Additive manufacturing towards a flexible, sustainable and smart industry

A radar mount designed for a drone that weighs 60% less whilst delivering the same performance.

An aircraft engine redesigned to reduce the number of components from 830 to 13.

Systems that can monitor the optimal quality of parts during the production process itself, drastically reducing the proportion of rejected products.

These are just a few examples showing the progress achieved through additive manufacturing – also known as 3D printing.

But let’s forget about 3D printers used to make fun little plastic objects. Originating from 3D printing for prototyping, additive manufacturing is now a sophisticated and rapidly developing technology that is increasingly used in industrial production systems: as the name suggests, it is a manufacturing technique based on adding material, rather than removing it, to produce objects with the desired geometries.

In this field of research, Politecnico di Torino is at the forefront, starting with the IAM@PoliTo Interdepartmental Centre (Integrated Additive Manufacturing Centre). As Luca Iuliano, Professor at the Department of Management and Production Engineering (DIGEP) and Coordinator of the Centre, explains: “IAM@PoliTo is one of the few research centres in Europe where the additive manufacturing process is monitored and studied from every angle, from the initial concept to final testing: design, materials research, technical solutions, and monitoring during production – we oversee everything, right up to the testing of products using industrial tomography.” Technology transfer is facilitated by the CIM 4.0 Competence Centre, which is responsible for developing the proofs of concept developed at IAM into production-ready solutions.

This is a highly multidisciplinary field: in addition to Iuliano, we met Paolo Fino, Professor at the Department of Applied Science and Technology (DISAT); and Federica Bondioli, Professor at DISAT and Head of Spoke 6 (Additive Manufacturing) within the MICS Extended Partnership – Circular and Sustainable Made in Italy, funded by the Ministry of University and Research (MUR) as part of the National Recovery and Resilience Plan (PNRR), with Next Generation EU funds.

Digital, connective and sustainable: these are the watchwords of the industry of the future, as it evolves before our very eyes. Industry 4.0 – the fourth industrial revolution – marks the shift towards increasingly intelligent production techniques, thanks to the integration of advanced digital technologies. We are talking about the Internet of Things (IoT), devices capable of connecting to the internet to exchange data with other devices and systems; about artificial intelligence; about digital twins, digital replicas capable of reproducing complex devices in digital form, for example to enable remote control; about cyber-physical systems (CPS) for the real-time monitoring and adjustment of production systems. All these technologies are converging towards a highly automated industry, in which the interconnection between machines, operators and systems enables a continuous flow of information, allowing production processes to be optimised.

Additive manufacturing plays a key role in this scenario: by enabling the production of objects from digital models, created layer by layer, and thus eliminating traditional material-removal processes, it significantly reduces waste and optimises the use of materials, thereby contributing to sustainability.

As Iuliano explains: “Essentially, this method allows us to move from a three-dimensional CAD model – that is, a file created on a computer – to a physical object without using conventional machine tools: we bypass a whole series of steps associated with conventional technologies.”

Several factors contribute to the sustainability of this technology, an aspect that is highly valued at Politecnico di Torino.

• Resource efficiency: the production process generates very little waste as it uses only the material required for the final shape.
• Lower energy consumption: to produce medium-sized components, an additive manufacturing machine requires an installed power of around 5 kW, whereas an equivalent foundry would need several megawatts.
• Production centre location: the machines produce zero emissions, comparable to those of an extractor hood, allowing production centres to be set up even in urban areas, thereby eliminating the environmental impact typically associated with heavy industrial zones.
• Circular economy: the technology makes it easier to repair worn components, restoring only the damaged part instead of replacing the entire piece.

Furthermore, additive manufacturing enables the production of complex, customisable objects, allowing for the creation of hollow shapes or internal geometries that would be impossible to achieve using conventional production techniques, thereby delivering significant benefits in terms of functionality and efficiency.

“We mustn’t assume that 3D printing is destined to completely replace traditional manufacturing processes,” warns Luca Iuliano. “Rather, it complements them. It would be neither practical nor cost-effective to use it to produce simple objects such as, say, metal plates with four holes. It is a sophisticated technology, particularly suited to two applications: when complex shapes are required – shapes that are impossible or very difficult to achieve using conventional techniques – and when production runs are limited.”

This is why the aerospace and medical sectors are currently the most impacted.

