It’s a metal part, measuring 22mm in diameter and 100mm in length, with a complex internal geometry inspired by the kind of diagonal interlacing patterns found in braiding.
Multiple strands are intertwined to create a continuous geometry that enhances the mixing process of this heat exchanger by incorporating conformal cooling channels within the braided structure, improving thermal management.
The part has been designed this way to ensure efficient heat transfer and maintain low shear forces. Because of these capabilities, the heat exchanger design would be suitable for applications involving viscous and immiscible fluids. This could be, for example, the food industry or energy sector, where low shear blending and mixing of raw materials or ingredients needs to be held at a constant temperature.
Its braided pattern favours mixing and provides a vast amount of surface area for heat transfer. But a field-driven computational design approach, which has seen a charge assigned to each braid, has offered an even more effective mixing of fluid, while the intertwining of an additional fluidic domain has maximised contact and improved the efficiency of heat transfer too. These geometries, design consultancy service provider Metamorphic AM says, have been created with purpose.
That purpose is to address the challenge of poor integration between mixing and heat exchange in conventionally made in-line static mixers because of manufacturing constraints.
For Sylatech, a manufacturer serving aerospace, defence, transportation and general engineering industries, it has estimated it could manufacture 20 braided mixers per run, with up to 96 runs a day providing a daily output of somewhere between 1800-2000 units. And despite Metamorphic describing its braided mixer heat exchanger as its ‘definition of design for additive manufacturing,’ that’s not how Sylatech would approach the manufacture of this component.
Sylatech
Braided mixer on wax tree
Rather than additively manufacturing the end-use part, it is instead opting for a ‘3D printing-enabled’ plaster-based casting process. This approach, similar to block casting and investment casting, uses a plaster-based moulding material, with the plaster easily washing away post-casting to enable Sylatech to produce complex geometries more often associated with metal additive manufacturing. As an extreme example, the company says it can produce lattice structures with wall thicknesses of 0.4mm and wall localised sections of 0.1mm.
“Sylatech’s casting process has traditionally been seen as a ‘niche’ and may have remained a specialist casting process if not for the sudden advancement and proliferation of suitable printing materials and larger, cheaper printers,” Rupert Sexton, Business Development, Sylatech, told TCT. “This is a game changer for Sylatech and other plaster-based investment foundries in that we can now offer geometrically complex shapes way beyond the scope of traditional casting processes in high volume.”
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To do this, Sylatech either prints a wax and applies it to a wax tree, or prints the parts, tree and runner system as one shape, before submerging it in a specialist mould material ready for casting. In series production, Sylatech would likely opt for the latter.
For the 3D printing aspects of its lost wax casting method, Sylatech runs a 3D Systems ProJet MJP 2500 IC machine 24/7 for prototyping and low-volume production, and has also been working with Voxeljet and Photocentric with a view to scaling its AM-enabled casting process for mass production.
The company sees its plaster-based investment casting approach as complimentary to metal AM, suggesting he process may be able to help fast track applications from R&D to series production. Though Metamorphic is a design consultancy service specific to additive manufacturing technology, it too sees Sylatech’s casting method as a way for organisations to ‘meet the growing demand for customised, high-performance components in volume.’
“Integrating AM with a well-established process like block casting, which has already been qualified for applications in aerospace, automotive, marine, oil and gas, provides a more straightforward pathway for AM methods to support these industries,” said Manolis Papsatavrou, Computational Design Lead, Co-Founder and Director at Metamorphic AM. “Sylatech’s process aligns perfectly with Metamorphic’s mission to drive the adoption of additive manufacturing and bring AM-enabled innovations to market. It has the potential to lower the cost barrier for high-performance components, thereby making it feasible to commercialise innovations that leverage the design freedom of AM.”
According to Sylatech and Metamorphic, the cast equivalent of the braided mixer shows ‘remarkable similarities’ to the printed part that Metamorphic had produced. In an initial trial, there was no redesign of the original geometry, and the cast part not only exhibited good dimensional accuracy, but also boasted a smoother finish. As the two companies move forward, Metamorphic has said it will look to refine designs to ‘better align with the nuances’ of Sylatech’s plaster-based investment casting process to ensure ‘even greater fidelity to the original AM design.’ It means all systems are go as Sylatech pushes ahead with its casting method.
“With Voxeljet and/or Photocentric, it should be possible to produce small parts like the braided mixer at high volumes; possibly 100,000 per annum. Traditional wax-based investment casting will always have a place for simpler, more traditional parts, but for Sylatech, our focus is very much on an AM-biased future,” Sexton finished. “The challenge for Sylatech will be judging the point at which we invest in bigger printers at our factory.”
This article originally appeared inside TCT Europe Edition Vol. 32 Issue 4 and TCT North American Edition Vol. 10 Issue 4. Subscribe here to receive your FREE print copy of TCT Magazine, delivered to your door six times a year.
