A set of diagrams to understand metal 3D printing technology

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With the rapid development of 3D printing technology in recent years, it is rapidly changing the way we traditionally produce and live. As a typical representative of the emerging manufacturing technology, metal 3D printing technology, which was earlier applied in the aerospace field, has shifted more to the industrial, automotive, medical, mould and die, education and jewellery markets. How much do you know about the technology Today I would like to explain the mainstream metal 3D printing technology.

There are now five mainstream metal 3D printing technologies: laser-selective sintering (SLS), nanoparticle jet metal forming (NPJ), laser-selective melting (SLM), laser near net forming (LENS) and electron beam selective melting (EBSM) technologies.

Selective Laser Sintering (SLS)
The entire SLS process unit consists of a powder cylinder and a forming cylinder. The powder cylinder piston rises and a powder laying carriage spreads a uniform layer of powder over the forming cylinder, while a computer controls the 2D scanning trajectory of the laser beam to selectively sinter the solid powder material to form a layer of the part based on a slice model of the prototype. After a layer is completed, the working piston drops one layer thickness and the powder laying system lays down a new layer, controlling the laser beam to scan and sinter the new layer again. This cycle is repeated, layer by layer, until the three-dimensional part is formed.

The laser-selective sintering process:

SLS part model layered slicing
Laser-selected sintering
SLS moulded part removal
Post-processing of SLS moulded parts

Nanoparticle Jet Metalforming (NPJ)
While it is well known that ordinary metal 3D printing technology uses laser melting or laser sintering of metal powder particles, Nanoparticle Jet Jetting (NPJ) technology uses a liquid form rather than a powder form. The metal is encased in a tube in liquid form and inserted into a 3D printer, where it is shaped by a jet of 'iron' containing metal nanoparticles during the 3D printing of the metal. The benefit is that by printing the metal in iron water, the whole model is more rounded and can be used as a tool with a normal inkjet print head. When the print is complete, the build chamber is heated to evaporate the excess liquid, leaving only the metal part behind.

Nanoparticle jet metal forming process:

Metal particle refinement
Metal particles distributed on droplets
Droplet injection moulding process
Liquid phase discharge process
Formed parts

Laser Selective Melting (SLM)
The basic principle of laser selective melting technology is to first design a 3D solid model of the part on a computer using 3D modelling software such as Pro/e, UG, CATIA, etc., and then slice and layer the 3D model through slicing software to obtain the contour data of each section, and generate filled scan paths from the contour data. The machine will follow these fill scan lines and control the laser beam to selectively melt the layers of metal powder material, gradually stacking them into a 3D metal part. Before the laser beam starts scanning, the powder laying device first pushes the metal powder onto the substrate of the forming cylinder, the laser beam then follows the filling scan line of the current layer, selectively melting the powder on the substrate and processing the current layer, then the forming cylinder drops a layer thickness distance, the powder cylinder rises a certain thickness distance, the powder laying device then spreads the metal powder on the current layer that has been processed, the device transfers the next layer of contour data for processing. So layer by layer until the entire part is processed.

The laser zone melting process:

SLM moulded parts
Formed parts to support
Post-processing of formed parts
Electron beam selective melting of printed parts

Laser Near Net Shaping (LENS)
Laser Near Net Structuring (LENS) technology uses the principle of simultaneous operation of laser and powder conveying. The computer slices the 3D CAD model of the part in layers and obtains the 2D planar profile data of the part, which in turn is transformed into the movement path of the CNC table. LENS enables the manufacture of metal parts without moulds, resulting in significant cost savings.

The laser near net forming process:

Laser near-net-shape coaxial powder feeding
Laser near net forming build process