The 7 process categories of additive manufacturing

Autor: David Rodríguez
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13 September 2021

Additive manufacturing is based on stacking successive layers of material, but there are different ways of doing this to create the final three-dimensional shape. Depending on the type of energy used to transform the raw material and the technique used to add these layers, there are 7 main families, defined in the ISO 17296-2:2015 standard, which encompass the 3D printing ecosystem.

It should be noted that this is a very general grouping, as each family may include techniques that differ from one another, mainly due to the need to patent the technology. We will look at the principle of operation, the field of application, the possible materials to be made and the main companies in their area, and we will leave the sub-processes for a post on each one in particular, as the details make the difference.

Binder Jetting

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which a liquid bonding agent is selectively deposited to bind powdered materials. (ISO 52900:2015)

Primary bonding by chemical reaction of the adhesive. Secondary bonding for certain materials (especially metals) in the form of heat treatment to obtain the final properties.

Characteristics of the process

  • Without supports, the powder itself acts as a support
  • Possibility of obtaining coloured parts
  • Good aesthetic quality
  • Enormous dimensional shrinkage in case of metals due to sintering
  • High manufacturing speed
  • Medium to high equipment cost
  • Low cost per part
Dimensional shrinkage of parts after sintering. Via P. Calves, CETIM

Materials

Metals, plastics, ceramics, composites, wood, glass, sand and gypsum. Presented in powder.

Applications

  • Medium-low production batches
  • Colour prototypes
  • Metal parts with low mechanical load requirements
  • Diversity of sizes, although in the case of metals, small, non-massive parts

Companies

3DSystems (Z Corp), Desktop metal (now includes ExOne), Voxeljet

Desktop Metal’s Shop System with its sintering furnace. Via Desktop Metal.

Directed Energy Deposition

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are deposited. (ISO 52900:2015)

Energy source in the form of a laser, plasma, electric arc or electron beam. Fusion of the material and subsequent solidification.

Sequence of production of a part. Via Bernardo Freire et al.

Characteristics of the process

  • Without supports, the material is always fed to the normal of the working plane
  • High deposition rates
  • The platform has several degrees of freedom, unlike other technologies where it only moves in the Z axis
  • High cost

Materials

Metallic, ceramic. In filament or powder form.

Applications

  • Hybrid manufacturing
  • Building materials
  • Repairs
  • Coatings
  • Large parts
  • Multi-material parts
Reconditioning of a worn crankshaft of a ship’s diesel engine by DED. Via H. Koehler et al
Result of the work, injection bore and opposite side. Via H. Koehler et al

Companies

Trumpf, Optomec, DMG Mori, Sciaky Inc, Norsk Titanium, MX3D

Material Extrusion

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which material is selectively dispensed through a nozzle or orifice. (ISO 52900:2015)

The material is melted in the nozzle to pass through the orifice and is deposited on the platform or material of the preceding layer. The platform moves in the Z-axis and the nozzle moves in the X-Y axis.

The source of activation can be heat or ultrasound and the binding mechanism is mainly thermal, although there is also the possibility of finding technologies that bind by chemical reaction.

Characteristics of the process

  • Slow process
  • Affordable desktop printers in terms of price, size and performance
  • In the case of industrial machines medium-high cost
  • Low aesthetic quality
  • Adjustable infill. Possibility to parameterise the filling of the part walls.
  • Simple operating principle
  • Easily scalable, no technical size limitation

Materials

Thermoplastics, metallics, composites, in the form of filament (coil) or pellets.

FDM part in ULTEM 1010. Via Stratasys.

Applications

  • Prototypes
  • Spare and replacement parts on site
  • Single or very low volume production batches
  • Parts with technical plastics

Companies

Stratasys, Makerbot, Prusa, Ultimaker, Desktop metal

Ultimaker Original, desktop printer “do it yourself”. Via Ultimaker

Material Jetting

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which droplets of building material are selectively deposited. (ISO 52900:2015)

The liquid material is deposited linearly through nozzles (buses) and bonded by chemical reaction activated by a light source (for photopolymer resins) or by solidification of molten material (waxes).

The head containing the buses moves in X-Y mechanically, so the precision in these axes is constant.

Characteristics of the process

  • Possibility of printing multi-materials on a single part.
  • Printing in colour and with different textures available
  • Technically there is no limitation of print size
  • Very fine details
  • Medium-low cost
Torch prototype. Via Stratasys.

Materials

Plastics (thermosets), metallic and waxes, generally in liquid state.

Applications

  • Plastic prototypes with various hardnesses and flexibilities in the same part
  • Product mock-ups
  • Models for lost wax casting. Jewellery

Companies

Stratasys (includes Solidscape), 3D Systems, Xjet (metal)

Stratasys Objet500 Connex3. Via Stratasys.

