Direct Energy Deposition (DED): Definition, Examples, How Does It Work, Advantages and Disadvantages
Direct energy deposition (DED), also referred to as directed energy deposition, is a particular approach to additive manufacturing (3D printing). It directs an energy source at a spot on the source material to make a small amount of melt and then adds feed material to this melt in order to deposit new material onto the component. Details about the available DED energy sources, different feed systems, and advantages and disadvantages will be explained below.
Direct (or directed) energy deposition (DED) is a method of additive manufacturing (3D printing). An energy source is directed onto a point and feed material is introduced to the same spot so it can be deposited onto the workpiece. It has some similarities to robotic welding in which a metal wire is melted (deposited) onto the main component. DED devices may use electron beams, lasers, or electric arcs to form the melt pool. New material can come in the form of wire filament or powder. Figure 1 is an illustration of DED:
Schematics of Two DED Systems.
Image Credit: https://www.sciencedirect.com/
Direct energy deposition works by heating a specific area on the manufactured component to melting temperature and then adding feed material. The print head moves along the build path, and the melt then solidifies with the feed material having been deposited onto the main body.
The directed energy source (either a laser, electron beam, or electric arc) sits in the center of a print head, with the feed material adjacent to it. The feed material can be supplied in the form of a wire filament or a powder. The filament gets fed at an angle so that it melts at the energy source’s focal point. Powder, on the other hand, is transported by an inert gas through nozzles arranged concentrically about the energy source, and directed at the melting point.
The print head has multiple planes of movement. It can either be mounted to a multi-axis CNC head or an articulated robotic arm. For more information, see our guide on Types of Additive Manufacturing.
There are a number of advantages to using DED technology:
- Relatively Large Build Volumes: Because the print head of a DED machine is usually mounted on a multi-axis CNC head or an articulated arm, it can cover a fairly large area compared to other 3D printing methods (particularly those that work with metal). Prints can exceed one meter cubed.
- Multiple Materials: Many feed materials are compatible with DED fabrication. They can be introduced either through a powder blend or multiple filament feeds. In fact, the material composition can be changed during the build.
- Less Material Waste: Compared to powder-bed fusion, less excess feed material needs to be applied in order to complete the print.
- Control of the Grain Structure: DED allows some control of the grain structure of the deposited material. By adjusting the speed of the print head, you can control the cooling time.
- Can be Used to Repair: DED is not limited to creating new parts from scratch like most 3D printing processes. The machines can deposit material directly onto an existing part as well. This means that DED can be used to repair damaged or worn components.
DED is not the ideal solution for every case, as the technology does have some disadvantages:
- Low Resolution: Generally, DED technology is only capable of creating features at a low detail resolution. This is a function of the feed wire thickness and the size of the melt pool. The resolution also depends on printing speed — faster printing will result in a lower resolution.
- High Capital Cost: DED devices are expensive. Most need complex systems such as a hermetically sealed printing chamber, vacuum or inert gas system, a powder room for systems with powder feed, etc. They’re a relatively new technology, so they haven’t yet received many cost-cutting refinements.
- Post-processing: Parts manufactured with DED technology usually require post-processing to achieve nice surface finishes. This usually comes in the form of some light machining and polishing in order to remove excess deposition and create a smooth, consistent surface.
DED is able to print with varied materials. The majority of materials used with DED technologies are metals such as: titanium and titanium alloys, Inconel®, tantalum, tungsten, and some stainless steel varieties.
Certain nonmetals also function on DED machines — a type of carbon fiber can be printed in which a carbon filament is laid into a thermoplastic polymer. Alumina and zirconia ceramics also work well with DED.
Additive manufacturing with metals and other materials gives DED the ability to fit many applications, some of which are not options for other 3D printing methods:
- Repairing Existing Parts: The primary purpose of DED technology is in the repair of metallic parts. The method can deposit new material on complex surfaces. With adjustments to the speed and energy source, it is also possible to control the grain structure of the deposited material to match that of the original part. DED is therefore used to repair expensive components such as turbine blades.
- Near Net Shape: DED can manufacture parts that are very close to their planned dimensions. This is very valuable when manufacturing exotic and expensive materials or materials that are very difficult to cut and machine.
- Composite or Hybrid Parts: DED gives you the ability to print with different materials at the same time. A blend of compatible materials can go into the printed item, and its composition can even vary throughout the print.
The print quality of DED is crucial to the finished products’ usefulness. The following factors have an influence on quality:
- Porosity: Porosity in the deposited material results in weak points — the pores are essentially internal defects. Porosity should be minimized by drying the powder feed to keep moisture out and by the proper use of shielding gas.
- Scan Speed: The speed at which the head moves along the build path affects the size of the melt pool, the cooling rate, and therefore the grain structure. Taken together, it all impacts the part’s quality. The optimum speed will depend on the material used and the desired grain structure.
- Power: The power provided by the energy source has a direct effect on the melt and is related to the scan speed. Energy transfer to the component must be sufficient to properly melt the host material even as the DED print head moves along the build path. If it doesn’t put out enough power, the print quality will not be up to snuff.
DED technology is complex and challenging to implement.
- High Capital Costs: One of the major barriers to implementing DED technology is the large initial investment necessary to set it up.
- Lack of Skilled Technicians: Skilled and experienced operators are necessary to run the DED system efficiently and accurately. Since this is a growing field, skilled technicians are hard to come by. You may choose to train your personnel in-house rather than hire new people, but this still is neither quick nor cheap.
