Moving beyond prototypes

A father and son backyard project will soon see the creation of a life-size, functional Lamborghini Aventador. The car is not entirely 3D-printed but demonstrates the potential of additive manufacturing (AM) for the wider vehicle industry. Kostas Poulios, principal design and development engineer at Pailton Engineering, explains how he used 3D printing in large vehicle manufacturing and whether it could play a role in the production of safety critical parts.

Outside of novelty projects, 3D printing is already an important part of vehicle production. From tooling, parts manufacture, design, and prototyping components, the industry is widely considered a pioneer of integrating 3D printing into design and manufacturing support processes. However, automakers are not producing safety critical vehicle parts with AM.

Steering system

Steering systems are put through intense conditions throughout their lifespan, particularly when used in large vehicles such as military, utility, and commercial trucks. Each part of the system, including the drag link assemblies, steering and suspension ball joints, and bevel boxes must be able to withstand heavy shock loads.

Due to high shock loads, components for steering systems cannot be manufactured with some of the common materials used for 3D printing – at least, not to a useable standard. For instance, Acrylonitrile butadiene styrene (ABS), a thermoplastic filament that is regularly used for fused deposition modelling (FDM), does not provide adequate properties for the manufacture of steering system parts.

Although strong and lightweight, the material is not powerful or durable enough to be used in a steering application. Instead, ABS modelled parts are suitable only for rapid prototyping.

An alternative material would be metal matrix composites (MMCs), composites with at least two constituent materials. Hybrid composites that combine three or more materials provide more strength, as several elements can be combined to improve material properties and ensure the part meets requirements.

For niche steering systems, such as those used in commercial trucks, construction, and military vehicles, MMCs can provide designers with an opportunity to expertly engineer the metal that is used to make their part, while also reaping the advantages of 3D printing. This includes the potential to topologically optimize parts to maximize strength-to-weight ratio. This is particularly advantageous when used in combination with other design tools, such as finite element analysis (FEA).

To manufacture MMC safety critical parts requires selective laser sintering (SLS), a technology that prints components from metal powder. Currently, this method can be costly and time consuming. Looking into the future, when SLS 3D printers become widely available and more cost effective to use, this may change.

As in every optimized steering system, any work outside the conventional manufacturing processes will be more expensive. An exception to this rule would be low production volumes. However, these cases are usually undertaken with the intention of larger volume production in the future.

When considering whether to implement 3D printing into parts production, manufacturers must understand that the advantages might not outweigh the initial cost. This is certainly the current case for 3D printing for safety critical parts. However, the method is valuable in other areas of production.

AM is successfully used in the design phase of safety critical components. For example, Pailton Engineering uses an HP DesignJet to create prototype steering system components from ABS, including ball pins, drop arms, steering wheels, suspension joints, and forgings. In these cases, the 3D-printed part is not used for production but is replaced with a production equivalent once the design is finalized.

At Pailton Engineering, using AM during design provides the design and production engineers with a visual representation of steering parts and assemblies. This helps identify issues and improvements before production begins to provide customers with the correct first-time solution, every time.

Pailton Engineering Ltd. http://pailton.com