Difference Between Filament Feed and Powder Fed Direct Energy Deposition

Directed Energy Deposition

Directed energy deposition is defined as "an additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited."

From: Power Ultrasonics , 2015

3D printing of metals in rapid prototyping of biomaterials: Techniques in additive manufacturing

S.L. Sing , ... Wai Yee Yeong , in Rapid Prototyping of Biomaterials (Second Edition), 2020

2.2.2 Directed energy deposition

DED is a group of AM processes that adds material alongside the heat input simultaneously. The heat input can either be a laser, electron beam, or plasma arc. The material feedstock is either metal powder or wire. Powders result in lower deposition efficiency compared with metal wires as only a part of the total powder would be melted and bonded to the substrate (Lee, 2008). Like the E-PBF, electron beam systems in DED require vacuum and would not have high oxidation issues and laser system and, on the other hand, require other methods to introduce inert gases. Powder DED machines often have inert gas blown together with the powder from the nozzles, thereby sheathing the melted region, reducing the oxidization rate (Gokuldoss et al., 2017). Powder DED systems can use single or multiple nozzles to eject the metal powders (Mazzucato et al., 2017). Using multiple nozzles allows the possibility of mixing different materials to get functionally graded materials (FGM) (Liu and DuPont, 2003; Li et al., 2017). A schematic of the DED systems are shown in Fig. 2.4.

Fig. 2.4. Schematics of two DED systems (A) uses laser together with powder feedstock and (B) uses electron beam and wire feedstock.

DED systems can differ from PBF systems as powders used are often larger in size and require higher energy density (Yusuf and Gao, 2017; Lewandowski and Seifi, 2016). This results in faster build rates as compared with PBF system. However, this leads to poorer surface quality that may require additional machining. Support structures commonly used in PBF systems is seldom or never used in DED that often uses multiple axis turntables to rotate the build platform to achieve the varying features. Without the need for a powder bed, DED systems can do repair or printing on existing parts.

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3D and 4D Printing of Functional and Smart Composite Materials

Ester M. Palmero , Alberto Bollero , in Encyclopedia of Materials: Composites, 2021

Directed Energy Deposition

Directed Energy Deposition (DED) allows for the creation of objects by melting the material (most frequently used for metals such as titanium, aluminum, stainless steel or copper) in powder or as a wire with a focused energy source as it is deposited by a nozzle on a surface ( Ashish et al., 2019). In a DED printer, the nozzle head moves around a fixed object for depositing the material in specific locations (Shamsaei et al., 2015; Thompson et al., 2015). Despite it is possible to build full parts with DED techniques, they are typically employed for repairing or adding additional material to existing objects. When combined with CNC machining in a single hybrid equipment, DED results in a powerful technology for obtaining a precise finish of the built part. DED also shows some drawbacks as the requirement of a large volume of inert gas when a fully inert chamber is needed; the necessity of post-processing for reaching the desired finish of the manufactured part; and the wasted material when not all the material sprayed by the nozzle is melted, reducing the efficiency of the technique (Zenou and Grainger, 2018).

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Quantification and certification of additive manufacturing materials and processes

Chang-Jun Bae , ... Arathi Ramachandran , in Additive Manufacturing, 2018

2.3.3.8 ASTM F3187-16 standard guide for DED of metals

DED is an AM process in which focused thermal energy is used to fuse materials by melting as they are being deposited. It is used for repair, rapid prototyping, and low volume part fabrication. This document is intended to serve as a guide for defining the technology application space and limits, DED system set-up considerations, machine operation, process documentation, work practices, and available system and process monitoring technologies.

DED Systems comprise multiple categories of machines using laser beam (LB), EB, or arc plasma energy sources. Feedstock typically comprises either powder or wire. Deposition typically occurs either under inert gas (arc systems or laser) or in vacuum (EB systems). Although these are the predominant methods employed in practice, the use of other energy sources, feedstocks, and atmospheres may also fall into this category.