Iuliano adds: “The aerospace industry requires components that are both particularly complex in terms of shape and structure, and as light as possible, given that they have to fly: two areas in which additive manufacturing offers significant advantages. Just to mention one, at the IAM@Polito Centre, thanks to this technique, we have managed to produce a radar mount for a drone that is 60% lighter than the equivalent produced using traditional techniques. As for the medical sector, consider the field of anatomical prostheses, where we need to produce objects that are both complex and customised, as they are tailored to the individual patient: in this case, it is effectively single-unit production, so additive manufacturing is truly the most effective solution.”

Another sector that has shown considerable interest for several years is the racing industry, particularly Formula One, again due to the need for complex, durable, lightweight parts produced in limited quantities. “It has been used for years in the field of motor racing. More recently, in the context of technological innovation within the automotive sector, additive manufacturing is also establishing itself as a strategic solution for the design and production of high-performance components, particularly in the premium and luxury segments, where lightness, customisation and structural optimisation are key factors.”

Iuliano is adamant about one thing: the final quality of the products. “I often say that we mustn’t assume additive manufacturing is inferior in terms of material quality. Indeed, when processes are well controlled, the mechanical performance and quality of manufactured components are even better – in fact, they are certainly superior to those produced using conventional methods.”

What are the main challenges facing this technology today?

Overcoming the limitations arising from its intrinsic properties, which stem from its having been developed for prototyping – that is, by definition, very small-scale production.

Iuliano explains: “When it first emerged in the late 1980s, it was a technology designed for prototyping. Even today, the machines are based on that old philosophy and are not fully automated. Systems designed for prototyping are ill-suited to larger-scale production: this is an area that needs further work. Even the machining monitoring systems are still in their infancy. We can say that the main focus is on developing new generations of machines that are more productive, enabling increased volumes and gradually making this technology viable for larger-scale production as well.”

Materials research is a crucial field. Compared to the options available for conventional technologies, we still have relatively few materials available for additive manufacturing. This is another focus of research at Politecnico, where experts from all sectors work in close collaboration.

We spoke to Paolo Fino, Professor and member of IAM@PoliTO, where he specialises in materials: “Politecnico di Torino is one of the very few universities equipped with a spray dryer, which allows us to produce the metal powders required for additive manufacturing. We are able to create alloys exactly as we want them, to understand them thoroughly, including all the required analyses. We have access to all existing technologies, including prototyping, along with all the expertise needed to design and redesign test pieces, samples, prototypes… anything. We can optimise them all and proceed with the due testing phases. One of our strengths is interdisciplinary collaboration, which gives us a very broad perspective on the subject and a competitive edge precisely because of this vision of the future. Materials, indeed, can only evolve alongside technology.”

What are the main objectives of materials research today?

Firstly, to increase them. Fino continues: “The key goal is to broaden the range of materials that can be used with various additive manufacturing technologies as much as possible. Right now, in the field of metallic materials, we have between 100 and 150 usable materials – a drop in the ocean when you consider that there are millions of metal alloys; technically, there could be at least a thousand times as many. So, we are working to expand the number of materials and improve their workability with additive technologies, to better understand the material’s characteristics after processing, and to determine which types of technology to use to achieve the desired results. From the perspective of polymeric materials, the same applies: but in this case, a process can be applied that is somewhat similar to the reuse of traditional thermoplastics, thereby greatly expanding the range of available materials; I expect major developments in this field.”

Additive manufacturing, even in the field of metallic materials, faces several challenges related to the heat required for processing. The main enemy has a name: thermal stress.

Fino explains: “During printing, we encounter extreme temperature gradients: within just a few millimetres, the temperature drops from the melting point of 1500°C to the ambient temperature of the print chamber. If heat dissipation is not managed properly, the hot layers that cool down on top of layers that are already cold tend to contract and tear, causing warping or fractures. To solve this, we are exploring the possibility of using the laser not only to melt the material, but also to preheat the printing chamber area, thereby reducing the temperature jump. Alternatively, if an electron beam is used for melting instead of a laser, it is first controlled like a spray and then like a tap: before melting the section, the beam is ‘defocused’ to cover a wider surface; this transfers heat to the entire printing bed; it is then narrowed to perform the melting, once the surface is already hot, thereby eliminating thermal stress between the layers”.

