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24 May 2018 16:36
6 Important Design Considerations for Metal 3D Printing
Metal 3D printing is on the rise, with sales of metal AM systems seeing an explosive growth of 80% from 2017. Metal 3D printing offers an unprecedented freedom of design, giving designers and engineers the opportunity to create organic shapes and lightweight structures, that would otherwise be impossible with traditional manufacturing methods.
However, to truly unleash the full potential of metal 3D printing and remain competitive, it is crucial to understand how to get the most out of the design capabilities offered by the technology. As traditional design rules can no longer be applied, a new approach to design for metal 3D printing is necessary.
That’s why we’ve put together our top design considerations for metal 3D printing to help you get the most out of your metal parts.
6 things to consider when designing your metal part
1. Wall Thickness
One of the most important point to consider when designing for metal 3D printing is wall thickness. As a general rule of thumb, it is advised to design walls with a minimum wall thickness of 0.4mm. It is important to ensure that the wall thickness of your parts are not too thin or thick, as this can result in either a delicate print or a build-up of internal stresses, leading to cracking. While finer features possible, this is heavily dependent on the metal material chosen as well as the parameters of your printer.
You may also want to experiment with lattice or honeycomb structures in the case of thick walls, as this could save you a considerable amount of material and also reduce build time.
2. Support Structures
Support structures are virtually always a necessity with metal 3D printing. While it is ideal to design a part with the minimum amount of supports necessary, they are required for areas like holes, angles and overhangs. Supports are also used to anchor a metal part to the base plate to draw away heat, which can lead to residual stresses.
The rule of thumb for supports in the inner areas of a part, such as horizontal holes, is to design angled support structures. By applying these structures, you can minimise the contact area with supports, which will in turn result in less post-processing.
In addition to this, design your supports so they taper out as they make contact with the part. This will make supports removal and surface smoothing much easier. Light, tubular support structures will also require far less time and effort to remove.
3. Overhangs and Self-Supporting Angles
At times, you may need to design a metal part with overhangs — the protruding parts of your print. Large overhangs (typically over 1mm) will require support structures to prevent them collapsing during the printing process. The maximum length of an unsupported horizontal overhang is 0.5mm and it is important to keep your overhangs below this length. Fillets and chamfers can be designed into a part to eliminate these overhangs.
In addition to length, the angle of your overhangs are also important to take into consideration. An angle below 45 degrees will typically require support structures.
4. Part Orientation
Experimenting with part orientation is the best way to minimise the amount of support structures needed. For example, if you want to make a metal part with hollow tubular features, horizontal orientation will take up more space, while vertical or angled orientation will save space and reduce the amount of supports needed.
Another consideration to take into account when selecting part orientation is that downward and upward facing surfaces will have different surface roughness (so-called down-skins tend to have inferior surface finish). If you want to produce detailed features with the best accuracy, then make sure to orientate these on the upward facing surface of the part.
5. Channels and Holes
Metal additive manufacturing is notable for its ability to produce parts with channels and holes, which cannot be achieved through traditional manufacturing means. When factoring such features into your design, consider that the minimum diameter for most powder-bed processes is 0.4mm. Holes and tubes larger than 10 mm in diameter will require support structures.
Additionally, perfectly round horizontal holes are still a challenge to 3D print. Consider redesigning such shapes into a self-supporting teardrop or diamond shape.
As hollow metal parts require escape holes to remove unmelted powder, make sure to factor these into your design, with a recommended diameter of 2-5mm.
6. Topology Optimisation & Generative Design
The ability to produce complex geometries using additive manufacturing makes it ideal for topology optimisation and generative design. Topology optimisation aims to optimise the geometry and material distribution of a part using mathematical calculations. Generative design, on the other hand, is inspired by the design patterns of nature, and allows engineers to explore all the possible elements of a solution. By using these tools, designers and engineers can enhance the full range of design freedom afforded by 3D printing, to create functionally optimised, strong and lightweight metal parts.
Shifting the design paradigm to get the most of metal AM
Designing for metal 3D printing is no mean feat, as it requires knowledge about the possibilities and limitations of metal AM technologies and materials, as well as a new approach to design. However, exploring and integrating design guidelines for from the very start of the design process will enable companies to maximise success for the production of end metal parts, while keeping costs and material waste to a minimum.