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AM Process Categories

The 7 official AM process categories according to ASTM

A common way to classify technologies is by the 7 main categories defined by ISO and ASTM in the standard 52900-15. We will briefly give an overview of the 7 categories including process description, material categories, typical applications and AM process variants, followed by videos of some of the most common AM processes below. 

Process description: 

A liquid bonding agent is selectively deposited to join powder materials.

Materials: 

Metal and sand

Typical applications:

  • Serial metal parts ≈500-20.000
  • Printing of sand molds

AM process variants – a selected overview

  • Binder Jetting (BJT)
  • Multi Jet Fusion© (MJF)

Process description: 

A focused energy source used to fuse materials as they are being deposited.

Materials: 

Metal

Typical applications:

  • Repair/coating of shafts for oil & gas/heavy duty machinery
  • Aviation Ti parts

AM process variants – a selected overview

  • Laser Engineering Net Shape (LENS)
  • Electron Beam Additive Manufacturing (EBAM)
  • Rapid Plasma Deposition

Process description: 

Material is selectively dispensed through a nozzle or orifice.

Materials: 

Metal, polymer and composite

Typical applications:

  • 3D printing @ home
  • High performance polymers (e.g. PEEK)

AM process variants – a selected overview

  • Fused Deposition Modeling (FDM) – Polymer
  • Arburg Plastic Freeforming (APF) – Polymer

Process description: 

Droplets of build material are selectively deposited.

Materials: 

Metal, polymer and wax

Typical applications:

  • Multicolor/-mate-rial prototypes
  • Wax patterns for jewelry
  • Molds for investmment casting

AM process variants – a selected overview

  • Material Jetting (MJ) – Polymer
  • Multi-Jet Modeling (MJM) (also: MultiJet Printing (MJP), PolyJet) – Polymer
  • NanoParticle Jetting (NPJ) – Polymer

Process description: 

Energy source selectively fuses regions of a powder bed.

Materials: 

Metal and polymer

Typical applications:

  • Polyamer  prototypes
  • Complex metal parts: Implants, fuel nozzle, turbine blades

AM process variants – a selected overview

  • Laser-beam PBF of polymers (L-PBF) (also: Selective Laser Sintering (SLS)) – Polymer
  • LB-PBF of metals (L-PBF) (also: Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), Laser Metal Fusion (LMF)) – Metal
  • Electron beam PBF of metals (E-PBF) (also: Electron Beam Melting (EBM)) – Metal

Process description: 

Sheets of material are bonded to form a part.

Materials: 

Composite, paper

Typical applications:

  • Full color paper prototypes

AM process variants – a selected overview

  • Laminated Object Manufacturing
    (LOM) – Other

Process description: 

Liquid photopolymer in a vat is selectively cured by light-activated polymerization.

Materials: 

Ceramic, photopolymer

Typical applications:

  • Silicone hearing aids
  • High surface finish prototypes

AM process variants – a selected overview

  • Stereolithography (SLA) – Polymer
  • Digital Light Processing (DLP) – Polymer
  • Continuous Digital Light Processing (CLIP) – Polymer
  • Lithography-based Ceramic – Ceramic Manufacturing (LCM) – Ceramic

Videos of selected processes

Additive Manufacturing technologies in action

Below you can find a video explaining the 7 different process categories as well as brief videos of some of the most common Additive Manufacturing processes by hubs. A more detailed explanation of the different processes can be found in the two online learning programs Polymer Technologies and Metal Technologies. 

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Source: CanalDivulgación

Read more about this topic in the AM Fundamentals Course.

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Sinter-based AM technologies and process chain

Sinter-based AM - a technology overview

Many different printing technologies - one sintering process

The sinter-based AM (SBAM) technologies have, as the name suggests, the sintering process in common. In this process, the printed green part is consolidated into a dense part and receives its final properties. The green part can be printed in advance using different technologies.They all have in common that metal powder is bound to the desired shape by a binder. The best-known printing technologies include Binder Jetting and Filament Material Extrusion.

In this section, you learn everything about the sinter-based AM  process chain and get an overview of the different printing technologies.

Goal and structure of this course

This course is aimed at engineers, designers and other professionals that are working closely with sinter-based AM technologies. The goal is to cover the most important aspects that will enable engineers and designers to fully grasp the capabilities and technical limitations of the printing technologies and the sintering process to succeed in technology selection and part design. Besides going through the course from the beginning until the end, this course can also act as a constant source of knowledge while working on AM projects. 

The course is structured into the following sections.

This section will start with an overview of the sinter-based AM process chain and its printing technologies, followed by a technology deep dive into the most important aspects of the BJT technology, followed by a closer look at the debinding and sintering step also including sintering simulation .

The second section will provide an overview of the different materials that are available as well as part characteristics that can be achieved with the BJT process and typical methods for quality assurance. Finally, several common defects in the BJT process are presented. 

The last section will act as a guideline for designers. Besides generally describing the process when designing for Additive Manufacturing, actionable restrictions and guidelines for the BJT process are provided. The final section will present several design examples from different industries. 

What you will find in this section

Sinter-based AM process chain

From digital model to finished part

Data preparation

Simulation to compensate the deformation during the sintering step, nesting of parts and definition of printing parameters

Printing

Through various printing processes, different feedstocks such as metal powders, filaments, pellets or dispersions are processed into green parts

Unpacking

Unpacking of fragile green parts needs to be done carefully and is typically a manual process.

Debinding

Debinding describes the process of removing the binder which results in a brown part

Sintering

To reach the structural integrity of a metal part, a sinter process is required. The powder particles fuse together to a coherent, solid structure via a mass transport that occurs at the atomic scale driven via diffusional forces.

The brown part shrinks ~13-21 % in each direction.

The process chain of sinter-based technologies differs from other AM Technologies. Especially the post-printing processes (debinding and sintering) are crucial to achieve the intended mechanical properties.

Technology principle

How does Binder Jetting work?

Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.

The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.

Working Principle of Binder Jetting

Afterwards the build platform moves downward by the amount of one layer thickness and a new layer of powder is applied. Again, the liquid binder is deposited and hardened in the required regions of the next layer to form the green body. This process is repeated until the complete part is printed. After the complete printing process is finished the parts have to be removed from the “powder cake” meaning the surrounding loose but densified powder. To improve the removal of the excess powder from the green body often brushes or a blasting gun with air pressure are used.

To create a dense metal part the 3D printed green body has to be post-processed in a debinding and sintering process. Similar to the metal injection molding process BJT parts are placed in a high temperature furnace, where the binder is burnt out and the remaining metal particles are sintered together. The sintering results in densification of the 3D printed green body to a metal part with high densities of 97 % to 99,5%, dependent of the material.

Printing Technologies

Metal Binder Jetting

Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.

The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.

Working Principle of Binder Jetting

Material Extrusion

Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.

The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.

Working Principle of Binder Jetting

Mold Slurry Deposition

Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.

The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.

Working Principle of Binder Jetting

Metal Selective Laser Sintering

Binder Jetting is a powder based Additive Manufacturing technology in which a liquid polymer binder is selectively deposited onto the powder bed binding the metal particles and forming a green body.

The metal powder is applied to a build platform in a typical layer thickness of 40 µm to 100 µm. Subsequently a modified 2D print head apply a binder selectively onto the powder bed. Depending on machine technology a hardening or curing process of the binder is performed in parallel for each layer and/or at the end of the whole build. During the in-situ curing process a heat source is used to solidify the binder and form a solid polymer – metal powder composite.

Working Principle of Binder Jetting