7 Types of Metal Additive Manufacturing Processes

Additive manufacturing, also known as 3D printing, is an industrial process used to make parts. On the basis of digital 3D data control, the desired shape is printed layer by layer by depositing materials. Typically, powders of a variety of materials are used for construction, including metals, ceramics, plastics, and composites. Metal AM is the advanced approach to produce high performance metal parts in wide range of industries. In this article we will introduce the common 7 types of metal AM processes in additive manufacturing industry.

SLM ( Selective Laser Melting )

In Selective Laser Melting, or SLM for short, also know as DMLS. The metal powders are firstly put on a powder bed and then locally melted by a high energy laser. The substrate of the powder bed will be then goes down layer by layer after each layer has been printed, which will be repeated until the part is complete. SLM printing allows for the manufacturing of components with unusually high densities of over 99.5%, smooth surfaces, and great strength. For instance, a honeycomb structure can be created by fabricating individual layers with lower densities. The printed part can either be used straight away or further processed to produce a superior surface quality, such as heat treating, polishing, etc. A range of industrial applications, including prototyping, mold-making, and the molding of medical products, use SLM printing.

EBM ( Electron Beam Melting )

EBM works in a way similar to selective laser melting, except that the energy comes from the EBM energy from the electron beam, while the SLM comes from the laser energy. EBM 3D printers all include an energy source that emits an electron beam, a powder container, a powder feeder, a powder coater, and a heated build platform. 3D printing itself starts with a powder coater, which deposits a layer of preheated powder onto a build platform. Once the powder solidifies, electron beam melting begins. The electron beam is controlled by a set of electromagnetic coils that precisely direct the beam to the desired point on the build platform. The electron beam moves selectively as it melts the powder, causing the powder particles to fuse together. After completing a layer, the build platform moves down the height of one layer. The coater comes in again with a new layer of powder, and the electron beam begins to induce fusion of the powder particles, resulting in the formation of a new layer... Repeat this process until the entire part is complete.

WAAM ( Wire Arc Additive Manufacturing )

WAAM, or Wire Arc Additive Manufacturing, is based on electric arc welding and in some ways appears to address the weaknesses of powder bed-based additive manufacturing processes. Instead, wire is used here, which is easier to store and involves fewer safety risks in its processing than metal powder. The WAAM process can be used to create near-contoured blanks, however, these blanks are difficult to illuminate precisely and almost always require post-processing. While high-alloy steels, titanium and stainless steel can be machined without problems, the method is only suitable for machining copper alloys to a limited extent - pure copper is not possible. Since the manufacturing process does not require any lasers, the entire process can be safely monitored and documented.

BJ ( Binder Jetting )

In binder jetting, metal powder is used, which is not melted but bonded. After the powder layer is applied, it is bonded with adhesive where it belongs to the components. The printer works like a traditional inkjet printer. There is no ink in the printhead, but adhesive. Materials that can be used as adhesives include synthetic resins, but water-based adhesives are also common. No additional support elements are required as the surrounding powder supports the assembly during the process. After the manufacturing process, the binder must be removed and the assembly sintered. This is the only way to get a fairly solid workpiece. However, post-processing steps produce varying degrees of shrinkage, so experience is required to produce satisfactory BJ parts. Compared to other methods proposed, binder jetting is a rather old process, dating back to the 1990s.

LENS ( Laser Engineered Net Shaping )

The metal nozzle of LENS moves according to the preset path. At the same time, the powder nozzle directly transports the metal powder to the molten pool formed by the laser spot on the solid substrate, so that it solidifies in the sequence from point to line and from line to surface, so as to Complete the print job of a layer section. This builds up layer by layer to create a near-net-shape component entity. What is special about this manufacturing process is that it can be used to produce particularly large parts.

FDM ( Fused Deposition Modeling )

Fused Deposition Modeling, commonly referred to as the molten layer process, works as follows: Liquid metal powder is pressed through a fine nozzle and layered in thin lines. At the same time, the support structure is made of a second material, which can be removed later. As for post-processing, sintering is required to obtain an all-metal structure. Among other things, FDM methods are used in aerospace and medical technology as well as in the automotive industry.

NPJ ( Nanoparticle Jetting )

Nanoparticle Jetting was developed by the Israeli company XJet and is based on inkjet technology. In extremely fine layers, tiny particles mixed with a binder are applied to a build platform that has been heated to nearly 300°C. After completion, the support structure can be rinsed in a special liquid - done. This completely new process is currently being further developed, with a focus on metal printing. In the future, aviation and medical technology will be the main customers.