In today’s electric as well as internal combustion-powered cars, engine mounts are the single most important component in reducing the transmission of vibrations from the powerplant aggregate to the vehicle structure and therefore the passenger compartment. This makes the engine mount a crucial element in maximizing passenger comfort through minimizing NVH – Noise, Vibration, and Harshness.
For almost a decade, engine mounts have mostly been made of injection-molded, fiber-reinforced polymers rather than metal, as this material is lighter and has superior acoustic and vibration damping characteristics. Today, the imperative of ever-shorter automotive component development cycles is putting this class of materials and traditional design processes under heavy pressure. Simulating, prototyping and proving the NVH performance of critical parts needs to be carried out more quickly and cost-effectively than ever before.
Daimler AG chose to partner with Forward AM when 3D printing technology for prototyping was still in the very early stages. Forward AM was therefore the natural partner in Daimler’s continual drive to optimize the NVH performance of its automotive engine mounts.
Forward AM has repeatedly proven that with Additive Manufacturing materials and technology, fully functional prototypes can be produced much more rapidly and at far lower cost than with traditional injection molding. The digital modeling and simulation software suite applied by Forward AM’s Virtual Engineers greatly accelerates design optimization loops, maximizes design freedom, and eliminates the very costly requirement for new molds with every design modification. A further compelling advantage is that the customer’s machine-tool acquisition and maintenance expenditure is cut radically.
Daimler and Forward AM’s joint goal was to radically accelerate the engine mount development process and at the same time achieve major cost savings. The new process needed to fulfil all the requirements for full validation through digital simulation, and the Additive Manufacturing material selected had to display comparable NVH performance to traditional injection molded parts when fitted to the latest Daimler aggregates.
To leverage the advantages of Additive Manufacturing for the new generation of Daimler engine mounts, two core criteria had to be fulfilled:
When these criteria were applied to the initial design of the new prototype, it quickly became clear that the polyamide-based compounds generally used in this 3D printing application field – PA11 and PA12 – would not fulfil them. A more rigid and thermally stable material was called for.
The perfect match for the challenge was Forward AM’s Ultrasint® PA6 MF, a mineral-filled polyamide 6 that outperforms PA11 and PA12 in every key mechanical and thermal stability aspect in this specific application. Furthermore, it ensures rapid and precise 3D printing with today’s Powder Bed Fusion (PBF) technology.
Alongside the advantages of Ultrasint® PA6 MF in fulfilling Daimler’s two core criteria, this advanced material from Forward AM delivers a further convincing argument: While the filling in most powder-based AM materials is provided as a dry blend, in Ultrasint® PA6 MF it is integrated as in-particle filling: This ensures a more homogenous distribution of the filling and therefore optimizes the material’s consistency in processing. Compared to dry-blend AM polymers, in-particle filling enables more constant mechanical properties of the printed part, as it eliminates the risk of incorrect remixing after material separation.
Ultrasint® PA6 MF applied through Powder Bed Fusion can produce test-ready prototypes in under 48 hours – the same development process with injection molding generally takes several weeks. This pairing of AM material and 3D printing technology was selected for the cost and time-efficient development of the engine mount prototype.
The Virtual Engineering team of Forward AM applied BASF’s suite of digital tools to find a geometry which makes the 3D printed part behave like the injection molded pendant. The engineering challenge was to re-design the 3D printed part, such that the acoustic behavior (modal frequencies, NVH) matches the injection molded part without violating the available design space. This was achieved by performing a topology optimization with a specifically formulated objective function. The geometry which was found shows a totally different internal reinforcement structure compared to the injection molded part. The internal design is enabled by the 3D printing process and not feasible with injection molding, due to its demolding and wall thickness restrictions. Although the 3D printed part looks different – regarding the internal load paths, it can be used like the original part as a fully functional prototype in the development stage when no injection molding part is available.
To confirm the NVH, mechanical and thermal properties of the engine mount produced with AM material and technology, Daimler engineers carried out comprehensive tests on the prototype and validated its NVH performance profile through model analyses of the component at differing temperatures, as well as in direct comparison with the original injection-molded part and also a geometrically identical 3D printed part.
Exhaustive testing confirmed the new component prototype fulfilled Daimler’s strict requirements in all NVH-relevant performance aspects: This confirmed the outstanding suitability of Ultrasint® PA6 MF as an Additive Manufacturing material for NVH-optimized engine mount prototypes with their geometry reengineered through digital simulation.
Throughout the entire test, the geometrically optimized engine mount 3D printed with Forward AM’s Ultrasint® PA6 MF showed no mechanically or thermally induced structural alterations whatsoever, providing further confirmation of the tremendous potential of this AM material for the new component prototype.
With the combination of Forward AM’s advanced Ultrasint® PA6 MF and BASF’s suite of digital tools, Daimler engineers successfully leveraged the full potential of Additive Manufacturing for the digital simulation, prototyping, and benchtesting of their NVH optimized component. From this leading global manufacturer’s perspective, the result is a compelling advantage in terms of component prototype development speed and cost-efficiency.
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