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3-D print battery

Ajit Behera , in Nanobatteries and Nanogenerators, 2021

2.2 Directed energy deposition

DED processes include laser engineering mesh formation (LENS), directional light production (DLF), direct metal deposition (DMD), and 3-D laser coating (LC). DED is a more complex printing process that is often used for repair or adjustment. There are components to add other materials. A typical DED machine consists of a nozzle mounted on a multiaxis arm that deposits molten material on a specific surface and solidifies on that surface. The process is basically similar to extrusion of material, but the nozzle can move in multiple directions and is not mounted on a certain axis. Materials that can be deposited from any angle with the aid of machines with four and five axes are fused during deposition with a laser or electron beam. This process can be used for polymers and ceramics but is generally used with metals in powder or wire form [30].

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Overview of additive manufacturing process

Michael Molitch-Hou , in Additive Manufacturing, 2018

4.1 Directed energy deposition

DED, also referred to as blown powder AM or laser cladding, involves the introduction of metal powder to a heat source, such as a laser, which melts the metal particles together as they are deposited (Fig. 1.12). Frank Arcella at Westinghouse Electric Corporation first filed a patent application for a powder bed-style metal 3D printing technique in 1988 [26] before developing a DED technology at Johns Hopkins University in 1997 and commercializing it through his company Aeromet [27].

Figure 1.12. In directed energy deposition, a metal feedstock is introduced to an energy source in the form of a wire (A) or as a powder (B).

At roughly the same time, a New Mexico company, Optomec, began commercializing similar technology developed out of Sandia National Labs. While Aeromet shut down its operations in 2005, Optomec continues to manufacture its laser-engineered net shaping metal 3D printers [28].

Because of the technology's ability to inject metal powder directly into the heat source, often attached to a 4- or 5-axis arm, DED systems are not limited to 3D printing onto a flat substrate. Instead, it is possible to print metal onto curved surfaces, such as existing metal structures. For this reason, laser cladding is often used to repair damaged parts, particularly for the aerospace industry.

DED machines also may not be as limited in terms of print volume. Companies such as Sciaky Incorporated have developed very large-scale systems for 3D printing of enormous metal parts to near net shape before they are machined to their final geometries (Fig 1.13). Some firms have even begun researching the ability to craft entire aircraft fuselages with DED, though the results of such work have not yet been made public.

Figure 1.13. Directed energy deposition (DED) processes involve creating a near-net shape object, that is, a part will need to be further processed (above) to reach the actual desired shape (below).

Though rough, DED is quick and capable of producing large-scale objects.

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Designing for additive manufacturing

António José Pontes , in Design and Manufacturing of Plastics Products, 2021

Directed energy deposition

Directed energy deposition (DED) covers a range of terminology ( Gibson et al., 2010): laser engineered net shaping, directed light fabrication, direct metal deposition, and 3D-laser cladding.

A typical DED machine consists of a nozzle mounted on a multiaxis appendage, which deposits the melted material onto the specified surface. The process is similar to material extrusion, but the nozzle can move in multiple directions and is not fixed to a specific axis. The material, which can be deposited from any angle due to 4 and 5 axis machines, is melted upon deposition with a laser or an electron beam (Fig. 7.9).

Fig. 7.9. Directed energy deposition process.

The process can be used with polymers, ceramics, but is typically used with metals, in the form of either powder or wire.

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Directed Energy Deposition (DED) Technology

Bhaskar Dutta , in Encyclopedia of Materials: Metals and Alloys, 2022

Introduction

Directed energy deposition (DED) technology involves using a heat source such as laser, electron beam or a gas-tungsten arc to create a melt pool and adding filler materials in powder or wire form into the melt pool. The process follows a toolpath created directly from the CAD geometry and builds up parts in successive layers. Among various metal printing technologies DED ranks second in popularity, only after Powder Bed Fusion (PBF) ( Dutta et al., 2019).

