Extrusion International 5-2017

22 Extrusion International 5/2017 AROUND THE EXTRUSION gard it is worth mentioning that the regrind fed back into the multi layer foil as filler material consists of the 7 layer foil and is therefore composed of the five different viscos- ity materials which this contains. It was our joint objec- tive to achieve stable mixing and flow properties for this 5 material mixture. An unstable material composition, whether due to fluctuating bulk density or a change in material proportions, leads to reductions in quality of the extrudate, in particular when seven layers have to harmo- nise with each other. As we wanted to install a control option for this, we provided for the addition of virgin PP material to the regrind. Therefore, the continual enrich- ment of the concentrations of the percentage of EVOH and of the adhesion promoter in the total foil, triggered by the return of the stamping grid, can be stabilised at 14 and 12 per cent respectively and consequently the melt flow index.” (Fig. 6) A further concept detail is worth mentioning: due to the shortest possible return of the regrind, it does not cool down completely. A large part of the heat energy con- tained therein can thus be used for faster melting in the extruder, which leads to an improvement in the energy balance in view of a material throughput on the “regrind extruder” of approx. 500 kg/hr. All other material percentages are added volumetrically as virgin material in constant quality. The throughput quantities for the barrier material and the adhesion pro- moter are a maximum of 60 kg/hr. The throughput of PP layers, which are additionally mixed with a white or brown colour master batch, is somewhat more, at ap- prox. 110 kg/hr (see Fig.1). Complete machine transparently operable via master production computer All machine components are activated and operated via the remote controlled electronic modules specifically de- veloped by motan for this purpose. These are GRAVInet for gravimetric dosing units and VOLUnet for volumetric dosing units. They are connected to a ControlNet of the central machine control via Ethernet or TCP/IP. This can be extended up to LINKnet, a comprehensive plant man- agement system (Fig.7). It is thus possible with Linknet 2.0 to collect and log the process sequences and application Fig. 5: Central mixing station to supply the “regrind extruder”. In this, four material components come together (regrind from the silo or from the BigBag, stabiliser for the adhesion promoter and new PP material) which are added from the gravimetric dosing units on the third level. Photo 2-5: Author Fig. 6: Factors of influence on the composition of the regrind fed back into the cycle. Greiner Packaging Fig. 7: All functions and setting data of the complex conveying and dosing machine are controlled by CONTROLnet, an integrated control concept for the operation, monitoring and management of all steps of raw material handling and connnected to the motan master computer system via LINKnet 2.0. Photo: Author Fig. 8: Helmut Reckziegel, Head of Business Unit Capsules at Greiner Packaging and Horst Bar, the responsible Project Manager at Luger GesmbH look back on 40 years of co-operation with motan. Photo: Author