Collaboration reveals bottle concealed close at hand

Friedrichshafen, Germany — Two partners in the NILS intelligent lightweight structures network had a live demonstration at Fakuma of a complete production system making an insulated bottle holder in particle foam with a living integrated hinge, two integrated injection molded polypropylene screw-threaded fixing inserts and an integrated exterior decor.

Although Hiddenhausen, Germany-based molder and mold maker Krallmann Holding und Verwaltungs GmbH normally exhibits at Fakuma fairs in Friedrichshafen with a conventional booth, it teamed up this year on a joint booth with its well-established expanded polypropylene particle foam producer partner, Ruch Novaplast GmbH + Co. KG of Oberkirch, Germany.

The partners are showing a further development of the PCIM particle foam composite injection molding process that started originally with model aircraft wheels shown at Fakuma 2012.

The process begins with an articulated arm robot from Kuka Roboter GmbH, which picks up doughnut shaped EPP rings and inserts them into a single-cavity injection mold weighing 390 kilograms, designed and produced by Krallmann, mounted on a 1,000 tonne clamping force 470S 1000-170 injection molding machine from Arburg GmbH + Co. KG of Lossburg, Germany. FPT Robotik GmbH & Co. KG in Amtzell, Germany developed the robot and gripper system for the production cell.

After molding the red PP threaded inserts, the robot transfers the compact PP and cored EPP ring, in an intermediate component type introduced in 2014 and called “K-Fix” by Krallmann, to the foaming station, where EPP foam is applied to integrate each of the rings into the EPP that forms the bottle holder by controlled partial melting of the outer extremity of the rings to form a strong hermetically sealed bond.

But that is not the whole story. Krallmann managing director Ingo Brexeler said the single-cavity mold sets the K-Fix rings well within the foaming station cycle time. In fact, the foam machine is by no means standard, “as it has been designed to work with a minimum amount of steam and the usual tempering process used in EPP foaming has been eliminated. Otherwise, we would not have got anywhere near the short cycle time needed to harmonize with the injection molding cycle,” Brexeler said.

The EPP foam enclosure is molded as one part with two hollows to take up a bottle when folded, and the living hinge required to fold the enclosure over the bottle is formed by local compression of the foam by a hot slider in the foam mold, itself developed and supplied by mold maker T. Michel Formenbau GmbH & Co. KG.

The exterior decoration is formed in the same EPP foam material with a laser textured surface on the mold. The high degree of surface reproduction on the plastic material is also due to use of a segmented Vario CS/WH water-based dynamic temperature control system provided by GWK Gesellschaft Wärme Kältetechnik GmbH in Meinerzhagen, Germany, Brexeler explained.

“What you end up with is a very resistant and resilient decor,” Brexeler said, “and an easily recyclable part in a single material, as it's all polypropylene.”

Erwin Bürkle of Wobbe-Bürkle Partner consultancy said: “This is the first time ever that a foaming process has been shown live at a Fakuma fair — and not only that in any case also in combination with injection molding.”

Bürkle, the former KraussMaffei development manager, heads the NILS network based in Hitzacker, Germany.