Powder bed fusion (PBF) is a 3D printing technique where powdered material is fused point by point using an energy source, often a laser or electron beam. This method encompasses several specific printing technologies, including Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM), Selective Heat Sintering (SHS), Selective Laser Melting (SLM), and Selective Laser Sintering (SLS).
How Does Powder Bed Fusion Work
Powder Bed Fusion (PBF) technology creates objects using a high-powered laser or electron beam to fuse powdered material layer by layer. The process begins with a recoater blade or roller spreading a thin layer of powder across the build platform.
The laser or electron beam then selectively melts or sinters specific powder areas to form each layer according to the design specifications. After each layer is completed, the build platform lowers to allow for the next layer of powder. This sequence is repeated until the entire object is formed. The unmelted powder acts as a support structure during construction and is removed once the build is finished, revealing the final solid object.
Powder Bed Fusion (PBF0 is known for its precision and ability to produce intricate and detailed components, making it ideal for manufacturing complex designs.
Types of Powder Bed Fusion
Selective laser sintering (SLS)
Selective laser sintering (SLS) is a 3D printing technique used for creating objects from polymer powders, predominantly thermoplastics, though thermosets are also becoming available. In this process, a thin layer of powder is spread across a build platform. A laser beam then selectively melts the powder according to the object's design. After each layer is fused, the build platform lowers, and a new layer of powder is applied. This cycle continues until the entire object is printed. The surrounding powder supports the part during printing, eliminating the need for additional support structures. Unused powder can often be sieved and reused, sometimes in combination with fresh material.
Selective Laser Melting (SLM)
Selective Laser Melting (SLM) operates similarly to Selective Laser Sintering (SLS) in appearance but achieves complete fusion when heating metal powder, primarily utilized for printing metal components. Like SLS, SLM selectively melts specific areas within a thin layer of metal powder, gradually building up layers atop one another. SLM operations necessitate an inert environment, typically filled with argon gas, to prevent oxidation or nitridation of the metal powder. This ensures that the powder bed remains sealed within an airtight chamber. SLM serves purposes ranging from prototyping to manufacturing full-scale components and bears resemblance to Direct Metal Laser Sintering in various aspects.
Electron Beam Melting (EBM)
Electron Beam Melting (EBM) employs a high-energy electron beam to fuse powder on the build platform. Like Selective Laser Melting (SLM), EBM uses a layer-by-layer method akin to other Powder Bed Fusion (PBF) techniques. However, EBM necessitates a fully vacuum-sealed powder chamber for optimal operation. Although it only works with a limited range of metal powders like titanium alloys and cobalt chrome, EBM produces highly dense models. These models exhibit fewer residual stresses and defects like SLM parts, but they require more extensive post-processing to achieve the desired surface finish.
Direct Metal Laser Sintering (DMLS)
Direct Metal Laser Sintering (DMLS) shares foundational principles with Selective Laser Sintering (SLS) and Selective Laser Melting (SLM), but stands out due to its extensive material versatility. Unlike SLM, which necessitates metals to achieve a full melt, DMLS operates at lower temperatures, making it compatible with a broader range of metal alloys. In DMLS, metal powder is selectively fused rather than fully melted, allowing for the creation of complex geometries with high precision. The process starts with a thin layer of metal alloy powder being deposited onto a build platform by a roller or re-coater. A laser then selectively sinters this powder layer by layer to form the desired shape. Like SLM, DMLS is conducted in an inert gas environment to prevent oxidation and maintain optimal printing conditions.
Selective Heat Sintering (SHS)
Selective Heat Sintering (SHS) is an additive manufacturing process similar to Selective Laser Sintering (SLS) but with a key difference in the heat source used. SHS employs a thermal print head to sinter thermoplastic powder, whereas SLS utilizes a laser to achieve the same effect. Despite their similarities, it is important to distinguish between these two methods due to their differing mechanisms.
Post-Processing for Powder Bed Fusion
Plastic Powder Bed Fusion parts are extracted from the bed of unfused powder any excess material is cleaned using a bead blast. This method also ensures a uniform surface finish. In our standard finishing process, Multi Jet Fusion (MJF) parts receive a black dye treatment to further enhance their finish quality.
Metal Powder Bed Fusion parts require heat treatment to alleviate the internal stresses caused by the printing process. Post-heat treatment, support structures are removed, and additional post-processing steps can be undertaken. Based on customer requirements, various techniques such as CNC machining and polishing can be used to enhance the surface quality.
Comments