Lightweight Summit 2019
Lightweight Design in Production: Processes and Tools
At this year's Lightweight Summit, Mario Braun from Kamax Automotive, Jochen Rühl from Reichenbacher Hamuel and Joachim Gundlach from Grunewald demonstrated how weight and costs can be reduced by using different processes and materials.
At the lightweight summit on March 26 and 27 in Würzburg, Mario Braun, Vice President Product Management at Kamax Automotive, gave a brief overview of ultra-high-strength fasteners in the chassis area. He spoke about the so-called "KXtreme" screw, which is comparable to a conventional screw in terms of hydrogen insensitivity but is 22 percent lighter with the same clamping force. According to Braun, this results in lightweight design and cost saving potentials by downsizing or reducing the number of screw positions. In order to determine suitable components, Kamax carried out a screening together with the engineering service provider EDAG.
One of these components to be optimized was the wheel carrier: The engineers have completely redesigned the wheel carrier using 3D simulation and saved around 400 grams. In addition, the diameter of the screws was reduced; instead of four, only three screws are now required. Elementary advantages are a simplified assembly, an improved power flow in the wheel carrier due to the triangular shape of the screw points and a reduced screw weight of about 59 grams.
The optimization of the surrounding components resulted in savings on the connecting element as well as further solutions for easier construction. In cooperation with EDAG, the Kamax engineers optimized the topology of the installation space of each surrounding component and then validated it using FE simulation. According to Braun, this has enabled the companies to increase the strength and reduce the weight of some fasteners. The weight reduction of the screws totaled 275 grams. All in all, the engineers have reduced the weight of the complete assembly by around 675 grams, and the unsprung mass on the front axle by around 1,350 grams. According to Braun, some OEMs are already using this wheel carrier.
"Not a Mechanical Engineer, But a Systems Specialist."
Jochen Rühl from Reichenbacher Hamuel was the second speaker to explain the importance of lightweight design as an enabler. For Rühl, "lightweight design doesn't need to be reinvented to evolve". He therefore welcomes the fact that OEMs are investing heavily in electromobility despite the austerity measures they have taken. After all, lightweight design is essential, especially in the field of electromobility: Battery boxes made of aluminum not only secure the battery modules, but also cool them and protect the battery from water. Another particularly important aspect is the protection of the battery in the event of a traffic accident. Precision in manufacturing is a prerequisite for the material to take its effect.
Reichenbacher Hamuel, for example, uses straight milling cutters or those with right- or left-hand twist for the production of aluminum extrusions. The nozzle body is firmly locked, equipped with a targeted air jet and requires no water, but can be provided with a lubricating component if required. The adequate selection of the spindle and the drives is also decisive for the precise production of the workpieces.
This is also true for machine rigidity: According to Rühl, various criteria such as the desired machine dynamics, the size of the machine, the precision or milling speed as well as the material are decisive. In Rühl’s eyes, Reichenbacher Hamuel is "not a machine builder in the true sense of the word, but a system specialist who masters the entire process chain".
Different Low-Pressure Sand-Casting Processes
Joachim Gundlach from Grunewald was the last speaker at Session Production I and spoke about thin-walled aluminum structural castings for body and chassis parts. He presented two different printing processes and their process chains: Low-pressure sand casting and additive mold production. Both processes are equally suitable for the production of thin-walled structural castings for car bodies, chassis and in semiconductor production.
According to Gundlach, the company can produce low-pressure sand-casting models in around twelve weeks before the initial sample is manufactured. "This is relatively fast compared to series production, although it can also be used to produce small series of up to 1,000 units per year," says Gundlach. Grunewald mainly uses this process to produce prototypes and pilot series. Apart from the technical know-how of the designer, the most important factors in the manufacture of the components are the component position, the gates, the splitting technology and the cooling technology. These parameters are determined by numerical casting simulation.
According to Gundlach, this preparatory work is crucial before the final raw part design of a component starts. Once the component position has been determined, the pitch is determined and the 3D model is milled, then radii and transitions are manually adjusted, and the models assembled. Casting is carried out in the low-pressure casting process from bottom to top. Joachim Gundlach explains that an important advantage is that the mold filling and the printing time curve can be controlled very easily.
Freedom of Design of Casting and Mold
Using additive manufacturing, the component is ready after just 4 to 6 weeks, because model making is no longer necessary. Essential advantages of this process are the free design of casting and mold. According to Gundlach, undercuts and hollow structures can also be realized, giving the foundryman a certain degree of freedom, and consequently allow new geometries and products. Grunewald uses an "ExOne" machine and phenolic resin (PepSet) in its production. “PepSet" is a 3-component system consisting of a binder, a hardener and a liquid catalyst. Curing takes place without the formation of by-products such as water or formaldehyde.
The chemical material offers a good flowability of the sand during mold production and enables a high dimensional stability with clean radii and corners without sand residues. The process can be used to produce relatively large components such as tailgates and longitudinal members. However, the tolerance is not as precise as with die casting.
This article was first published by Automobil Industrie.
Original by Jens Scheiner / Translation by Alexander Stark
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