Adapter plate: 80 % lighter due to clever steel replacement
Is it possible to replace a mechanically highly stressed structural component made of solid steel with a plastic solution? The answer is yes – as shown by a project that BARLOG Plastics realized together with the company Viebahn Systemtechnik. The newly designed and produced plastic solution consists of only three instead of nearly two dozen parts and weighs only 4 instead of 19.5 kilograms – with massively reduced manufacturing costs and simultaneous fulfillment of all mechanical requirements.
Transport racks play an important role in global corporate logistics: They are used, for example, to transport heavy engines over long distances between OEM plants. For handling reasons, these are usually attached on one side via a so-called adapter plate to a suitable transport rack, with the dimensions of a Euro pallet. This adapter plate must therefore absorb and withstand considerable weight forces, torques and strong dynamic accelerations, for example during transport over uneven roads. For this reason, they are usually made of steel. “As is usual in steel processing, their manufacture is made from several machined parts and is therefore very complex,” explains Erik Schoppmann, operations manager at Viebahn Systemtechnik GmbH, Wiehl, a renowned supplier of high-performance load carriers for the automotive industry. “In addition, in times of climate change, the high weight of such steel structures is also increasingly being critically questioned. That’s why, as one of the industry’s technology leaders, we took an interest in lighter alternatives made of plastic at an early stage. After all, we’ve already been checking every one of our manufacturing steps for its environmental relevance for years.”
Schoppmann was able to win BARLOG Plastics GmbH as a partner for this ambitious project. There, the challenge was first approached with a detailed feasibility analysis, in which the existing steel geometry was chosen as the starting point. As a material, the engineers of the Berg-based supplier of high-end solutions for the entire plastics industry chose Grivory GVL-6H HP, a polyamide with partially aromatic components and 60% long glass fiber reinforcement. “Grivory is a proven metal replacement material that we have already used several times with great success,” explains BARLOG Plastics expert Tobias Wiebel. This is proof of the decades of experience that the Overath-based company has gained not only in plastics product development, materials analysis and rapid prototyping, but also in competent material selection: BARLOG Plastics has compounds for practically all applications in the plastics processing industry – including material solutions for special cases where, for example, thermally conductive or electrically conductive materials suitable for injection molding are required.
On board from the start – optimal for complex projects
“Grivory GVL-6H HP is pretty much the maximum of what we have in our quiver in terms of stiffness and strength – even when you include the economics of the application in the focus,” Wiebel says. For the initial analyses, it was assumed that the adapter plate would be dynamically stressed by four times the engine weight of around 250 kilograms. Even the initial calculations were positive for the BARLOG Plastics project team, which was coordinated by Daniel Könemann in addition to Tobias Wiebel. Of course, the challenge was considerable. But, says Wiebel: “Based on the feasibility study, we quickly gained the impression that we could solve the task well by means of design suitable for plastics” – in line with the BARLOG Plastics motto: ‘From the idea to series production’. “The sooner we can bring our expertise to bear, the better.”
In this case, BARLOG Plastics was even on board from the very beginning – optimal conditions for such a challenging project. Together with Viebahn Systemtechnik, a design space was defined and built as a 3D model. The topology and geometry of the new plastic adapter plate were then optimized in several simulation steps. The result was a virtual structural component from which the main load paths could already be derived.
Top technical performance economically and environmentally friendly
Subsequently, the geometry was further adapted in further iteration steps to suit the plastic and the tool; FEM structure simulations were also used here, with the help of which the BARLOG Plastics team was able to analyze any mechanical weak points in advance by simulation and optimize them, for example, using suitable rib structures and wall thickness adjustments. “Steel components are produced by machining from the solid by removing material from where it is not needed at great expense in terms of time and labor. With plastic components, it’s the other way around: injection molding is a primary molding process in which material is specifically introduced during production only where it is needed – and only there,” Könemann explains. “It’s a completely different approach that requires a completely different level of expertise. So in principle, we built the adapter plate from scratch after the topology optimization.”
In parallel, work began on detailed injection molding simulations, among other things to determine the best gating points. “Here, for example, we focused on the optimal alignment of the load-bearing fibers and placed weld lines in areas of the component that are subject to as little stress as possible,” Wiebel said. “There are only a few suppliers on the market who have mastered all of these methods that we used here, i.e. injection molding know-how including simulations, design and FEM analyses in one package.”
In addition, the decision was made early on to further optimize the force application by using two steel inserts – these also had to be fitted in line with the process in order to interlock all three components of the plastic carrier in the best possible way while still in the injection mold. At the end of the process, there was a plastic adapter plate that not only convinced as a digital model, but also proved itself in practice: “We not only carried out the usual load tests,” emphasizes Viebahn plant manager Schoppmann, “but also subjected the component to further extreme loads in order to put it through its paces. Our result is clear: the plastic version is on a par with the metal version.” “This is exactly what we were aiming for,” adds BARLOG Plastics employee Könemann. “For us, it’s important that the product works in the end and doesn’t just meet the abstract requirements of the specifications.”
At just four kilograms in weight, the Grivory adapter plate is around 80% lighter than the original steel one. Thanks to injection molding, some expensive manual assembly or manufacturing steps are also eliminated – compared to the steel variant, manufacturing costs are reduced by around 50%. “And the environment benefits too,” says Schoppmann. After all, with 52 girders per truck transport, a weight saving of 15.5 kg corresponds to around 800 kg less load. Even for a trip from Hamburg to Munich, this represents a CO2 saving of around 25 kilograms. “Of course, this fits in perfectly with our ambition to become European sustainability champion in our industry,” says the Viehbahn operations manager.