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How to reduce the weight of AM parts?

Background


Reducing the weight of components and assemblies is often crucial in high-performance applications. In motorsport, it can provide a competitive edge, in aerospace and automotive industries it saves fuel, and in robotics, reducing the weight of the EOAT (end of arm tooling) can enhance speed and precision.


Additive Manufacturing, commonly known as 3D Printing, is an ideal candidate for aiding in weight reduction. Its level of design freedom surpasses many other processes, allowing for unique ways to remove material from designs.




Hollowing


Hollowing a part is the most common and straightforward method of reducing weight. Most parts are hollowed with a basic constant wall thickness, but it is also possible to have thicker walls or internal supports in specific locations to increase strength.


It is important to note that for hollow parts printed with powder bed processes such as MJF (Multi Jet Fusion) or SLS (Selective Laser Sintering), there will always be trapped powder inside the part. Although the weight will be reduced as the density of unfused powder is lower than fused material, to truly optimise the part, consider adding powder drain holes.




A series of cubes showing one solid, one hollow, another hollow but with a hole to drain the powder from and finally a shelled one.



Hollowing can also be combined with internal lattices to increase the part's strength, which is discussed further below.

For more info about hollowing & powder drain holes see the ''Wall Thickness & Hollow Parts'' section of our MJF ordering guide:



Shelling


Shelling is similar to hollowing, except one or more walls are removed. This method is akin to techniques used in moulding or machining. Like hollowing, the part can have thicker walls or internal supports in chosen locations to optimise strength.




Lattices


Replacing sections of the part with lattices reduces weight. Sometimes, lattices are used alongside hollowing, so the inside of the part is replaced with a lattice structure.

A key advantage of MJF over SLS or SLA is that adding a lattice does not increase print time, as there is no laser tracing the shape.



A bracket part with a green gyroid lattice inside it.


Infill Density (for FDM Printing)


Most parts printed with FDM will have an infill pattern. The simplest way to reduce the weight of an FDM part is to lower this infill density, usually expressed as a percentage.

There are various infill patterns available, some offering higher strength while others are faster to print. If weight is your main concern, let us know when we provide a quote, and we can recommend the best parameters to use.



Two 3D printed brackets shown in CAD with a more dense orange infill pattern on the one on the right.


Topology Optimisation


Topology optimisation is the most complex method on this list. In this approach, a computer algorithm determines where to add material within a given design space to meet the part's performance requirements.

There are numerous programs with this feature, with Fusion 360 being one of the most common. We also have an in-house licence for nTopology.



A topology optimised bracket


Material Density


An obvious way to save weight is by switching to a material with a lower density. The final part density is included on the HP datasheet for each material we offer in MJF printing.


For example, PA11 has a slightly higher density than PA12, so if weight is your primary concern, PA12 might be the better option.


However, material density needs to be considered alongside other material properties. A less dense material might seem preferable, but if it is significantly weaker, your part may require thicker walls to compensate. These thicker walls could negate the weight savings of choosing that material.




Conclusion


Whichever weight-saving technique you choose to deploy, we are available to offer design advice alongside our 3D Printing Services.

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