The history of metal additive manufacturing (AM) dates back to at least 1920 by Baker (US patent, 1,533,300) who used electric arc and metal electrode to form walled structures and decorative articles. Today directed energy deposition techniques such as, Direct Metal Deposition (DMD), Laser Engineered Net Shaping (LENS™) or Electron Beam Additive Manufacturing (EBAM) are based on similar ideas, but, integrates layered manufacturing concepts to create parts directly from computer-aided design (CAD) data. Patents by Dutta et al. (2019) form the basis of modern directed energy deposition (DED) technologies. More details about history of additive manufacturing and 3D printing as well as commercialization of this industry can be found elsewhere (Dutta et al., 2019). First commercial effort in directed energy deposition, started with the formation of Aeromet Corporation in 1997 which focused on a laser based directed energy deposition technology for large aerospace components made of titanium. In 1998, commercialization of Sandia National Laboratories developed LENS process by Optomec Inc. and University of Michigan developed DMD process by POM Group (now DM3D Technology) brought further thrust in to metal additive manufacturing. Due to economic reasons, early efforts on metal AM were focused on expensive parts and components, and aerospace and medical industry was a natural fit (Dutta and Sam Froes, 2016). The other popular application area of early metal AM was the tooling industry due to its low entry barrier.

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The Intersection of Design, Manufacturing, and Surface Engineering

Gary P. Halada , Clive R. Clayton , in Handbook of Environmental Degradation of Materials (Third Edition), 2018

19.4.11 Directed-Energy Deposition

Directed-energy deposition (DED) refers to a category of additive manufacturing or 3D printing techniques that involves a coaxial feed of powder or wire to an energetic source (usually a laser) to form a melted or sintered layer on a substrate. In many cases, the use of DED as a coating process is synonymous with laser cladding, although enhanced by the ability to direct the deposition to small areas. Hence, while not usually thought of as a coating process in the additive manufacturing community, in addition to being able to create free-standing 3D structures, DED can also be used to coat existing structures (Gibson et al., 2015). The added advantage of being able to direct the deposition to small areas or fine lines with a high degree of precision means that DED methods have found important applications in repair of failures (e.g., cracks) or defects (Pinkerton et al., 2015), in providing a wear-resistant coating to a particular area, or and in protecting specific areas of an object from corrosion. For example, recent reviews have discussed the ability to repair worn or corroded areas on turbine blades (Pinkerton et al., 2015). Laser_-engineered net shaping (LENS), a form of DED, has been used to create a functionally graded Co-Cr-Mo coating on porous Ti6Al4V to minimize wear while supporting excellent bone-cell interactions with the implant surface (Bandyopadhyay et al., 2009). Likewise, LENS methods were used by the same group to deposit hard Ti/TiC composite coatings on Ti metal-bearing surfaces in implants, titanium-dioxide coatings on Ti (Balla et al., 2009), Ta coatings on Ti found to promote cell growth (Balla et al., 2010), and compositionally graded yttria-stabilized zirconia coating on stainless steel to produce thermal-barrier coatings (Balla et al., 2007).

Table 19.6 provides a brief summary of the advantages and disadvantages of the coating and surface engineering technologies discussed.

Table 19.6. Advantages and Disadvantages of Some Surface Engineering Technologies

