Nowadays, with the rapid development of technology, metal 3D printing technology, which has the advantages of short-term manufacturing, on-demand manufacturing, and rapid prototyping, is making many impossibilities possible.
There are currently five mainstream metal 3D printing technologies in the market: laser selective sintering (SLS), nanoparticle spray metal forming (NPJ), laser selective melting (SLM), laser near net shape (LENS), and electron beam selective melting (EBSM). Next, let me introduce the basic working principles of these five metal 3D printing technologies.

　01. SLS laser selective sintering
Working principle: A layer of powder material is pre laid on the workbench, and the laser is controlled by the computer to sinter the solid part of the powder according to the interface contour information. Then, it is continuously cycled and stacked layer by layer to form the solid part.
The SLS method uses infrared lasers as energy sources, and the modeling materials used are mostly powder materials. When processing, first preheat the powder to a temperature slightly lower than its melting point, and then flatten the powder under the action of a scraper; The laser beam is selectively sintered under computer control based on the layered cross-sectional information. After one layer is completed, the next layer is sintered, and this process is repeated layer by layer until the three-dimensional part is formed, Retrieve the unsintered powder into the powder cylinder and remove the molded parts.
Due to its simple manufacturing process, high flexibility, wide range of material selection, low material price, low cost, high material utilization rate, and fast forming speed, this molding method is mainly used in the casting industry and can be directly used to produce rapid molds.
02. NPJ Nanoparticle Spray Metal Forming
Working principle: First, metal is loaded into a 3D printer in liquid form, and during printing, a liquid containing metal nanoparticles is sprayed into shape. Then, the excess liquid is evaporated by heating, leaving behind a metallic portion, which is then formed by low-temperature sintering.
This molding method can use ordinary inkjet print heads as tools and can melt and remove support structures through specialized techniques without the need for any external force. Because it is removed by melting, theoretically it can be infinitely added, giving designers greater freedom. In addition to metal materials, its breakthroughs in ceramic technology have expanded its applications to dental, medical, and specific industrial fields.
03. SLM laser selective melting
Working principle: Using a high-energy laser beam to melt the metal alloy powder on the two-dimensional cross-section of the sliced 3D model, and printing any complex structure and metal parts with near 100% density layer by layer from bottom to top.
SLM technology mainly utilizes CAD 3D software to design 3D models and export them in a file format that slicing software can recognize; Slice the 3D model and add support and layering to obtain the cross-sectional profile data of the 3D model; Using path planning software to scan and process contour data, the path planned data is imported into SLM equipment. The industrial computer controls the laser beam selection to melt metal alloy powder layer by layer according to the scanning path of each contour layer, and stacks them layer by layer to form a dense three-dimensional metal part entity.
The advantage of SLM technology lies in its high material utilization rate, high dimensional accuracy of the manufactured metal parts, and the ability to design freely. Its limitations lie in the high cost of equipment components, inability to achieve mass production of products, and inconsistent standards for metal alloy powder required for processing. Therefore, SLM is mainly used in aerospace, biomedicine and other fields, suitable for the manufacturing of valuable and difficult to process metal components such as titanium alloys and nickel alloys.
04. LENS laser near net shaping
Working principle: The computer slices the three-dimensional CAD model of the part into layers to obtain the two-dimensional planar contour data of the part, and converts the contour data into the motion trajectory of the CNC worktable. At the same time, metal powder is fed into the laser focusing area at a certain powder supply speed, rapidly melted and solidified, and formed into three-dimensional nearly net shaped metal parts through layer by layer stacking of points, lines, and surfaces.
LENS can achieve mold free manufacturing of metal parts, resulting in parts with dense structure, obvious rapid melting characteristics, high mechanical properties, and the ability to manufacture heterogeneous and gradient material parts as well as high-strength metal parts such as titanium alloys.
05. EBDM electron beam selective melting
Working principle: First, slice and layer the 3D CAD model of the part, and input the obtained discrete data into the forming system. Preheating treatment is carried out in the forming system, and then the electron beam melts the powder pre laid on the worktable according to the CAD data of the part. After one layer is processed, the worktable descends by one layer thickness, and then the next layer of powder is laid and melted. At the same time, the newly melted layer is fused with the previous layer. Repeat this process layer by layer, directly forming and manufacturing three-dimensional parts.
EBDM technology has advantages such as fast processing speed, high energy utilization rate, low vacuum pollution, low residual stress in components, and no reflection. It is particularly suitable for direct molding of active, refractory, and brittle metal materials, and has broad prospects in fields such as aerospace, biomedical automotive molds, etc.