There are also cases where additive manufacturing can solve problems by enabling the use of alloys that cannot be used with conventional systems: “In traditional foundries, it is not possible to combine elements with very different densities; this would result in a separation similar to that between water and oil, with the heavier elements sinking to the bottom. Additive manufacturing solves this problem by melting micro-volumes of powder (100–200 microns) in a very short time: the material does not have time to stratify and solidifies into a perfectly homogeneous alloy. A case study of global significance, however, was that of the aviation blades developed for aircraft engines by General Electric-Avio. They were made from an extremely lightweight material, ideal for the aerospace sector, but relatively fragile and hard to handle using conventional casting. In traditional foundry processes, the microstructural defects were such that only one in six blades could be salvaged (a yield of 16%). By switching to additive technology, the precision of the process made it possible to drastically reduce defects, bringing the yield up to five out of six blades: and this was achieved using the same material, simply by changing the technology.”

A particularly relevant case in everyday life concerns the use of additive manufacturing to produce titanium pasta dies, intended to replace traditional bronze ones, which have the drawback of containing copper and are therefore prone to rapid degradation. Fino explains further: “Traditionally made of bronze, these dies are subject to rapid wear due to abrasion caused by the dough; erosion of just a few hundredths of a millimetre is enough to alter the thickness of the pasta, subsequently ruining the drying process. Producing these dies by traditional methods involves machining solid metal bars, discarding up to 80% of the material as shavings. With additive manufacturing, it is possible to use just the amount of powder required, reducing waste, whilst also utilising titanium—an inert and extremely durable material—to create internal curves and sharp edges that would be impossible to achieve with a milling cutter.”

“In fact, we should not refer to additive manufacturing in general terms: we are, rather, dealing with a set of technologies, each of which is suited to different materials and applications.”

The answer comes from Federica Bondioli, Professor and member of IAM@ PoliTO. She coordinates Spoke 6, which is dedicated to additive manufacturing within the MICS partnership. The aim of the research is to capitalise on the characteristics of this technology to apply it specifically to sustainability, creating a new generation of products that are more sustainable, zero-waste, customisable and suited to supporting a circular economy, and usable in many different fields, from jewellery to car components to furnishings. Products that, thanks to this technology, can be repaired rather than replaced, are easy to recycle, and have a low environmental impact throughout their entire life cycle.

As Bondioli explains, additive manufacturing involves various technologies. When it comes to metallic materials, we can essentially split it into two main categories:

• Powder bed fusion (PBF) technologies, in which a laser (L-PBF) or an electron beam (EB-PBF) melts extremely thin layers of powder that have been deposited beforehand
• Direct energy deposition (DED) technologies, in which the material is melted as it is deposited onto the substrate.

Powder-based technology, in particular, offers great flexibility of use, making it an attractive option for repair work, thereby extending the lifespan of products.

Bondioli explains: “Additive manufacturing makes possible a so-called double revolution towards digital and sustainable production: a digital revolution, because the process always starts with computer models, which can be tailored and created ad hoc; a sustainable revolution, because this approach means placing material only where it is needed. It is a completely different philosophy: whereas in traditional subtractive manufacturing, material is removed, aiming to take away as little as possible to save machine time and labour, in additive manufacturing only the essentials are added: this results in lower use of raw materials and less production waste, to the benefit of sustainability”.

Among the projects included in Spoke 6, coordinated by Federica Bondioli, we would like to highlight three.

• The Green Brake System project is developing an innovative braking system capable of reducing PM10 emissions in line with the new Euro 7 regulations. The aim is to reduce dust emissions from the braking system by more than 65%. This is achieved by applying a specialised coating to the standard cast iron brake disc using an additive manufacturing technique.
• The project “The direct/indirect use of additive manufacturing in construction viscous mixtures” explores the construction and design potential of additive manufacturing technology using viscous materials in the fields of civil engineering and architecture. The project involves the creation of two demonstrators – namely, outdoor furniture items – with the aim of achieving an optimal balance between the products’ technical performance and their environmental impact.
• The Mat4Fashion project aims to investigate the machinability of metallic and ceramic materials using various additive manufacturing technologies, with the aim of creating designer jewellery and accessories. These technologies enable us to overcome the limitations imposed by traditional methods such as lost-wax casting or manual craftsmanship, allowing artisans and industry experts to experiment and bring their ideas to life without constraints related to the piece’s geometry, whilst offering the possibility of designing unique and fully customisable items.

The application of in-situ inspection systems during production is also a key aspect, in terms of additive manufacturing’s contribution to sustainability, as it helps to reduce waste caused by errors during the process. Bondioli explains: “A whole range of sensors can be incorporated, such as cameras and infrared thermal cameras, which monitor the part as it is being built, so that production can be halted the moment a defect appears: this once again leads to less waste and greater sustainability”.