Additive manufacturing (AM) is one the the most interesting technological innovations in the manufacturing industry in current times, with the potential to totally revolutionise the way in which we design and create products.

Despite the technology having existed since the 80s, this approach is still in an experimental stage, even though many large corporations have begun implementing it with their business strategy with enormous success.

We are talking about, as we will discuss in detail later, a technology based on 3D printing of an object, via the breakdown of the product into many overlapping layers.

Indeed, additive manufacturing represents the reverse process of so-called subtractive manufacturing, where an object is created by cutting a solid block of material until the final product is achieved, working by a process, as the name suggests, of subtraction.

A suitable comparison at a basic level is the process of sculpting a statue; a marble block is chipped away to remove all that is excess to reveal the desired shape.

AM on other hand, works the other way around. Instead of starting out with a material to cut, the product is built by layering multiple layers of the material in order to achieve the final product.

Let’s take a look at what additive manufacturing is and what are the industrial applications of this production method.

What is additive manufacturing?

As we mentioned, additive manufacturing is a process of creating an object layer upon layer. To do this, generally a 3D printer is used, which is able to print one layer at a time and overlay each one onto the previous layer.

In order to create an object using AM, firstly a technician needs to develop the project, meaning the design, using CAD software.

The software translates the project into a structure that is created layer by layer, which the production machine (the 3D printer) must follow, thus immediately generating the object with a very precise geometric construction.

With this system, it is possible to go directly from the digital project to the physical product, reducing production phases and optimising the various processes.

It is possible to adopt many different types of materials: polymers, metals, ceramic, foams, gels and even biomaterials.

How can additive manufacturing be used?

It is possible to adopt many different types of materials: polymers, metals, ceramic, foams, gels and even biomaterials.

The principal methods are the following:

1. Binder jetting - this method uses a 3D style printing head which moves along axes x, y and z to deposit alternate layers of powder particles and a liquid binding agent.
2. Direct energy deposition - this can be used with a wide variety of materials, including ceramic, metal and polymers. A laser, an electric arc or an electron gun mounted on a robotic arm moves horizontally supplying wire, filament feedstock or powder to build up the material whilst the bed moves vertically.
3. Extrusion - in this process spooled polymers are extruded or drawn through a heated nozzle mounted in a moveable arm. This allows melted material to be built layer after layer. The layers are held together either by controlling the temperature or by chemical bonding agents.
4. Powder bed fusion; this includes a number of AM techniques such as direct laser melting, direct metal sintering, electron beam melting, selective laser sintering and selective heat sintering. The electron guns, the lasers and the thermal printing heads are used to entirely or partially melt thin layers of material, after which residues of excess powder are removed.
5. Sheet lamination which can be subdivided into two technologies:
   1. Laminated object manufacturing (LOM): suitable for creating objects ideal for visual or aesthetic modelling, and are made-up of alternating layers of paper and adhesive.
   2. Ultrasonic additive manufacturing (UAM): this uses thin metal sheets which are joined through ultrasound welding, a low energy/temperature process which can be used with various metals such as aluminium.
6. Vat polymerization - this process uses a vat of liquid resin photopolymers to create layer after layer. Mirrors are employed to precisely direct ultraviolet light which polymerizes the successive layers of the resin via a process of photopolymerization.
7. Additive production using a wire arc or Directed Energy Deposition - Arc (DED-arc) - uses an arc welding source and a robotic welding arm to create 3D shapes via arc deposition. This process often uses wire as the source material, and it follows a predetermined route to develop the required shape. This additive production methodology is usually conducted using robotic welding devices.

The advantages of AM

As explained, via additive manufacturing it is possible to move straight from the digital project directly to the final product, thus reducing time and production costs.

But that is not all. This production technique also has many other advantages, including:

• AM permits the creation of objects which have differing materials on the inside and the outside, as it is developed in single layers.
• With AM, complex geometric shapes are possible.
• It is possible to make small production lots that are economically sustainable, that can be personalised. For example, specific prostheses (such as hearing aids), whilst containing costs at the same time.
• By working on single layers in different materials, the manufacturers can eliminate weight from an object. That is particularly important in the aerospace and automotive industries, where weight can affect the performance of the final product.
• In traditional production, the entire supply chain can take months and require huge investment - sometimes millions or even billions of dollars - which can only be recovered via high volume production. In additive production many steps can be removed, making it lean, fast and economical.

In brief, additive manufacturing can change the way in which objects are produced, optimising processes and becoming a production method that is indeed accessible to small and niche sectors.

Possible applications

Additive manufacturing is potentially applicable to almost any area of industry, but in some sectors, it can really have an incisive effect, such as for the following.

1. Aerospace: AM is particularly suitable for aerospace applications due to its capacity to reduce weight and also to produce complex geometric parts.
2. Automotive: a variety of materials are already widely produced using this process in the automotive field, as they can be rapidly prototyped, bringing down weight and costs.
3. Medicine: the medical sector is finding an increasing number of applications for parts produced using additive methods, in particular for custom-made implants and devices.

These three sectors lend themselves more than others to this kind of production approach for two principal reasons. The first is that in these fields, the functionality of the production piece is more important than the price. The second concerns the necessity to produce small lots, or personalised objects, where additive manufacturing is less costly than traditional methods.

The application of AM can also be extended to the prototyping or pre-series phase of many products, in various other sectors, extending even more its potential.