KHS enables faster, simpler neck changes on its stretch blow molder

Whereas in the past only one category of product was usually run on aseptic lines, bottlers of sensitive beverages now face an ever-growing demand for flexibility. Beverage producers who process both aseptically filled beverages and juice and carbonated soft drinks need to use 38-millimeter bottle necks for the former and containers with 28-millimeter 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 molder in particular. Machines were often stopped for up to four hours, tying up the often very few operators of the same for a disproportionately long period of time.

With its new, simplified neck changeovers, KHS has now shortened the time needed to convert the InnoPET Blomax stretch blow molder – including the preform infeed.

In order to gain an idea of just how complex the exchange of parts for the above process is on the stretch blow molder 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 that 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.

KHS allows flexible production with faster neck changes on its stretch blow molder.

Finally, the molds 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 molder with a capacity of up to 48,000 bottles per hour, 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.

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 analyzing how the operators work,” introduced Arne Andersen, stretch blow molding product manager. “On this basis we then considered how all tasks could be made easier and organized 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 emphasized. “We aimed to achieve the best possible improvement within the shortest possible time.”

KHS managed both: thanks to the simple neck change, the time needed for two operators to convert the KHS InnoPET Blomax16 stretch blow molder, for instance, has now been cut by a good two thirds to approximately just 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 molder but also the filler has been developed further in order to shorten conversion times.

The capper was one particular area of focus, where the cone responsible for lifting and closing the bottles needs to be replaced manually. No conversion is required regarding the screw cap, however, as there are two cap feeds – one for each neck diameter in the respective format.

Andersen is convinced that the new neck change option will give beverage producers much greater flexibility, as they can now also run much shorter production cycles for bottles with different necks and therefore reduce their warehousing effort accordingly.