Although the history of SLM Solutions, headquartered in Lübeck, Germany, is relatively short, the company’s founders may never have imagined how far the technology they helped pioneer would advance in such a short time.

Early-stage development of selective laser melting (SLM) saw the first commercial machine delivered in 1998. It met the specifications of making ‘unbreakable’ metal parts and stood as a testament to the two pioneers Matthias Fockele and Dieter Schwarze, who together worked in conjunction with researchers from the Fraunhofer Institute of Laser Technology.

Since then, 3D metal printing has evolved into one of the greatest influences on metal part production in recent history. The SLM process sees parts built in a chamber layer by layer with metal powder injected in a controlled manner then melted by laser beam to form a strong, solid structure. The technology has fast evolved from single lasers passing over the powder melting it layer by layer, to multi-lasers with high wattage increasing build speed, product quality and reliability, while reducing costs.

In a recent interview, Dr Simon Merk-Schippers, Director – Business Development for Aviation and Aerospace at SLM Solutions, said: “Lightweight construction, functional integration and production costs are ongoing topics. In addition to the aerospace industry, space travel, especially the launch market is undergoing a strong change. There is more and more rivalry and therefore more intense competition. Of course, this also leads to price pressure. It is interesting to note that smaller companies are gaining a competitive advantage by flexibly using our SLM technology.”

Fockele and Schwarze may never have imagined the advantages SLM would offer todays engineers, as the technology has presented new opportunities for changes to design specifications, and the realisation of complex parts that were once welded together can now be made as a single unit.

Recently Berlin-based engineering start-up CellCore produced a single-piece thrust chamber and injector for a rocket propulsion engine in collaboration with SLM Solutions, reducing numerous parts into one. The internal structure manufactured using SLM Solutions technology could not have been made using conventional methods. A rocket engine sustains exceptional heat levels during propulsion, so complex filigree cooling channels were integrated into the internal structure during the build process, increasing the efficiency of a combustion process that generates extremely high temperatures.

Biomimetic engineering

The thrust chamber by CellCore is another step in the realisation of 3D metal printing capability, a huge step beyond the 19-parts-into-one aircraft fuel nozzle developed by GE just a few years ago. But how was CellCore able to print such internal complexity? CellCore simply looked to the biological designs found in nature.

A dog is an amazing chemical detector. They inspect our clothes, carry-on luggage and bags for contraband items when we arrive at airports; they traverse war-torn fields planted with deadly explosives, sniffing out danger. Man-made devices have not been able to take the place of the nose that nature designed for our canine buddies. Recently, researchers ‘mapped the sniff’: the channels and breathing processes of a dog’s nose, in a bid to simulate or mimic what nature created to improve detection devices made by man.

Sharks are famed for their speed, so when engineers from Airbus attempted to understand shark speed with the aim of transferring this knowledge to improve aircraft speed, they were surprised to find that shark skin was composed of millions of small tooth-like riblets. These well-formed riblets had been adapted to serve two purposes, one of those is as a bacteria-repellent device, and the other has the purpose of enhancing the sharks’ swimming speed. Mimicing the skin structure Airbus developed small ‘riblet’ patches and fitted them to jetliners in airline service over two years. The findings revealed nature’s ‘shark skin concept’ was a highly suitable aircraft covering long-range flights.

These examples mimic nature, so why not look to natural structures surrounding us rather than invent new ones? Unlike artificial intelligence (AI) nature has been testing, trialling and fine-tuning structures, making adaptations and finding ‘best’ solutions for eons. Given this availability, bionic experts, engineers and computer software developers can imitate or mimic such biological processes and structures to optimise metal forms with the ability to make 3D printed metal parts lighter, more rigid or more stable. Today we are witnessing the emergence of a significant field known as biomimetic engineering where designs from nature are successfully leveraged into today’s product development, making for highly functional and effective products.

While a relatively new field of design, but already filling research journals, biomimetics is finding its way into a number of fields benefitting from the timely development of selective laser melting technology, 3D metal printing. CellCore GbmH in collaboration with SLM Solutions AG has developed a complex, highly functional thrust chamber for a rocket propulsion engine in a single build.

Biomimetic engineering reaches the space industry

Bionic experts, engineers and software developers at CellCore have developed software that optimises technical structures based on the internal structure of bones. CellCore believes there is no limit to the application of bionic engineering principles to optimise products across a range of industries. Already they have developed parts for racing cars with exceptional success, winning the BASF’s “Best Use of Fibre Reinforced Plastics” design.

Having reviewed the manufacture of office chairs, tram cars and orthopaedic products, CellCore have now applied the geometric design principles of biomimetic engineering to a groundbreaking structure in the form of a rocket propulsion engine: a single-piece thrust chamber and injector. By using SLM, the engine was manufactured in nickel superalloy IN718 to satisfy the aerospace industry’s strict requirements for materials.

IN718 is a precipitation hardening in nickel-chromium alloy with exceptional tensile, fatigue, creep and breaking strength up to 7,000 degrees Celsius. This hard material is difficult to process using conventional methods, but melting nickel-chromium powder based in a geometrically proscribed design in an SLM280 laser machine, reduced the inherent difficulties and costs of conventional manufacturing, while resulting in a more complex structure never before achieved.

Recently, Rolls Royce has sought the help of SLM Solutions by implementing quad-lasers that use multi-laser optics together with a bio-directional recoating mechanism for the development of aerospace components. The SLM500 laser systems have four lasers and can achieve build rates of up to 171 cubic centimetres, suitable for high-volume processing. The company aims to implement its expertise and knowledge of building 3D metal aerospace components to a system that offers far more opportunities for product optimisation.

Biomimetics in the automotive industry

Car part manufacturers have been quick to take advantage of the opportunities on offer with SLM to create efficient and economically attractive products.

Hirschvogel Automotive Group, a producer of high-strength parts for the automotive industry with plants in three continents, has one arm of its business tasked with part development and the testing of innovative products and high-strength components optimised for series production. Fully exploiting the benefits of ‘bionic design’ Hirshvogel Tech Solutions leveraged methods and structures developed by nature to produce a car steering knuckle, the automotive part that attaches to the suspension and steering system.

Using Aluminium AlSi10Mg resulted in an overall weight reduction in the part; however, by utilising bionic engineering principles a significant weight saving of some 40% in the neck area was achieved – a saving not possible in a conventionally forged part. This came about as the team developed specific Computer Aided Technologies (CAx) allowing them to fully optimise the design.

Part variants, initially based on solutions from nature, were assessed before being selected to meet the appropriate calculations. The use of biomimetic engineering allowed the reduction of weight in targeted areas as against a constant in the overall weight. Built as a single unit in the chamber of an SLM500 system, final tests were carried out on tensile and notched bar specimens achieving the required forecast test values.

What the future holds

Predicting the future should be left to Nostradamus, however, what seems certain is a rapid uptake of 3D metal printing as industry sectors realise the potential opportunities and value of optimising design through geometries in bionic engineering. The change, or interruption to conventional manufacturing, becomes more evident day by day, as differing fields of part production realise the challenging and exciting technological potential of additive manufacturing.