Additive manufacturing is a collective term that denotes any production technique by which three-dimensional objects, such as models, patterns, prototypes, tools or final products are built up by the addition of successive layers of a material. Depending on the application and product, these materials may be of liquid, pulverous or solid form, while the template for the construction process in which they are used is supplied in the form of a computer-generated data model, or CAD file. The nature of the production process, which involves creating an object by building it up in layers, is such that no special tools are required and no moulds need to be produced beforehand. Additive manufacturing can be viewed as the inverse counterpart to traditional subtractive processes, such as drilling, milling or turning, in which an object is formed by the removal of material. Additive manufacturing represents one of the three pillars of production technology, together with subtractive and moulding processes.

Alongside the guiding principle of Industry 4.0, additive manufacturing techniques, including 3D printing, are seen as giving a major pioneering boost to the industrial sector and beyond. Greater cost-effectiveness, personalisation and individualisation, lightweight products and above all a hitherto unparalleled forming potential are the central characteristics of additive manufacturing. All of this has created a new way of thinking that manifests itself in an enhanced industrialisation and professionalisation of construction and production processes, which in turn depend on the use of reliable components such as servo drives in the FHA-C Mini series or the CanisDrive® made by Harmonic Drive AG.

Additive manufacturing - a layer-by-layer production process

Before the recurrent process of generating the extremely thin layers (frequently measuring no more than 0.001 mm) can begin, a three-dimensional CAD dataset is created as a construction template. This corresponds with the object to be manufactured, and is typically compiled either with the aid of 3D CAD software or by scanning an existing object. The software divides the three-dimensional object into many layers of equal thickness. In addition to the layer thickness, the dataset also contains the contour dimensions and the numbering of each individual layer.

The essential process of additive manufacturing basically consists of two steps. First of all, a layer is generated on the basis of the information contained in the data, irrespective of the material and the specific choice of additive procedure. In the second step, the current layer is bonded with the previously generated layer, such that the most recently completed layer serves as the base for the next one. Although all such processes employ this sequence, they display differences in both the manner in which the layers are created and the method used to bind the layers together.

Classification of additive production processes

A number of similar generative processes have steadily evolved following the original invention of the additive manufacturing process over 30 years ago. These variations and modifications differ in terms of the material used. Furthermore, a distinction is commonly made between powder bed fusion, production in free space, liquid material processes, and other layering processes.

Stereolithography is an example of a fluid production procedure, and involves the selective hardening of a resin using an ultraviolet laser. Support structures can also be used in stereolithographic production, which make it possible to produce objects with hollows and protrusions.

Fused deposition modelling (FDM) is an example of the free space process. Here, an apparatus containing a heated printer head moves through space following the instructions contained in a construction template. This extruder deposits fine filaments of a plastic, which harden instantly. Fused deposition modelling is a relatively inexpensive additive manufacturing process and is frequently used to produce early-stage prototypes. Users must be prepared to accept a relatively high degree of process imprecision.

So-called laser sintering is a powder bed fusion process. The process uses a powder material, which is gradually hardened by a laser beam in accordance with the required layer contours. Objects made by laser sintering are extremely light, heat-resistant and able to withstand mechanical loads. A wide range of plastics, powders, ceramic masses, moulding sand or paper can be used as initial materials, depending on the type of machine and process and its application field. The choice of material is fundamentally based on the desired property profile of the final product. Attributes such as tensile strength, impact resistance, temperature resistance and form stability can be influenced by the choice of material, as can the product’s appearance and biocompatibility.

With laser sintering in particular, the requirements of additive metal manufacturing procedures are extremely high, especially with reference to the precision with which the individual layers are applied.

Overview of additive manufacturing techniques

  • Powder bed fusion (e.g. selective laser sintering)
  • Free space processes (e.g. FDM or contour crafting)
  • Liquid material processes (e.g. stereolithography)
  • Other procedures (e.g. 3D screen printing)

Additive Options and advantages afforded by additive manufacturing techniques

Advancements in the development coupled with the increased use of additive manufacturing techniques across a wide range of industrial sectors stem from the numerous characteristics and benefits afforded by the technology. While its most significant potential was initially in the construction of prototypes, today a great number of diverse and successful serial applications have been realised. Sectors in which small batch numbers are commonly required and extremely high development costs incurred stand to benefit in particular, as they are now able to produce parts and components with the aid of additive manufacturing, thereby not only saving costs but also enabling relatively prompt production. Pioneering applications can be found in the fields of medical engineering and aerospace technology.

Another characteristic of additive manufacturing is the option that the technology affords to produce individual objects or product solutions without requiring any adjustments or conversions to be performed on a machine or necessitating a change of machine. They enable a manufacturing process in which the production follows on from the engineering, with all the design freedom that this entails. In addition, augmenting traditional production lines with additive manufacturing adds great potential and favours the use of hybrid construction, thus merging the benefits of both procedures. Further characteristics and advantages of additive manufacturing, particularly from an industrial perspective, are its increased cost-effectiveness, optimised life cycle times and production costs, as well as the digitalisation of the process chain.

Furthermore, additive manufacturing makes sparing use of resources and promotes sustainability. Since the latter in particular enables requirements-based manufacturing along with on-site production, storage costs can be eliminated, overproduction avoided, and transport distances and times significantly reduced. 

Additive manufacturing in industry

The enormous variety of machines available for additive manufacturing and the differences between them in terms of their complexity and capability means that the technique can be used not only in industrial applications but also in domestic situations.

The sectors in which additive manufacturing is in widespread use and is accordingly already relatively well developed include the aerospace industry, medical engineering, and the automobile industry. In line with the construction philosophy of maximum weight saving, additive manufacturing enables the production of lightweight components; this necessitates the effectiveness of raw materials, energy and costs. In the field of medical engineering, it is primarily dental laboratories that benefit from the high level of individualisation that is made possible through the use of additive manufacturing techniques; after all no two dentures are alike, and modifications are therefore constantly needed. Furthermore, additive manufacturing makes it possible to integrate new functions in components; this characteristic is of particular importance in the aerospace industry.

Additive 3D printers for domestic use

In recent years, additive manufacturing has been enjoying growing popularity in domestic applications, in particular since the availability of suitable 3D printers. The focus is on printing relatively simple objects, figures and hard components, one reason for this being the relatively low level of complexity and capability of the equipment. Although the use of additive manufacturing techniques requires a certain level of specialist knowledge, pre-configured CAD files and instructions for use enable even untrained users to make their own private 3D prints.

As developments in the field of additive manufacturing continue to progress and advance, its use at home will become more common. It might even be that when a product is purchased, CAD files are supplied with it, to enable spare parts to be printed out. Suitable 3D printers and similar devices are already starting to be found in domestic workshops.

Synonyms

3D printing