Treatment technology	Advantages	Disadvantages
Chromate-conversion coating (CCC)	• "Self-healing" corrosion protection, especially for aluminum alloys • Good adhesion for paint coatings	• Contains carcinogenic hexavalent chromium
Phosphate treatments	• Good for corrosion protection of steel • Promotes paint adhesion	• Non self-healing
Composite paint coatings	• Proven technology; easy to apply • Many formulations tailored to various design needs	• Susceptibility to UV damage; pretreatment needed to promote adhesion
Thermal-spray coatings	• Nonvacuum technique • Can coat large parts • Can create free-standing coatings • Good for a wide range of substrates • Metallic, ceramic, polymer coatings possible	• Line-of-sight coating technique • Support structure needed for large-scale deposition • Relatively thick coatings
Ion-beam implantation	• Good for forming wear, corrosion-resistant surface regions on small areas • Does not alter dimensions of part • Ion-beam mixing can be used for predeposited layers on surface	• Possible radiation damage during process; vacuum technique • Shallow penetration depth of ions
Ion beam assisted deposition	• Good for functionally graded coatings, DLC	• May need temperature control of substrate to improve coating formation, adhesion • vacuum technique
Laser ablation	• Femtosecond, UV laser ablation results in little target or substrate heating • Nanostructured coatings possible • Can use pressed pellet targets • No preferential sputtering	• Excimer ablation can result in melting • Vacuum necessary for reactive species
Chemical vapor deposition	• Nonline-of-sight • Variations enable lower substrate temperatures and control of coating thickness and morphology	• Usually requires a heated substrate and a controlled-atmosphere chamber • Can be low or high costs depending on variant chosen
Physical vapor deposition (PVD)Surface plasma treatment	• Most variants well understood • Can control phases, morphology • Rapid surface functionalization possible • Can be used to clean, etch, and remove low molecular weight or weakly bound species as well as control functionality • Relatively simple technique	• Line-of-sight • Usually requires a vacuum system • Preferential sputtering from multielement targets a problem • Often expensive solid or sintered targets • Line of sight • Multiple chemical reactions occurring in plasma can generate nondesireable functional groups • Aging can result in oxidation, hydrolysis, contamination, and surface adaptation resulting in a loss of functionality.
Functionally graded nanostructured coatings	• A variety of coatings with tailorable performance characteristics • may use various techniques (IBAD, thermal spray, PLD, ASD) • Can be matched to substrate and design and environment conditions	• Depends on techniques used
Directed-energy deposition (DED)	• Can create precise surface structures, as well as functionally graded coatings • Similar to laser cladding methods, but deposits material only where needed, less waste	• Material limitations (some metals and alloys, though feedstock materials are increasing in variety with time) • Some substrate heating will result
	• Can be integrated with CAD models of object within the manufacturing process

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3D printing composite materials: A comprehensive review

Wendy Triadji Nugroho , ... Alokesh Pramanik , in Composite Materials, 2021

4.2.2 Directed energy deposition (DED)

Directed energy deposition (DED) directs the energy into cramped and focused areas to heat a substrate, melting the material and substrate simultaneously, which is being deposited into the melt pool of the substrate. The focused heat source used by this process is commonly an electron or laser beam. Every route of the DED head forms a track from solidified materials, and the layers can be created by the contiguous material lines. A multiaxis deposition head or support material is required for the complex 3-D geometry [20]. In this process, the inert gas is supplied to deliver the powders to the substrate and shield the deposit from oxidation. A schematic representation of the DED process can be seen in Fig. 4.5.

Fig. 4.5. Schematic representation of directed energy deposition process.

DED builds the parts in a layer-by-layer manner like other 3D printing techniques. In this technique, two- or three-axis systems have a static base plate so that the nozzle moves up when each layer is deposited. For the four-axis or five-axis systems, nozzle and base are run at the same time and remain independent of each other [21]. It also allows for building more complex geometries. This process does not necessarily require a flat starting surface so that DED suits to append new material to the existing components. This new material can also be deposited on damaged parts for repairing purposes. In general, the components fabricated are in a near-net shape form and demand a final machining step.

DED technique can process the feedstock materials in the form of powder and wire with their own superiority and limitations, respectively. The powders are multipurpose feedstock in which most ceramic as well as metal materials are available in powder form. Besides, the powder form permits changing the orientation between layers to be performed easily because the attendance of excess powder flow provides the dynamic leveling on the melt pool and deposit thickness at every area of the deposited layer. Yet, not all powders can be captured in the melt pool so that the excess powders are required. Should recycling is desired, the excess powders must be recaptured in a clean condition but is not always easy to be performed.

