Understanding 3D printing: What are the true benefits for design engineers?

Those who do 'get it' generally love it, but many are still asking if this is a superfluous exercise that is more about marketing gimmickry than true engineering advantage. However, a general ignorance of both the technology and where it can be used must take part of the blame for these attitudes. This has not been helped by the many names the technology is known by, which are often used fairly interchangeably by all but the experts. Rapid prototyping, stereo lithography, SLS, FDM, 3D printing, rapid manufacturing, metal sintering... the list goes on. "It does cause a lot of confusion," says Steven Wilcox, sales engineer at Objet Printer Solutions. "People ask what the differences are and though 3D printing certainly sits very well with people, additive manufacturing is the overall term and best describes the process; adding material as opposed to removing it." The technology has moved along since the days of the fragile models that were not to be touched. Many desktop machines now offer materials that can mimic numerous physical properties. These can be printed in a single go with many parts that can show form and fit, are able to move and can be used to check functionality. "People want to get more from additive manufacturing," says Wilcox. "Before, engineers might print a part, see it, pass it around, use it for marketing and then chuck it in the bin. But now they ask what analytical data can be found out? Do the parts from a CAD model fit together the way that's expected? Is it a snug fit? Is it a press fit? We want people to be able to test that functionality." Objet recently announced that its Connex range of 3D printers can create over 100 different materials ranging from rigid to rubber-like substances in terms of texture, standard to ABS-grade engineering plastic in terms of toughness, as well as from transparent to opaque. Many of these materials are derived by the mixing of more than 30 primary materials to enable designers and engineers to simulate precise properties that will closely resemble the intended end product with a high degree of realism. This ability to match proposed properties with those available from additive manufacturing has left some seeing opportunity and asking whether traditional production methods are needed at all? Ian Halliday, chief executive of 3TRPD, which offers plastic and metal additive manufacturing services throughout the UK and Europe, says: "As it has become more competent, it has progressed from being purely visual to being production capable, especially on the metal sintering side. However, for production, it is still too expensive for most people and sectors. "You can't compare it to injection moulding on price unless it is a very short run like in aerospace and motorsport. We are making parts for the inside of test jet engines, non-critical plastic parts for aircraft, and even some components that have gone in to space. Now it is a question of working down from those top end applications." Additive manufacturing allows exotic geometries to be made that might leave conventional plastic moulders or CNC machinists scratching their heads. This offers a unique proposition: a move away from design-for-manufacture towards design-for-function. In conjunction with Within Technologies, 3TRPD produced a heat exchanger to provoke thought and show just what the capabilities of the technology are. The device was produced using direct metal laser sintering (DMLS) and was made up of a number of teardrop-shaped tubes. Inside was a series of struts (Turbulators) created to increase internal surface area and disrupt the flow of the cooled fluid and maximising heat transfer. The outside form was designed to increase the cooling surface area and maximise the work done by the air passing through the device. "There is definitely scope for creating structures that you can't produce in any other way," says Halliday. "There are constraints, though, particularly with the metals, but also with plastics. The geometrical constraints might be minimal but you can end up with a poor surface finish or integrity. "Customers need a realistic sense of excitement so they don't go rushing off thinking it will solve all their problems, because it won't. Designers need to understand the constraints and then design around them. It is working from a different viewpoint, so you need an open mind, but the opportunities are plentiful." Additive manufacturing also allows flexibility in production and making 1 or 1000 makes little difference to unit price. Tweaks to geometries such as hearing aids or implants, can easily be made without affecting the downstream process. This is something on which Sheffield-based Materialise has tried to capitalise. "It gives you design flexibility," says Johnathan Andrews, UK account manager for additive manufacturing solutions at Materialise UK. "You can change the design without much investment. You can build 20 parts one night, decide you want to change the design and it won't cost you anything other than a couple of hours of CAD work. It therefore facilitates customisation and gives the potential for additional revenue streams. "It has allowed us to move in to the medical industry making bone structures. We are able to take CT scan data and create replacement parts for a patient whether it be a jawbone or, hip or knee replacement." The team was also able to facilitate the rapid design and production of Belgium's Group T University's Formula Student entry. The chassis of the Areion electric kart was made using Materialise's mammoth stereolithography machine which prints parts up to 2100 x 680 x 800mm, and the process allowed a number of unique design features to be incorporated. First was the textured surface that was printed directly onto the nose. The shark teeth-like ridges aim to improve aerodynamic performance. Additionally, the left side pod used complex channels that put nozzles behind the radiator to optimise cooling by directing the airflow directly through the radiator. In the right hand pod, the complex channels created a cyclone effect that removed water and dust from the air before it entered the engine compartment. The chassis was produced in just two weeks and the structure stood up to the all the knocks on track and heat from the engine. "This is an example of how additive manufacturing has made a design viable," says Andrews. "The key driver was to be able to manufacture it quickly and have the ability to easily change the design. It was also more cost effective than any traditional manufacturing route they would have gone down." In most cases, however, additive manufacturing is not about replacing existing methods, but rather complementing other technologies within a business. It is not just individuals, but also companies that need to take a look at their products and recognise the opportunities for additive manufacturing. "We believe designers and engineers can create better products if they have additive manufacturing in their toolbox," says Andrews.