FEATURE ADDITIVE MANUFACTURING/ 3D PRINTING The porosity problem Having evolved, in a short space of time, from a revolutionary
technology into a mainstream process, additive manufacturing is enabling the fast and cost-effective production of complex high-quality components in a range of materials. But for all its state-of-the-art advantages, it can also be subject to a
more traditional and well-recognised manufacturing problem: porosity. In a quest to resolve this challenge, additive manufacturer Graphite AM turned to Ultraseal International
A
dditive manufacturing has seen a significant growth in applications in
recent years. A clean and simple process, it produces high-quality components on demand, all without the need for expensive tooling or machining. 3D printing enabled the quick
development of prototypes, while small and intricate parts could be cost- effectively produced as one-offs or in low volumes. As a result, the process was adopted by cutting edge and hi-tech industries including motorsport and aerospace. As the technology became more familiar, however, its benefits became more widely recognised. Today, it is becoming an increasingly viable manufacturing option across all sectors, and a new breed of companies has emerged to meet the demand. One such company is Graphite Additive
Manufacturing, a 3D printing consultancy specialising in complex designs and high-performance components in tailored materials. The company’s original customer base was almost exclusively hi-tech sectors including automotive, motorsport, aerospace and defence. While the company still serves these sectors, it has seen a real growth in other industries. Jonathan Warbrick, sales & marketing
manager of Graphite AM, commented: “Additive Manufacturing is no longer a revolutionary process for prototyping and limited production runs. The cost and turnaround mean it’s of huge benefit for low-mid volumes – typically 250-500 component runs and tooling. Manufacturers have seen this and are turning to 3D printing for the fast and reliable supply of high quality parts. It’s an area of huge potential, and has become a strategic focus of our work.” Working to a 3D model, Graphite AM
primarily uses SLS (selective laser sintering), an additive manufacturing process which deploys lasers to sinter powdered material, binding it together to create a solid structure. While the majority of 3D Printing Bureaus use standard or
26 NOVEMBER 2018 | DESIGN SOLUTIONS
Glass filled Nylon materials, Graphite AM has developed its own range of unique SLS blends, including the use of fine graphite particles. As well as having impressive anti-static properties, the use of graphite also improves impact and thermal resistance (up to 170˚C), meaning it is particularly suited to lightweight applications where strength and performance are critical factors. Combined with the ability to produce
complex shapes and highly detailed designs without the need for metal tooling dies, Graphite AM is now supporting a wide range of industries. These include components for automotive applications, turbo system components, plenum chambers, oil and water pipework and manifolds, fuel cells and EV battery cooling systems. It also produces components for mission critical applications including environmental monitoring systems and unmanned aerial vehicles (UAVs).
POROSITY PROBLEMS Porosity has long been recognised as a major issue with die-cast components. During additive manufacturing, microscopic holes are formed within the body of a part. Though invisible to the eye, these reduce the overall density of the component, potentially leading to cracks, leaks and fatigue. In applications with pressure differentials or which need to be air or fluid tight – for example in cooling systems – this can
be an especially critical issue. In 3D printing, this porosity is typically
caused either by the printing process itself, or by the powder used in the process. To help minimise this issue, Graphite AM began the search for a specialist porosity sealing partner, and chose Ultraseal International. Dr. Mark Cross, commercial sales
director at Ultraseal, said: “Ultraseal has unrivalled experience and understanding of the component impregnation process and a proven track record of developing the highest quality solutions to the problem of porosity in die-casting and electronic component manufacture. Though the technology is different, the challenge is similar, and we’ve been able to use our knowledge to create an effective solution. It’s pleasing to see that our technology will continue to have a key role to play in sealing components manufactured from new materials and processes such as additive manufacturing.”
THE SOLUTION Ultraseal’s solution involves sealing the component using vacuum impregnation, a process which uses three key stages. First, components are placed into an
autoclave containing Ultraseal PC504/66 resin, a high performance thermocure methacrylate sealant. This is applied to the component under vacuum in the autoclave. Once components are immersed in sealant the vacuum is released, allowing the sealant to penetrate into the micro-porosities and leak paths within the 3D printed part through the resultant change in pressure, which draws the sealant into any micro-porosities and leak paths. Second, a cold wash module removes
excess sealant from external component surfaces and tapped holes. The third process stage is a hot cure cycle. This exposes components to heat for a predetermined time period using a hot water bath which polymerizes the sealant, changing it from a liquid state to solid polymer by applying heat. As a further quality test, the components are pressure tested to ensure they are leak free. Approached initially as a consultant
and solutions provider, Ultraseal now delivers an end-to-end sealing service for Graphite AM. Warbrick commented: “Our customers
Combined with the ability to produce complex shapes and highly detailed designs without the need for metal tooling dies, Graphite AM is now supporting a wide range of industries
rely on quality components, and we rely on Ultraseal to ensure they’re sealed effectively against the problems of porosity. Our partnership means we’re able to deliver reliable and leak free components, an essential characteristic in high performance parts.”
Ultraseal
www.ultraseal.com / DESIGNSOLUTIONS
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