For industrial sectors, one of the most definitive benefits of additive manufacturing is the ability to reduce weight whilst maintaining mechanical performance. The advantages here are crucial and can result in lower material costs, significant reductions in production time and for industries such as aerospace and automotive, increased design flexibility.
Left: Example of a Schoen Gyroid structure, Centre: Finite Element Analysis, Right: Lattice within brake calliper.
In order to achieve this, lattice structures must be added to parts before manufacturing. However, adding lattice structures to parts using traditional CAD techniques for AM can be difficult. It can be a particular challenge to produce the appropriate algorithms to generate triangulated surfaces for export to AM processes. For example, traditional CAD-based lattice techniques can obstruct the design fluidity that advanced manufacturing technologies allow, particularly when trying to reproduce complex ideal micro-architectures.
UK-based 3D image visualisation, analysis and model generation software and solutions provider Simpleware has a different approach to generating lattices for additive manufacturing. Implementing a process that coverts a CAD object into an image, known as voxelisation, the company uses an image-based method which allows designers to generate implicitly defined periodic lattice structures suitable for additive manufacturing applications and finite element analysis (FEA).
Simpleware’s patented method for generating robust lattice structures can overcome the problems faced with hollowing out a part to reduce weight and optimise designs prior to 3D printing. Cellular lattice structures can be used to replace the volume of CAD and image-based parts, reducing weight whilst maintaining optimal performance.
Lattices can be integrated with CAD parts within Simpleware software to create hollow watertight models that maintain exterior geometries to a specified wall thickness. The image-based approach makes it possible to manipulate the lattice and the final mechanical properties of a part before it is exported as an STL.
“Our image-based method has many benefits, as by allowing the user to work in image-space as well as CAD, many operations can be performed robustly without the risk of compromising the original geometry of a part,” Dr David Raymont, software developer at Simpleware, explained. “The method helps overcome some common challenges in creating lattices from CAD in terms of easily changing features such as part wall thickness and volume fractions to achieve custom properties.”
Racing Ahead
A recent case study which set out to reduce the weight of a racing bike with Direct Metal Laser Sintering showed how additive technology can significantly reduce the weight of a part by designing for a specific process. Modifying the design of the bike’s rear wheel brake calliper hanger, Simpleware’s internal lattice structure approach was employed to generate a structural lattice inside the hollow void of the part, allowing the part to be built without support structures.
Rear wheel brake calliper hanger made with DMLS.
Support structures are typically required to build unsupported geometric features on metal DMLS parts, but these supports can comprise up to 50% of the build mass and affect the unique design freedom that AM offers. Using Simpleware’s lattice structures in this case led to a 51% volume reduction over the original machined component. FEA was then performed to compare the performance of the component, manufactured in titanium, with the initial aluminium design. This proved that, though 18% lighter, the new titanium part demonstrated the exact same strength and stiffness as the original.
Innovation Through Collaboration
Simpleware has offered its hand to several projects over the last few years which have shown how lattices can inspire new designs freedoms for metal additive manufacturing. One of those is the ongoing LIGHT project, which is supported by funding body Innovate UK, to accelerate and implement CAD/CAM solutions for lightweight product development.
As part of the project’s seven-strong UK consortium, the company’s self-supporting low-density lattice structures are being used to explore the potential of metal additive manufacturing, particularly in the aerospace and automotive sectors.
David commented: “Our involvement in different industry projects on light-weighting has shown there to be a high demand for flexible and robust lattice techniques in the aerospace and automotive industries, particularly for increasing design options for parts. The hybrid techniques we use also mean that parts manufacturers can maintain accuracy to an original geometry while still robustly introducing lightweight lattice structures.”
Earlier this year, Simpleware joined UK-based AM specialist 3T RPD in the Innovate UK-supported GOSSAM project (Generation of Optimal Support Structure in Additive Manufacturing). The mission was set up in 2013 to develop innovative and advanced intelligent metal additive manufacturing support structures.
Through this unique partnership, software solutions are being developed to automate the orientation of parts for AM and then generate support structures for them. Simpleware has offered its expertise to the project to further the automatic generation of support structures in a bid to reduce costs and time and ultimately streamline the process across the 3D design to manufacturing ecosystem.
Image-based lattice generation techniques developed for commercial software applications provide engineers and researchers with multiple options for customising a lattice and a surrounding part without affecting its exterior geometry. Using these proprietary techniques, image-based files can be worked on and meshed to produce watertight export files for AM.
Developments in advanced techniques for designing mechanical structures are significant in continuing to showcase the value of additive manufacturing as a mass manufacturing technique. The demand for lightweight structures and flexible lattice techniques in core industries like aerospace and automotive along with investigation into new materials shows just how pivotal this technique could be for the continued development of the industry.
This article first appeared in the June 2015 issue of TCT Magazine and is available to download free on the the App Store and Google Play.