Powder Bed Fusion

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which thermal energy selectively fuses regions of a powder bed. (ISO 52900:2015)

A source of thermal energy (laser, infrared lamp or electron beam) impinges on a surface of material that has been contributed by a blade or a roller. The material is bonded together by the chemical reaction caused.

The activation source designs the layer in the X-Y axis and the platforms (construction and material supply) move in the Z axis.

Characteristics of the process

  • Work in controlled atmospheres (O2 and temperature)
  • In the case of plastics, we work without supports and use the entire volume of the XYZ chamber
  • In metals, the management of the supports is a critical factor
  • It is possible to rework the parts (hybrid manufacturing)
  • Very wide range of metal alloys
  • Complex and costly process
Cranial plate case study. Via Renishaw

Materials

Thermoplastic polymers and metal alloys in powder form.

Applications

  • High value-added end parts
  • Functional parts for regulated applications: aeronautics, aerospace, medical, automotive, etc
  • Low or unit batches

Companies

HP, EOS, Renishaw, General Electric (Concept Laser, Arcam), SLM Solutions, 3D Systems

EOS M290. Via EOS.

Sheet Lamination

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which sheets of material are joined together to form an object. (ISO 52900:2015)

The sheets are stacked on a work surface where they are joined in layers and formed. The joining method may be adhesive by chemical reaction, ultrasonic welding or thermal energy. The contour of the plane in question is then cut out and the next layer is added.

Characteristics of the process

  • High deposition rates per volume
  • Allows for combinations of materials
  • Embedded components can be included
  • Moderate machinery and operating costs

Materials

Paper, cardboard, plastics, composites and metals, all in sheet form.

Parts made in paper. Via Clean Green 3D.

Applications

Aesthetic and visual models

Companies

Clean Green, Envisiontec (now part of Desktop Metal), Impossible Objects

Impossible Objects CBAM-2. Via Impossible Objects

Vat Photopolymerization

Via ISO 17296-2:2015

Definition and principle of operation

Additive manufacturing process in which liquid photopolymer in a vat is selectively cured by light-activated polymerisation. (ISO 52900:2015)

A tank filled with photopolymer resin receives UV radiation from a laser (spot impact along the X-Y axes) or a lamp (impact in the entire X-Y plane). The liquid resin (monomers) solidifies through the chemical reaction of polymerisation on a platform that either sinks into the tank or rises away from it.

Characteristics of the process

  • Diversity of resins, especially in DLP
  • High manufacturing speeds of DLP, traditional SLA is slower
  • Office/home equipment available
  • High surface and detail quality
  • Medium to high cost for industrial equipment

Materials

Photopolymer resins (thermosets). Liquid state.

Applications

  • Prototypes, mock-ups and models. Easily treatable by hand for finishing and painting
  • Master for vacuum casting (duplication)
  • Final part not subjected to high loads or excessive outdoor exposure
Carbon3D sole for Adidas Futurecraft 4D model in EPU 41 material. Via Carbon3D.

Companies

3D Systems, Envisiontec (now part of Desktop Metal), Photocentric, Formlabs, Stratasys (Origin)

3D SystemsProX 800. Via 3D Systems.

REFERENCES

Cover image, author’s collage, source:

MX3D

Carbon

  • ISO 17296-2:2015 Additive manufacturing — General principles — Part 2: Overview of process categories and feedstock
  • ISO/ASTM 52900:2015 Additive manufacturing — General principles — Terminology
  • O. Diegel, A. Nordin, D. Motte. A Practical Guide to Design for Additive Manufacturing. Springer (2019)
  • M. Puerto Pérez-Pérez, Miguel A. Sebastián, Emilio Gómez-García, Análisis y propuesta para la utilización de los contenidos en normas técnicas para la enseñanza de la Fabricación Aditiva, presented at XXII Congreso Nacional de Ingeniería Mecánica, Madrid, Spain, 19-21 Sept 2018
  • A. Danut Mazurchevici, D. Nedelcu & R. Popa, Additive manufacturing of composite materials by FDM technology: A review, Indian Journal of Engineering & Materials Sciences, 27, 179-192, April 2020
  • P. Calves, Metal Binder Jetting une opportunité pour la production de petits composants complexes en petite et moyenne série, Traitements & Matériaux, 452, 50-56, Mai-Juin 2018
  • B. Freire, M. Babcinschi, L. Ferreira, B. Señaris, F. Vidal & P. Neto,Direct Energy Deposition a complete workflow for the additivemanufacturing of complex shape parts, Procedia Manufacturing 51, 671–677, Jun 2021
  • H. Koehler, K. Partes, T. Seefeld & F. Vollertsen, Laser reconditioning of crankshafts: From lab to application, Physics Procedia 5 387–397, 2010

David Rodríguez

3D Printing professional. Mining & Energy Engineer B.Sc. Industrial Engineer M.Sc. Believe to make.

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