BOTTLE MAKING 30 PETplanet Insider Vol. 24 No. 05/23 www.petpla.net Flexible production with faster neck changes on the stretch blow moulder Complex process made simple Beverage producers who process both aseptically filled beverages and juice and carbonated soft drinks need to use 38 mm bottle necks for the former and containers with 28mm openings for the latter. If the bottle neck is to be changed on a PET line, however, to date a comparatively large amount of effort was required to convert the stretch blow moulder in particular. Machine stops of up to four hours are not uncommon. With its new, simplified neck changeovers KHS has now shortened the time needed to convert the InnoPET Blomax stretch blow moulder – including the preform infeed. It is usual to try to only manufacture and fill bottles with an identical neck on one line. If a water bottler wants to produce a still and a carbonated product alternately, until now they had to decide whether to use the higher and heavier neck really only necessary for carbonated water for both products or not. The bottler would then save time but waste material and money in the filling of the still water. The alternative would be to live with the long intermittent downtimes caused by a neck changeover. Besides these considerations, marketing often plays a role in a decision like this, calling for a bottle adapted to suit the various products. Combined lines such as these that require neck changes are very often found in Japan. Complex and timeconsuming process In order to gain an idea of just how complex the exchange of parts for the above process is on the stretch blow moulder alone, it is worth taking a closer look at the individual steps involved. First, the preform infeed needs to be adjusted and what are known as the mandrel heads replaced. These are wedged into the preform necks to guide these safely through the heating module. The grippers that transport the preforms by their necks to the blow wheel are then exchanged on the star wheel. Finally, the moulds in the blow stations, the blow nozzles and often the stretch rods and further grippers downstream that feed the finished containers to the subsequent filler need to be changed over. Here, the number of parts that need replacing depends on the size of the machine. The mandrels and shields especially are of particular importance: the higher the machine output, the longer the heater, as the containers may move faster but always need the same amount of time to heat up. On an InnoPET Blomax 16 stretch blow moulder with a capacity of up to 48,000 bph, around 170 mandrel heads and shields have to be changed by hand, for instance. This means that this part of the neck change is particularly relevant when it comes to the amount of time needed – unlike the exchange of the just 20 grippers that is quick in comparison. needed for two operators to convert the KHS InnoPET Blomax16 stretch blow moulder, for instance, has now been cut by a good two thirds to approximately 86 minutes – including the preform infeed. As the PET bottles in a block like the KHS InnoPET BloFill are held and conveyed by their necks throughout the entire machine, not only the stretch blow moulder but also the filler has been developed further in order to shorten conversion Arne Andersen, stretch blow moulding Product Manager, KHS If both aseptically filled beverages and juice and carbonated soft drinks are to be produced, for example, different sizes of bottle neck are needed. (S urce: Frank Rein old) In order to considerably speed up the conversion process as a whole, KHS has not just simplified the individual work steps involved but also the concept governing the entire procedure. “We started out by analysing how the operators work,” says Arne Andersen, stretch blow moulding product manager. “On this basis we then considered how all tasks could be made easier and organised as perfectly as possible – paying particular attention to the ergonomics. Magazines were thus installed that stop the operator having to repeatedly abandon the machine to fetch and carry change parts, for example. We also replaced the grippers to reduce the number of screws that need to be loosened. At the same time, newly developed mandrel heads are now used that can be simply removed by pressing a release spring. This process used to be much more complex.” In this case, KHS consciously went for an approach that thought all of the specific processes through to the end based on actual customer requirements, Andersen emphasises. Thanks to the simple neck change, the time
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