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Powder Vs Wire – A Guide to Metal Additive Manufacturing by Digital Alloys

Metal additive manufacturing technology
ABOUT THE AUTHOR
Metal additive manufacturing technology
Above: Powder Vs Wire metal additive manufacturing feedstock/Image Credit: Digital Alloys

The type of feedstock used in a metal additive manufacturing (AM) process can greatly influence material cost, print speed and resolution, quality, and safety. Powder or wire is the primary input material in >90% of commercial metal AM processes. This post highlights the most significant pros and cons of these two feedstocks. We will compare how these two feedstocks affect:

  • Material Cost
  • Print speed and resolution
  • Quality
  • Safety
Metal additive manufacturing technology
Above: Metal additive manufacturing technology landscape/Image Credit: AM Power

Material Cost

In production manufacturing, raw materials are one of the largest cost drivers. In Metal AM, raw materials include the primary feedstock (print material) and any secondary process materials like the binders used in Binder Jetting. Although secondary materials can be expensive, relatively small amounts are used and not much cost data has been published. We will not consider secondary materials in this post.

Metal costs vary significantly across 3D printing processes. Titanium, a popular metal AM material, is an example. PBF processes require small and highly spherical powders which are expensive to produce – Titanium powder is $300-$500/kg for PBF. E beam PBF, powder DED, and Binder Jetting processes are able to utilize lower quality powders manufactured for the metal injection molding (MIM) industry. These MIM Titanium powders are in the range of $150-$250/kg. Wire is the most affordable (and abundant) option since it manufactured more efficiently than powder and is consumed in high volumes by the welding industry. Wire-based AM systems use titanium that typically costs $125-175/kg.

Note: Some equipment manufacturers require that you purchase “sole-source” material from them at huge margins. Others have “open” material systems that allow you to purchase from 3rd party material vendors at much lower costs. This is a significant factor in material pricing.

Material waste must be considered when determining total material costs. Waste includes material used in any near-net-shape expansion and support structures that are later removed from the part.  Another waste stream is unprinted powder in powder-bed builds that can be difficult to reuse. As an example of this, aerospace manufacturers with high quality requirements may only be able to reuse 50% of the un-sintered powder in a PBF build.

Wire-based processes typically have more waste in near-net-expansion and support structures than power-based processes. Powder-based processes use a higher cost material and suffer from powder reuse limits.  Wire-based systems generally have lower overall material costs. Approximate total material costs for a typical 1 kg (final weight) Titanium part are shown below:

Metal additive manufacturing technology
Above: Total material costs for a typical 1 kg (final weight) Titanium part/Image Credit: Digital Alloys

Our post on the Economics of Metal AM goes into more detail on material costs as well as the other major cost drivers.

Print Speed and Resolution

Compared to wire-based systems, powder-based processes deliver higher resolutions but much lower print speeds. The exception is Binder Jetting, which claims impressive print speeds but requires long, expensive de-binding and sintering steps which negate the speed advantages for the complete manufacturing process. Power bed processes often also require additional slow, expensive post-processing steps like HIP-ing to improve material properties and reduce porosity in printed parts.

Wire based processes, while lower resolution, can print at much faster rates. The below chart highlights the deposition rates possible in DED processes as a function of resolution (deposition width, which is correlated to wire feedstock diameter).

Metal additive manufacturing technology
Above: DED Print Speed vs Resolution/Image Credit: Digital Alloys

Wire-based DED processes can print at up to 10 kg/hr using thick wire (>3mm) and relatively low resolution (>15mm deposition width). Joule Printing™ can achieve similar speeds but with much smaller wire (<1mm). This results in an order of magnitude higher resolution at similar print speeds.

Quality and Safety

Wire has quality and safety advantages over metal powder. Due to high surface area, metal powders are especially sensitive to their environment. This makes metal powders prone to absorb moisture, oxygen and other elements present in the air, affecting printability and the final material properties of the part. Metal powder is also a safety risk due to its potential for flammability and inhalation. Manufacturers who choose to bring metal powders into their facilities must build and maintain expensive infrastructure, safety equipment, and careful procedures to manage these risks. Below you can see the typical suit, gloves, and masks required to handle powder. These precautions are not necessary for wire processes.

Metal additive manufacturing technology
Above: Operator gathers powder from the PBF build chamber/Image Credit: Machine Design

Conclusion

Powder-based printing (PBF & Binder Jetting) is challenged by safety, high material costs, limits with powder re-usability, and additional post-processing steps. However, there are many applications that require higher resolutions than are possible with wire-based printing. Powder-based printing remains the best solution for small, complex parts with fine internal features, but these designs must create enough business value to justify the associated process risks and costs. 

Wire-based AM processes (wire DED & Joule Printing) are simpler, faster, safer, and lower cost than those using powder. While wire-based printing sacrifices resolution in achieving these advantages, the net production benefits are clear. For larger, near-net-shape applications where wire-based processes can meet requirements, it is almost always the better solution.

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