Steed Webzell reports on the evolution of additive manufacturing techniques as they become more valuable in the product development process

Anyone labouring under the misapprehension that additive manufacturing (AM) is still a conceptual technology should think again. For instance, according to the Wohlers Report 2011, AM is already a US$1.8 billion industry which is set to become $5 billion by 2020.

For the uninitiated, AM is the process of making 3D solid objects (metallic or plastic) from a digital model. It works by applying successive layers of material, typically in powder form, before fusing them together to create the final shape. Since its introduction, AM has become a vital tool in the automotive product development process, allowing engineers to discover pitfalls and assess market reaction early in the cycle. The huge advantage is that physical models of prototype parts can often be produced within hours. Compare this with conventional processes such as casting or moulding and the competitive gain is plain to see. AM with metals has particular resonance for the automotive industry. The ability to reduce both time and cost in production make this generative technology increasingly attractive to vehicle manufacturers. For instance, with a primary focus on aluminium alloys, which provide the basis for lightweight automobile construction, Daimler AG is now embracing AM for several applications.

The OEM has collaborated with the Fraunhofer Institute for Laser Technology (ILT) in Aachen and AM specialist Concept Laser to develop a new laser melting machine, the X line 1000R, with a build chamber size that surpasses anything seen previously. The machine was developed for the tool-less manufacturing of large functional components and technical prototypes, with material properties that are identical throughout the range. At the heart of the X line 1000R is a high-power laser in the kilowatt range which, according to Concept Laser, allows an increase in productivity of up to a factor of 10 compared with standard metal AM machines currently available on the market.

The new machine was configured specifically to cater to Daimler AG’s requirements with the aim of replacing the costly sand-casting and die-casting applications used in the early phases of development. In future, the process will offer the possibility of generating lightweight structures with a high level of rigidity. This will permit the production of weight-optimised geometries, with almost no design restrictions.

As an industrial partner, Daimler AG was looking to achieve a significant increase in build-up rates; an improvement in surface finish; reproducibility and reliability of the machine as a result of appropriate process monitoring; and the qualification of further aluminium series alloys.

The Fraunhofer ILT supplied its know-how for designing the laser beam source and the matching optical lens system, to ensure the desired build-up rates of different aluminium alloys. In addition, the process control for dealing with the different alloys alongside the machine construction was established and the mechanical properties of the components examined. The findings of further work done by the institute, with respect to temperature control in the build chamber to avoid any component warping, and in relation to the design of the powder application system, were also implemented within the design of the X line 1000R.

The right mix

Turning to polymer-based solutions, many such systems already appear embedded in automotive plant development studios around the world. According to Objet, high uptake in the automotive industry of its Connex series of 3D printers is “because they can replicate up to an industry-high 107 materials and are the only printers that can print multiple materials in a single print”.

One of the main advantages of a machine such as the Objet Connex 350 3D printer is the ability to program a mix of materials to meet particular specifications. Recently, this very capability enabled specialist seal manufacturer Gti Corporation to quickly create prototype seals that would closely simulate the part’s performance characteristics once fitted to the vehicle.

The development team at the Dunstable, UK-based company says it is now able to create a level of reality for a prototype that is almost unmatched across the industry. Indeed, for automotive door and window seals, the team is now able to modify a rubber component to attain a specific shore hardness (pu) value. It can also set the printer to meet the elongation requirement to achieve the particular break point of a plastic component as well as providing fit, function and appearance.

The Objet Connex 350, supplied to Gti by UK distributor OPS, is able to create a high level of simulated accuracy for a printed 3D model using simultaneously applied materials through a series of jet sprays to achieve a resolution within 16μm. This enables the production of fine surfaces and achieves exacting levels of detail.

Prior to the installation of the Objet machine, Gti used stereolithography techniques. Here it was able to develop a master which would then be vacuum-cast to produce the model. However, this could take anywhere from one to three weeks depending on design complexity.

Material gains

Material technology is without doubt instrumental in the progress of AM technology. After all, successfully creating the actual shape of a prototype is of limited use without it being produced from the correct material.

With this in mind, Stratasys says its Fortus 400mc and 900mc 3D systems can now build high performance thermoplastic parts in black using the newly developed ULTEM 9085. Among the early adopters is Minimizer, based in Blooming Prairie, Minnesota, USA, which is deploying the material in functional tests of its truck fender prototypes.

The latest challenge for Minimizer is to enter the growing market of truck owners using fuel-efficient, super-single tyres. On these vehicles, one wide tyre on each side takes the place of two narrow ones. This lighter-weight configuration allows drivers to haul more payload and reduces rolling resistance so trucks go further on less fuel, or so says Minimizer mechanical engineer Martin Larsen.

Making narrower fenders and the associated bracket assemblies means creating all-new tooling – a big investment. With this in mind, it’s crucial for Larsen to get the designs right before committing to tooling, so functional prototyping is essential. In Minimizer’s rugged testing environment, fused deposition modelling (FDM) from Stratasys takes centre stage.

Here Larsen can build functional prototypes in just hours or, for large parts, days. And now that Stratasys offers ULTEM in black, the parts are very much at home on the shop floor, masking grease and fingerprints and taking abuse with no painted finish to scuff and scratch.

Developing the market

Ongoing R&D is driving advancements in the AM arena. Aside from the main vendors of this technology, around the world there are many education and research establishments looking closely at this field. Among the most eye-catching is work being conducted at the Fraunhofer Institute for Manufacturing, Engineering and Automation in Stuttgart, where EOS Formiga P100 technology (polymer-based) is being used to develop bionic designs in SLS, studying nature to create technical solutions.

Fraunhofer previously teamed up with control and automation specialist Festo to create the award-winning ‘elephant trunk’ robotic arm (Bionic Handling Assistant) that is both rigid and flexible in 11 degrees of freedom. Weighing less than 2kg, the arm is an addition to industrial robots, the idea for which came from the study of crabs (the gripper is based on a fish fin). For those wondering what might be next? Well, a crawling robot based on the movement of spiders has already progressed to prototype stage. It seems AM technology knows no bounds.