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ePaper created 2015-06-12, 11:29:04 | version 1.39.0
13 They cause very complex optimisation work and costs, and in the worst case a high reject rate. This applies equally to press lamination and other versions of vacuum lamination like the “In Mould Graining“ (IMG) technology. On the way to the final process, unforeseeable problems emerge repeatedly, leading to substantial delays, to discussions concerning their possible causes, their remedies, and finally to unscheduled and not negligible costs. The interdependencies are manifold, they are often not fully understood, the details differ from one project to the next, and last but not least reliable standards are non-existent. What does an optimum laminate graining look like? How many vacuum cavities are required in which positions? What is the impact of the adhesive type, the amount etc. etc. …? From the technical side, there is agreement that when the graining is deep which is ideal, the solution is to have many vacuum cavities and to avoid an unsuitable geometric design of the structural component. These parameters, however, have a negative effect on the budget, and an optimum compromise of technical feasibility and costs must be found. This requires detailed product know-how. Looking for new, creative solutions, Kiefel (manufacturer of laminators), Jowat (adhesive manufacturer) and Hardo (engineering company for adhesive application technology) got together to develop a better understanding of the ever-more detailed processes, and this was when VACFLOW was born. It is quite a stretch from the brilliant idea to the functioning innovation, but the method which is now patented has already surpassed the original expectations. On the way to the innovation VACFLOW, the function of the grain on the injection- moulded supports played a crucial role for the adhesive application: Ideally, trapped air is allowed to escape via V-shaped pathways in the surface leading to the next bore. The principle: the deeper the pathways, the better. And just this is the challenge, because the graining is prepared by etching the opposite pattern into the surface of the mould. This necessarily leads to higher consumption of materials for the injection moulded component, since the graining is additionally transferred to the surface of the final structural component, also impacting its stability. This makes one thing clear: the deeper the graining, the heavier and more expensive the component, and the grain etching process into the injection moulding tool also has to be taken into account, which is quite involved. The central idea of VACFLOW is to relocate the function of graining of the structural component into the adhesive layer. Hot melt adhesive can be applied easily onto a foil in form of a defined pattern using a roller coating system. The trapped air can be removed through the pathways between the individual adhesive dots and reach the nearest borehole by applying vacuum. All of this sounds very simple and plausible, but the technical realisation was not easy. As almost expected, during lamination, the hot melt adhesive is very liquid and spreads out to form a smooth film, eliminating the original dot pattern. The first step was to develop a method to accurately measure the above mentioned effect, to determine the ideal gravure, specify the adhesive characteristics, and last but not least to prove that this method will of course function in serial production. Trapped air during vacuum laminating means more optimisation and more expenses.