have continually reduced its weight. At launch, it weighed 2.45 g; it is now 2.3g when used for CSD and up to 1.8g for still water. The weight reduc- tion has led to raw material savings of several thousand tons each year. Machine manufacturers can also con- tribute, through technical advances in the performance of the injection unit, clamping unit and main drive. Plasticising performance in the injection unit is a significant factor and Netstal is now furnishing its Elion and Evos series with the established barrier screw and new 1000, 2000 and 2900 unit sizes. The combina- tion of high-performance screws and high-torque screw drives enables Netstal machines to dispense high shot weights in a very short time and with good melt quality. The PE-HD types used as standard with an MFI (Melt Flow Index) of less than two can also be processed in the same way, as shown in newly-emerging bimodal and multimodal grades. Netstal has revised its injection piston sizes, in order to achieve the same injection performance with lower oil volumes; reduced oil consumption has a direct impact on drive size and, therefore, energy consumption. The revised performance of the Evos/Elion injec- tion moulding units allows the 2000M hybrid unit to be used, instead of the hydraulic 2150 unit. In the case of the clamping unit, the first step is selection of the right drive technology. In a hydraulic Evos clamping unit, for example, optimised internal clamping cylinders and toggle lever geometry, combined with high- performance hydraulic valves, help to save energy. The fully-electric Elion recovers accumulated braking energy – produced from closing the clamp- ing unit, for example – and uses it to power an additional electric axle. Netstal’s 5-point toggle lever can cope with the fastest mould movements without any need for spindle drives, which are prone to wear and tear. Net- stal’s spindle-free clamping unit has virtually no self-locking, so practically all braking-phase kinetic energy can be recovered. This technology has been in use since Elion was launched in 2004, years before the emergence of Formula 1’s KERS (kinetic energy recovery systems).