What is the difference between additive manufacturing and 3D printing?
Patricia Krawczak: Additive manufacturing and 3D printing both refer to exactly the same process; the first term is mostly used by manufacturers, while the second is preferred by the general public. In rare cases it is also referred to as free-form fabrication, in which manufacturing is performed without tools. Initially, the purpose was also to enable rapid prototyping to quickly produce models and prototypes.
What do these two terms mean?
PK: Additive manufacturing refers to a process used to manufacture three-dimensional parts by adding or agglomerating materials based on a digital 3D model. This process transforms virtual objects into physical objects by assembling successive layers of one or more materials. It is seen as a breakthrough technology compared to traditional manufacturing methods such as machining, which removes material to create a finished product. It is a process that does not require the use of specific equipment (molds) to produce objects with complex geometries.
What materials and processes are used in additive manufacturing?
PK: Although polymers account for about three quarters of the market, the majority of the most mature industrial applications involve metals. Yet it is also possible to 3D-print ceramics, glass, sand, earth (clay, geopolymers), food (sugar) and living materials (bioprinting). Although official standards define seven process categories according to the nature and form (liquid, powder, wire or ribbon) of the material used, the deposition technique, and the way in which the material is melted or solidified (laser, electron beam, visible light, ultraviolet or infrared rays, an electric arc or a heat source), in practice each category has many variations.
What is the origin of additive manufacturing?
PK: In the 1960s, additive manufacturing was the stuff of science fiction and futuristic literature, with replication machines and three-dimensional photocopiers. The industrial saga truly began in the 1980s. It is little known fact that it was three French people – Jean-Claude André, Olivier de Witte and Alain Le Méhauté – who filed the first patent application on an additive manufacturing process on behalf of Compagnie Industrielle des Lasers CILAS ALCATEL in July 1984. The trio then fell into oblivion and the patent was abandoned due to a lack of industrial prospects. The American Charles Hull, on the other hand, who filed a patent two weeks later on stereolithography, one of the many additive manufacturing processes, has been remembered by posterity. He is the co-founder of 3D Systems and the inventor of the STL file format that is still used to this day to exchange 3D files.
The main additive manufacturing processes most widely used today emerged 30 to 40 years ago, including selective laser sintering in 1986, the fused filament fabrication process in 1989, and selective laser melting in 1996.
What are the uses of additive manufacturing?
PK: Three main areas have emerged over time among the uses for additive manufacturing. The first is shaping or functional prototyping. The purpose in this case is to rapidly validate a design or concept. The second is the production of shaping tools. This enables the production of molds or mold cavities allowing, for example, to manufacture very large composite material parts in small to medium batches at competitive prices. The third area that emerged about a decade ago is direct production of small-batch parts without tooling.
What are the benefits of additive manufacturing?
PK: The advantage of additive manufacturing is flexibility, including the ability to produce complex geometries that would otherwise be impossible, integrate functions, and customize products. This process also improves agility in the industrialization and marketing of parts by shortening development cycle times (rapid prototyping). It also provides access to new repair solutions by using a scan to manufacture single units of spare parts whose plans or molds are no longer available.
Another benefit is the ability to produce much more lightweight parts thanks to topology optimization, a mathematical method that optimizes the distribution of matter in a given volume that is subjected to a set of constraints.
Finally, additive manufacturing opens up prospects for on-site production, in response to precise needs, which prevents the need for international transport and reduces delivery times. For example, it could provide a valuable solution in conflict zones or in space. NASA has taken an interest in this process for space mission programs such as ISAM (In-Space Servicing, Assembly and Manufacturing) with the aim of manufacturing what the crews need directly in space.
What are the fields of application for additive manufacturing?
PK: The most mature and demanding market is that of aeronautics and space for lightweight designs. Airbus already has over one thousand operational parts despite the cumbersome validation and certification processes that exist in this industrial sector. And in 2022 the Safran Group inaugurated a new industrial site, Safran Additive Manufacturing Campus, a center of excellence dedicated to additive manufacturing located near Bordeaux.
In terms of rail applications, Alstom, the French multinational, is also very interested in additive manufacturing, especially to manufacture spare parts, with the aim of creating a printable parts bank.
Demand is also high in the medical and biomedical fields. Double-digit growth rates are expected in the areas of custom-made prosthetic, orthotic, exoskeleton and implant manufacturing.
Automotive manufacturers also use additive manufacturing, primarily for prototyping. 3D printed car concepts have emerged, in particular with the American company Local Motors, which launched its Strati model in 2015. However, the process is not yet compatible with the high-speed requirements – a pace of one part per minute – for mass-produced vehicles. Meanwhile, Michelin has presented its VISION concept for manufacturing a 3D printed tire with an alveolar structure and airless tread, making it puncture-proof.
The electronics sector also uses additive manufacturing for connected object power systems. The 3D printing of electroactive polymers makes it possible to create flexible energy-independent microgenerators that can even be integrated into clothing if needed.
Additive manufacturing is also present in the construction sector with house and building demonstrators (first in China and Russia and more recently in France) and scaffold-free footbridges and bridges (in Spain and the Netherlands). The goal in this sector is to optimize construction time.
What are the current challenges for additive manufacturing?
PK: The main challenges currently include increasing manufacturing rates, producing very large parts, precision and ensuring the absence of defects, for example, by setting up systems to inspect, monitoring and enable self-adaptive control of machines. There is also a need to improve the surface quality of the parts to avoid post-processing activities such as polishing and sanding. A final issue concerns securing data transfers and intellectual property. The solution to this challenge could be found in blockchain technology, which can be used to control 3D printing files and their delivery processes.
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The scientific community, including IMT researchers, are working on numerous research studies and projects:
- The search for technological solutions to the challenge of integrating fibrous reinforcements in the deposition plane during the 3D printing of structural composites (continuous fibers). The Shoryuken project is exploring the possibility of hybridizing technological solutions by combining laser welding and additive manufacturing.
- Large scale additive manufacturing of XXL parts is performed using polymers and composites with the LASCALA platform, or with cement or concrete.
- Metamaterials (architectured, hierarchical materials with microstructure gradients, sometimes inspired by nature). These artificially structured materials benefit from the intrinsic properties of the materials they contain and from those obtained based on their periodic arrangement in space. It is now possible to take advantage of the new possibilities offered by additive manufacturing to produce extremely lightweight mechanical metamaterials.
- Printed electronics, with the development of durable, flexible and printable self-charging power systems capable of powering a wide range of sensors used in automotive vehicles.
4D printing to create dynamic objects that actively respond to external stimuli. In other words, changing the shape of 3D objects once they have been printed, in response to the effects of a stimulus (temperature, light, humidity, electric field). Two IMT researchers are jointly editing a special issue of the Materials journal, which is open to contributions, on the latest advances in this field.
