Key advantages of powder bed fusion

Additive metal manufacturing consists of a wide range of technologies and techniques. One of the most mature technologies is powder bed fusion (PBF). Invented in the 1980s, it has had decades to improve and as such still stands out as one of the most efficient metal printing processes. This article will explore the benefits of PBF.

What is powder bed fusion?

Powder bed fusion is a blanket term used to describe a range of technologies that fuse metal powders together using a beam of energy. Below are some of the terms used to describe various powder bed fusion techniques.

• Selective Laser Melting (SLM) – SLM refers to the trademarked process that uses a laser system to fully melt metal powder.
• Direct Metal Laser Sintering (DMLS) – DMLS is another trademarked process similar to SLM. Despite the word sintering, the powder is in fact completely melted.
• Electron Beam Melting (EBM) – EBM is similar to SLM but uses an electron beam in an inert atmosphere or vacuum chamber. The beam also melts the particles together like SLM.
• Selective Laser Sintering (SLS) – This process typically refers to powdered polymer materials as the laser only sinters the particles together and does not fully melt the material.

Despite the subtle differences, these technologies all have the same working principle.

How does it work?

The typical powder bed fusion process starts with powder being loaded into a reservoir in the machine. A first layer of powder is deposited onto the print bed. This layer’s thickness is equal to the Z-axis layer resolution in the final part. A laser then traces out the cross section of the part and as it does so, the metal powder particles melt and fuse to each other to create a solid part. Once the first trace is done, the print bed moves down. Another layer of powder is laid over the previous one and the process begins again. This time the metal particles fuse to the layer below as well as to their neighbours. This process continues until the entire part is built up. During printing, the print volume is filled with an inert gas to improve print quality by displacing any reactive impurities from the air that may cause a loss of part quality. After the print is done the part is removed from the machine and excess powder is collected for recycling. Any support material is also removed after cleaning. 

Advantages of powder bed fusion

Powder bed fusion offers a wide range of advantages, some of which are listed below.

• Reduced material waste – Building up the part layer by layer eliminates most of the waste associated with subtractive manufacturing technologies. After the part is complete, any excess powder is collected and recycled.

• Improved manufacturing times – PBF techniques are often considered slow when compared to other technologies. However, when it comes to complex parts with intricate internal geometry, no other technology can compare. A complete part can be designed, manufactured, tested, re-designed and printed again in less time than it takes other technologies like metal casting or MIM to produce the same complex part.

• Flexibility – Flexibility is the key to innovative product development. The option to quickly iterate on a design means that if a part has a weak spot or a flaw in the design, it can be updated in CAD and then be re-printed and put back into testing or production.

• Material range – PBF works with a wide range of materials like titanium, tool steel, inconel, aluminium, stainless steel, and various others. Any material that can be turned into a powder using a gas or plasma atomisation process can be used.

• Support structures – PBF parts require limited support structures during printing. This is due to the unused powder acting as support. This also means that complex internal structures can be created. Examples include the cooling channels inside turbine blades; excess powder can simply be poured out of these internal volumes.

Typical products

Due to the flexibility of powder bed fusion metal manufacturing, it has been adopted by a wide variety of industries. Some examples are listed below.

Aerospace

The aerospace industry makes use of PBF to manufacture production parts. These can include turbine blades, fuel nozzles, and guide vanes to name a few. PBF allows for efficient production of critical aerospace components that minimise weight.

Medical Implants

Medical implants are an ideal application for PBF. These implants are often built with advanced bio-compatible materials and need to be manufactured with complex surface structures to allow tissue to anchor to them. Artificial hip joints are a common example.

Automotive

Within the automotive industry, PBF is used primarily for prototyping. However, metal components like brake pads with cooling ducts are manufactured for motorsports applications where the cost of limited production is justified.

In conclusion

Powder bed fusion is one of the most mature metal additive systems and as such, this technology offers the advantage of decades of industry experience. Whether you are designing a new component and need to iterate on designs rapidly or are looking for a more efficient process to manufacture advanced components, PBF can meet your needs. To find out more, contact the Kingsbury team today.

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