The advantage of wire form is that the feedstock capture efficiency is almost 100% since the deposit volume is nearly similar to the amount of feeder wire [12]. The wire is suitable for simple geometries, block geometries without many transitions, both thin and thick, or with a surface coating. For the complex, large, and dense model, process parameters such as layer thickness, wire diameter, and the wire feed rate should be controlled carefully to obtain a proper deposit size and shape.

Information related to four DED machines, consisting of μPrinter [28], FormAlloy L-Series [29], LENS CS 150 [30], and LENS MTS 500 [30], are provided in Table 4.2. Those three types of DED machines originated from three manufacturers such as Additec, FormAlloy, and Optomec.

Table 4.2. DED machines and their specifications.

Variable	μPrinter	Formalloy L-Series	LENS CS 150	LENS MTS 500
Price (US$)	90,000	250,000	400,000-500,000	450,000-1000,000
Build volume (mm)	160   ×   120   ×   450	200   ×   200   ×   200	150   ×   150   ×   150	350   ×   325   ×   500
Laser power (W)	600	Up to 8000	400	500–2000
Accuracy (mm)	9	0.5–8	0.014	0.005
Printable material	Metals (any weldable materials)	Metal (nickel, iron, titanium, cobalt, copper)	Metal (stainless steel, Inconel)	Metal (stainless steel, Inconel, tungsten carbide, Stellite, Hastelloy, tool steel)

The μPrinter from Additec is the cheapest machine compared to other printers, as demonstrated in Table 4.2. This machine is capable of depositing wires and powders into complex geometries with the laser power consumption of only 600   W, but undeniably it has a small build volume and lowest accuracy [28]. FormAlloy L-Series can yield an auto-set layer thickness and autocorrect errors to produce a part free of dimensional defects. It possesses higher accuracy than μPrinter but lower than Optomec machines. Two types of DED printers, namely LENS CS 150 and LENS MTS 500, are presented in Table 4.2. LENS CS 150 may be applied for rapid manufacturing, rapid prototyping, hybrid manufacturing, and repairing. Even though it has the smallest build volume, it offers much higher accuracy as opposed to μPrinter and L-Series. As indicated by the price, LENS MTS 500 yields bigger build volume and higher accuracy than other machines. This machine applies a hybrid additive and subtractive metal processing that consists of the combination of computer numerical control (CNC) and laser engineered net shaping (LENS) technologies. Therefore, it may produce desired parts with high accuracy and good surface finish.

In general, DED printers are categorized as the high-cost machines by using laser technology and powdered metals or ceramics or composites to fabricate the objects. However, these machines can conduct rapid prototyping, manufacturing, repairing, and remanufacturing of legacy parts obtained from metal materials.

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Functionally graded additive manufacturing

Eujin Pei , ... Axel Nordin , in Additive Manufacturing with Functionalized Nanomaterials, 2021

Directed energy deposition

DED is a process where thermal energy (i.e., laser, electron beam, or kinetic energy) is used to fuse the materials while being deposited layer-by-layer on a substrate. The raw materials are fed by blowing powder through multiple nozzles or in a wire form or as gas mixtures in the build chamber. It is a fusion-based process with high energy density being involved. Generally, metal, and ceramic materials are processed through this technique. Laser metal deposition and wire arc additive manufacturing are two DED processes that can fabricate metallic parts with a graded composition [3]. These methods are used to produce two-component FGM components using pure titanium and 1080 pure aluminum [40], 304   L stainless steel and Inconel 625 [41], Nickel alloy (Ni-Cr-B-Si) and 316   L Stainless Steel [42] with graded composition.

Thermodynamic computational modeling of the DED process is often used for optimizing the process parameters to produce FGAM components [41,43]. Carroll et al. adjusted the distribution of the composition of the metallic powder mixtures through a simulation technique to improve the interface properties. A similar technique was utilized to manufacture an aircraft beam with a combination of high strength TA15 (Ti-6.5Al-2Zr-1Mo-1   V) and high ductility TA2 (Grade 3 CP-Ti) [44].

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