| Glossary | Technologies | Additive manufacturing/3D printing

Additive manufacturing/3D printing

Definition and differentiation

Additive manufacturing and its manufacturing processes are characterised by the fact that the components are generated by adding, applying and depositing material. The decisive factor here is that the components are built up additively from individual layers. A digital 3D model from CAD design software is used directly to generate a physical component. This is used to generate both the mechanical and technical properties as well as the geometry and shape of the components in the process of building up the component layer by layer.

In German, the term 3D printing is used as a synonym for this type of component manufacturing, although 3D printing only describes a single additive manufacturing process (binder jetting). Compared to formative manufacturing processes, additive manufacturing does not require moulds and models, which can be a major cost driver, especially for customised production. Examples of this are injection moulding or forging. Compared to subtractive manufacturing processes such as turning, milling or drilling, additive manufacturing processes do not require prefabricated workpieces (semi-finished products). In addition, additive manufacturing without tools, such as drills, milling heads or turning tools, allows greater creative freedom. Components with a high level of complexity, such as internal cavities and undercuts, can be produced economically using additive manufacturing processes, which is often not economically or technically feasible using formative and subtractive manufacturing processes.

In addition to this potential for a high degree of design and construction freedom, additive manufacturing is characterised by high material efficiency, as only the material required for the subsequent intended use is applied layer by layer. Table 1 shows the specific potential of additive manufacturing in relation to the component, production and business model[1].

Component-relatedProduction or business model-related
Integration of functions and sensors into the structure of the componentsFlexibilisation of production through decentralised production on demand and on site
Optimisation of component functions, e.g. in relation to thermal managementprototypical production of small batch sizes to shorten time-to-market
Lightweight optimisation of components through mould and material lightweight constructionReduction of material waste
Increasing material efficiencyReduction of set-up and assembly times
Consolidation of components from assembly-intensive assembliesReduction of delivery times as well as storage and logistics costs through decentralised production
Table 1: Potential of additive manufacturing in terms of the components generated and the associated manufacturing and business models

The potential can be utilised using a variety of different additive manufacturing processes. Table 2 provides a systematisation of the single-stage additive manufacturing processes based on the type of material and the starting material in accordance with DIN EN ISO 52900:2022. There are many different names for the individual machine technologies for the process categories. Therefore, only one exemplary machine technology is named in this table.

Type of material
Material
Starting materialProcess category
(exemplary
machine technology)
Example materials
MetalsFilament/wire materialMaterial application with directed energy deposition (DED)Stainless steels, titanium and nickel-based alloys
Powder materialpowder bed-based melting (selective laser melting (SLM))Stainless steels, titanium, aluminium, nickel-based alloys
PolymerFilament/granulate materialMaterial extrusion (fused filament fabrication FFF; fused deposition modelling FDM)Thermoplastics (e.g. ABS, PLA, PP), high-performance plastics (e.g. PEKK, PEEK)
liquid materialFree jet material application (material jetting)Thermoplastics (e.g. ABS, PLA, PP)
Powder materialpowder bed-based melting (laser sintering SLS)Polyamides, PEKK, filled plastics
Free jet binder application (High Speed Sintering (HSS))Polyamides
liquid materialbath-based photopolymerisation (stereolithography (SLA))Synthetic resins, UV-sensitive liquid plastics
Gypsum, sand, etc.Powder materialFree jet binder application (binder jetting, 3D printing)Sand, gypsum, inorganic materials
Table 2: Selection of process categories and materials that can be processed using additive manufacturing processes in accordance with DIN EN ISO 52900

History of additive manufacturing

The development of additive manufacturing processes began in the 1980s with the first additive manufacturing process of stereolithography[2]. From the 1990s onwards, these were then used operationally, particularly for the production of prototypes (rapid prototyping). In the early 1990s, Germany pioneered the additive manufacturing of metal components and has further expanded this technological pioneering role in recent decades. As a result, Germany is a leading market for technology providers and technology users of additive manufacturing.

Application and examples

The diverse potential of additive manufacturing has favoured the further development of application areas and additive manufacturing processes in recent years and decades[3]. Four areas of application for additive manufacturing can be distinguished along the typical product life cycle[3,2]:

  • Rapid prototyping: Production of prototypes and models in reduced quantities in various forms of series proximity and functionality, such as design, geometric and functional prototypes
  • Rapid tooling: Production of complex tools, tool inserts and moulds for conventional series production
  • Rapid manufacturing: production of end products suitable for series production. This allows components suitable for series production to be manufactured for the end application as part of the production process.
  • Rapid repair: production of sporadic spare parts and repair of worn components in after-sales service

In recent years, rapid repair has increasingly been used in industrial series production in addition to its previous main application in prototype production. This is particularly evident in the medical technology sector (for endoprostheses/implants or exoprostheses), the aerospace industry (retaining elements in aeroplanes, injection nozzles in engines) and mechanical engineering (production aids, robot grippers). In addition, additive manufacturing processes are becoming established for use by end customers, such as automotive (interior trims or injection moulds) or sports technology (functionalised shoe soles, individualised bicycle saddles). In the future, further applications are expected in the areas of food production (meat and meat substitute products) and building construction (residential and public buildings).

To summarise, additive manufacturing is used in particular for small batch sizes and quantities of geometrically and structurally complex components. Here, additive manufacturing can achieve a particular economic advantage compared to conventional manufacturing processes.

Criticism and problems

Despite at least 30 years of development for many additive manufacturing processes, there are industrial niche applications of additive manufacturing, but a truly broad industrial application is not yet recognisable. In many cases, the degree of industrialisation of individual additive manufacturing technologies and machines does not yet meet the core industrial requirements for reproducibility of component quality, process robustness and the degree of automation of the entire process chain. This process chain includes not only the additive layer application but also the software-supported design and simulation in process preparation as well as the removal of support structures in component post-processing, some of which are necessary due to the process. Among other things, this results in specifically high component costs, which is currently one of the obstacles to additive manufacturing. This obstacle to economic efficiency is further exacerbated by high material and machine system costs.

Research

In recent years and decades, strong interdisciplinary research by universities, research institutions and companies, particularly in Germany and Bavaria, has led to new applications and more resource-efficient processes. For example, research is being conducted into application-specific materials for additive manufacturing technologies, which can also be processed together as a multi-material approach[4]. New additive manufacturing technologies or the further development of existing ones are also a focus of research. In particular, the focus here is on reducing the previous obstacles to industrialisation: productivity, automation and quality assurance.

In recent years, increased research activities have been observed with regard to the additive processing of renewable or biodegradable plastics or waste materials, as well as the increase in resource efficiency and environmental management of individual processes in the additive process chain [5][5].

One approach to effective research and further development of additive manufacturing is the interdisciplinary collaboration of various experts from different perspectives. In 2020, for example, the University of Bayreuth founded an interdisciplinary think tank “Campus Additive.Innovationen”, in which over 30 chairs from five disciplines are working on making the future potential of additive manufacturing tangible and researching it[6].