- New Design Approach: When designing components to be built using DED technology, you must always consider how the print head moves. If they’re not designed for it from the outset many parts will need some redesign before being manufactured with DED. This process adds effort and work hours each time.
- Absence of Standards: Additive manufacturing, in general, is still a relatively new technology and new technological approaches are being developed each year. There is little standardization in digital information management, design, or manufacturing processes for these systems.
The decision of which DED device to buy requires a fair amount of research and consideration. There are a number of key aspects to investigate when choosing DED equipment:
- Material Compatibility: The most important part of the decision is what materials you expect your equipment to print. A machine that can print ceramics will differ significantly from one that is only intended for metals.
- Build volume: Another key consideration is the largest component you expect to manufacture. This will dictate your DED equipment’s overall build volume.
- Precision: Depending on the type of components and the post-processing you’re planning, you may have to choose equipment based on its precision. You may be forced to weigh the trade-offs between a larger, faster machine and one with better precision.
DED is able to build a component much closer to its final shape (near net shape) than most standard manufacturing options. It thus uses far less material to achieve the finished item. Traditional manufacturing methods require a block of source material that is then carved using subtractive manufacturing methods. They remove material in order to arrive at the final part. This removal of material generates a lot of material waste as cuttings and shavings. Therefore, DED is more efficient than traditional methods in terms of material usage.
DED processes can also generate more complex parts thanks to the multi-axis movement of the print head and the nature of building a component progressively, one layer at a time. Traditionally manufactured items are more limited in terms of geometry. Ordinarily, complex parts must be built as a series of smaller parts to be assembled after the fact.
The environmental impacts of additive manufacturing as a whole are still under investigation. The most common environmental concern with additive manufacturing technologies, DED included, is their high energy demand. The choice of the most efficient manufacturing process (between typical, subtractive methods and newer additive processes) depends on the complexity and volume of the parts to be manufactured.
There are currently three different variations of DED technology. They’re categorized according to the energy source used to melt the feed material:
An electric arc is created between the print head and the workpiece. Wire arc additive manufacturing (WAAM) is one of the primary arc-based methods.
An optical laser is used as the energy source in this variation, also referred to as laser engineering net shaping (LENS). Net-shape manufacturing means that the original manufactured part is very close to the finished (net) dimensions. With LENS, the material deposition needs to occur in an inert environment to prevent oxidation, which either means the manufacturing chamber must be fully purged with inert gas or a feed of shield gas must constantly flow as a shroud around the deposition point.
An electron beam is used to provide the energy to melt the feed in the approach known as electron beam additive manufacturing (EBAM). This DED process must occur in a vacuum to prevent the electrons from interacting with air molecules.
Each DED device delivers material to the part’s surface using one of two feed methods:
With a powder feed, the nozzle that provides the energy source also contains material feed nozzles arranged concentrically about it that direct powder at the deposition point. Inert gas flow is used to deliver the powder, and the inert gas further acts to inhibit oxidation or other chemical reactions between the molten materials and the surroundings.
Wire-based DED is similar to welding in that the feed material is provided as a wire filament. This wire is fed at an angle from beside the energy source and at a constant rate dictated by the rate of deposition.
DED costs are similar to those of other approaches to additive manufacturing with metal. However, metal 3D printing is substantially more expensive than simpler technologies that are only made to print polymers. In terms of capital cost for the equipment, a DED system will fall in the range of $500,000. This is comparable to the average cost of a selective laser sintering (SLS) system, although the details will depend on the specifications and quality of each machine. Generally, metal 3D printing machines are not sold for less than $400,000.
The per-part manufacturing costs will vary significantly depending on the size and complexity of the part and the print material. However, the cost will likely be in the range of $5,000-10,000 per part, taking into account the cost of the material, heat treatment, stress relief if necessary, and final machining. With systems that use powdered feed, the cost of producing the powdered metal is significant, adding to the raw material cost. For more information, see our guide on Inconel.
Yes, DED works with Inconel®. Inconel is a family of nickel-chrome alloys with superior corrosion resistance. They’re well-suited to extreme environments. DED has been successfully used to repair Inconel components, and further investigation and development are ongoing.
Yes, DED can function with nonmetals, although the range is limited. DED can be used to manufacture 3D-printed parts with carbon fiber, as well as some polymers and ceramics.
No, DED does not require support material. The print head of a DED machine is usually mounted on either a multi-axis CNC head or an articulated arm and therefore is able to access the workpiece from multiple angles. This means that supports are not necessary, as deposition can occur directly onto almost any of the model’s surfaces.
The difference between directed energy deposition (DED) and powder bed fusion is the mechanism by which new powder is supplied for addition to the main piece. A powder bed fusion machine will fill and spread powder from a feed bed into the build bed. After one layer of the printed model is fused, the floor of the build bed lowers slightly to lower the model, and new powder is added and smoothed over by a roller. In this way, the manufactured model is fully submerged within feed powder, and a great deal of excess powder is needed.
With DED 3D printing, the manufactured model is stationary. Energy is directed at a specific point on the model, and feed powder is supplied to that point, to be melted and deposited on the larger model. Less feed powder is required for this process than in the powder-bed-based method. For more information, see our guide on Powder Bed Fusion (PBF) machines.
This article presented direct energy deposition, explained what it is, and discussed how it works and its advantages and disadvantages. To learn more about direct energy deposition, contact a Xometry representative.
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