Directed Energy Deposition (DED)

Directed Energy Deposition (DED)

Directed Energy Deposition (DED) includes a range of different technologies with varying feedstock (powder or wire) and energy source (laser, electron beam and arc). DED steadily gained importance, especially within heavy industries due to unique capabilities such as high deposition rates, large component production and the ability to build on existing parts. 

In this section, we want to focus on what we consider the two most mature DED processes: Powder Laser Deposition and Wire Arc Additive Manufacturing.

Powder Laser Energy Deposition

Powder Laser Energy Deposition (ED), which is also known as Laser Metal Deposition (LMD), is a welding technology that is known for many years. Recently, more and more AM machine suppliers adopted the technology.

Powder Laser Deposition

Functional Principle

Powder feedstock is blown through a nozzle onto a meltpool that is formed by a laser on a part surface. This process forms raised welding beads and repeats itself until a three-dimensional structure is created. 

2 different technology variants exist: A processing unit with multi axis system and hybrid systems

Processing unit with multi axis system:

The laser beam and the powder supply are combined in a single processing unit, the working head. In a multi axis system typically the working head as well as the substrate plate on which the part is build are fixed to some kind of motion system. The supplier BEAM uses a gantry with five continuous axes for realization of the processing unit’s motion. TRUMPF offers Powder Laser Deposition systems in which the processing unit head is attached to a robot arm. For rotationally symmetric parts, substrate plates can also be fixed to a rotation-tilt table.

Hybrid Powder Laser Deposition Technology

In a hybrid system, such as from supplier DMG MORI, the Powder Laser Deposition process is combined with a subsequent CNC machining. The build platform is movable around two axes and the process unit head around three axes. After a section of part or the complete part is built, a milling head is extended and finishes the as-printed parts’ surfaces.

A powder feedstock is blown through a nozzle into the process zone, where it is preheated by the laser and then absorbed by the melt pool. 

Maturity of Powder Laser Energy Deposition

Technology Maturity Index

4

Powder Laser Energy Deposition display a relatively high technology maturity due to off-the-shelf series machines. However, the technology has not seen significant development during the past few years and is increasingly seeing competition from  related technologies such as Wire Laser Deposition.

Industrialization Index

3,5

Powder Laser Energy Deposition is used for specific applications such as repair of expensive worn-out parts such as turbine blades. The technology however struggles to identify further viable business cases.

Video of the Powder Laser Energy Deposition process

Below you can see a video of the DED process from Italian machine manufacturer BeAM. They use powder as a feedstock and a laser to melt the powder. 

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Wire Arc Additive Manufacturing

Wire Arc Technologies, also known as Wire Arc Additive Manufacturing (WAAM), is based on conventional welding processes such as MIG, MAG and TIG welding. The technology has gained lots of attention due to high build speed and low material costs.

Wire Arc Deposition

Functional Principle

For WAAM, off-the-shelf welding equipment can be used. The wire is fed through a conventional wire-feeding system and is melted by an electric or plasma arc. The motion of the welding torch is provided either by a robotic or gantries system. This way welding beads are placed next to and on top of each other to form a three-dimensional part. 

The wire is fed with a conventional wire-feeding system to the working area. The motion of the welding torch can be provided either by a robotic or a gantries system.

For Wire Arc Deposition, existing, off-the-shelf welding equipment can be used. The welding power is provided by an electric or plasma arc that melts the feedstock to create the weld bead. 

Maturity of Wire Arc Additive Manufacturing

Technology Maturity Index

3,5

WAAM machines are generally a combination of off-the-shelf welding torches with an NC handling system. Therefore, the maturity of machine concepts varies greatly from self-made solutions to turn-key solution. The rapidly growing industrialization, however, is expected to further drive maturity of this technology.

Industrialization Index

3,5

Several niche applications such as fuel tanks in the space industry have further increased the industrial usage of WAAM. One strong driver of the technology is the wide availability of materials since standard welding wired can be used.  

Video of the Wire Arc Additive Manufacturing Process

Below you can see a video of the Wire Arc Additive Manufacturing process from German machine supplier GEFERTEC.

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After gaining a brief overview of Directed Energy Deposition, you can dive deeper into process characteristics as well as typical applications of the process by clicking on the topic below. 

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