AM in 10 – additive manufacturing and sustainability

Featured image - AM in 10 - additive manufactruing and sustainability

VIDEO SUMMARY

In this “AM in 10” video, we look at improving the sustainability of additive manufacturing (AM) and understand how we as designers can make AM a more sustainable technology. Good knowledge of design (DfAM) can improve the sustainability of AM in so many ways, and excellence among design engineers is key. We’ll also discuss the challenges of sustainability in AM and discuss some ways they can be overcome.

Sustainability essentially means that we as humans can meet our needs without compromising future generations’ ability to meet theirs. By looking at the origin of the word sustain, to ‘sustain’ means to keep something going or provide support. So in many senses, we can understand sustainability as an approach to sustaining life and supporting the planet.

Sustainability consists of three different factors:

  1. Environmental sustainability means that all of the earth’s environmental resources can be maintained for future generations. It means that we are not taking more from the environment than the environment needs to replenish itself.
  2. Economic sustainability is about ensuring that our economic systems can remain in place to sustain future generations.
  3. Societal sustainability is about ensuring that our future communities can remain healthy and secure.

Sustainability - environment, economy and society

In terms of additive manufacturing, it’s important to ensure that the manufacturing techniques we use are sustainable – that when we’re designing and manufacturing components we’re not damaging the planet in a way that’s detrimental to future generations.

Sustainability and polymer processes

One of the key polymer processes that we can look at in terms of sustainability is fused deposition modelling (FDM). The global FDM community of researchers and engineers has taken sustainability to heart and have worked on developing a wide range of materials that are both recyclable and biodegradable. Polymer filaments that are common in FDM such as PLA, are comprised of cornstarch, and degrade naturally in the environment, therefore eliminating some of the challenges that we face with plastic waste.

Polymer filaments made of other natural fibres including hemp, soy and bamboo have also been developed. The increased usage of natural polymer filaments means that engineers can now design new products and 3D print them, reducing the amount of polymer waste that we see in our environment.

Sustainable FDM filaments

Metal additive manufacturing

One of the biggest areas of additive manufacturing is metal AM. However, the sustainability of metal additive manufacturing methods like laser powder bed fusion and electron beam melting is less clear cut than FDM.

In general, additive manufacturing can use four times or more electricity than conventional processes such as milling. Also, generating the additive manufacturing powder for these machines takes more energy to produce than the standard billet of material for traditional machining. This is because of the extra gas atomisation processes, where typically, some of the powder that doesn’t meet the right particle size specification is wasted.

However, there’s more to this debate about electricity usage than meets the eye. It also depends on whether the electricity used for these processes is coming from a sustainable source such as renewable energy.

Sustainability issues of metal additive manufacturing

Energy usage of conventional processes versus additive manufacturing

How do we compare the energy usage or the sustainability of additive manufacturing to conventional processes such as milling? To understand this, we need to clarify an important point:

The energy used in additive manufacturing goes into putting material down (adding) whereas the energy usage for CNC milling or other traditional methods is all about taking material away (subtracting).

One metric that we can use to compare these two processes is known as the ‘buy to fly ratio.’ This term comes from the aerospace industry and we use it to define the amount of material used in the billet of stock material compared to the amount of material used in the final part. We can therefore compare additive manufacturing and conventional machining to the amount of wasted material used to produce a part.

Buy to fly ratio

co2 emissions

This graph below from the AMGTA which has been modified from the Priori Paper from 2017 tells us a lot.

AMGTA graph

The graph demonstrates that the co2 emissions of producing a part is dependent on the geometry of that part- and therefore the design is crucial. On the left-hand side, we can see a component that hasn’t been optimised for additive manufacturing and has a lot of material inside it. In this case, 3D printing the part causes more co2 emissions than conventional CNC machining.

However, as we remove the material from the part, and the amount of material removed (subtracted) from the CNC process exceeds the amount put down (added) using the additive process,  AM becomes a more sustainable process than traditional processes in terms of co2 emissions. Therefore, we can see that design for additive manufacturing (DfAM), and innovative design engineers will have a significant impact on the environmental sustainability of additive manufacturing as a whole.

Sustainability and the aerospace industry

One industry where sustainability can be improved by using design for additive manufacturing (DfAM) is the aerospace industry. Here, even small decreases in the mass of a component by utilising AM techniques such as topology optimisation or lattice structures can reduce fuel consumption significantly.

Conformal lattice

Reducing part failure and maximising printer utilisation

One of the biggest detrimental impacts to the sustainability of additive manufacturing is the number of failures in the part. Essentially, a failed part is a wasted part and the embodied energy that went into creating that failed part is wasted.

Maximising the 3D utilisation and/or the number of parts printed in a single build can also improve sustainability. To achieve this we must consider part optimisation and process optimisation.

Understanding how build orientation impacts the number of parts you can fit onto a build plate is another key DfAM consideration.

3D printing machine utilisation

We offer an online design for additive manufacturing course. This course contains three hours of video material, over 50 pages of online notes and interactive tutorials in our software. By taking this course you can get hands-on learning about build orientation and reducing print failure.

Choice of materials in additive manufacturing

The final thing to consider when looking at the sustainability of metal additive manufacturing is the material choices themselves. Materials like titanium and Inconel have a high embodied energy. This means they take a lot of energy to manufacture. Therefore, if we are using CNC machining and cutting away a lot of that material, essentially all of that energy is wasted.

This is where techniques such as directed energy deposition (DED) can be useful because generating a part that’s near-net-shape can massively reduce the size of the billets we need to create the final parts. These hybrid technologies where we place material close to the desired shape and then machine them back to the right tolerances are going to play a key part in the future of sustainable large metal components.

Four ways of improving the sustainability of additive manufacturing

To conclude what we’ve discussed in this AM in 10 video on sustainability, there are four ways of improving the sustainability of additive manufacturing.

  1. We need to look carefully at the materials. We need less wastage, more recycling and an understanding of the embodied energy in these materials. This way we can fully understand which materials are better for additive manufacturing especially the energy that goes into it.
  2. We need to use good design in a way that improves printer utilisation and maximises the number of parts on that build plate.
  3. We need to use good design to reduce the number of build failures that essentially wastes all the material.
  4. Finally, we need to understand the industries that are impacted most by using AM. This way we can apply the benefits of improved functional design where it can be best utilised to reduce emissions.

Sustainability is a complex concept of which we’ve only touched on a few aspects in this video. I advise you to look more deeply into improving the sustainability of additive manufacturing because it will play a key role in all of our futures as AM designers and AM engineers.