☞ This is the 20593th article published by Metal Processing (mw1950pub).

Editor’s Note

3D printing is known as a “manufacturing technology with industrial revolution significance.” In recent years, with advancements in industrial technology, 3D printing technology has rapidly developed and gained widespread media attention. Are you also a bit confused by the numerous 3D printing technologies? No worries, I have compiled the top ten 3D printing technologies and vividly presented their principles through animated images.

This article shares the principles of 3D printing in the polymer and metal categories, mainly introducing five major technologies: SLA, CLIP, 3DP, PolyJet, and FDM, as well as five metal 3D printing principles: NPJ, SLM, SLS, LMD, and EBM.

1. SLA (StereoLithography)

SLA, or Stereolithography, is a light-curing molding technology that uses ultraviolet light to irradiate liquid photosensitive resin, causing a polymerization reaction to cure layer by layer and generate a three-dimensional solid. The dimensional accuracy of parts produced by SLA is high, and it is one of the earliest commercialized 3D printing technologies.

The following is the SLA process engineering.

Ultraviolet Laser Source

Light-Curing Reaction

Layered Scanning Molding

2. CLIP

CLIP, or Continuous Liquid Interface Production, is a revolutionary 3D printing technology developed by Carbon 3D based on SLA technology, increasing the speed of 3D printing by 100 times.

CLIP projects from the bottom, curing the photosensitive resin, while controlling oxygen in the uncured areas to form a dead zone that inhibits the light-curing reaction, thus ensuring the continuity of curing.

Light-Curing Reaction

Oxygen Inhibition of the Light-Curing Process

Demonstration of the Light-Curing Dead Zone

CLIP Molding Process

3. 3DP (Three-Dimensional Printing)

3DP, or Three-Dimensional Printing, is a rapid prototyping technology that is similar to traditional two-dimensional inkjet printing. It sprays a binder (colored binders can print colored parts) from the nozzle, binding the powder on the platform to form a shape, usually using gypsum powder as the molding material. Currently, 3DP technology is mainly applied in two areas: full-color 3D printing and sand mold casting.

The following is the sand mold casting process using 3DP technology by Exone.

Binder Jetting

Heating and Curing

Printing and Molding

Casting and Molding

4. PolyJet

PolyJet is a polymer jetting technology whose molding principle is similar to 3DP technology, but instead of a binder, it jets light-curable resin, which is cured after spraying using ultraviolet light.

PolyJet Molding Principle

PolyJet uses an array of nozzles and can even simultaneously jet different materials, achieving multi-material and multi-color printing.

Array Nozzle Working Process

PolyJet Printing Process

5. FDM (Fused Deposition Modeling)

FDM, or Fused Deposition Modeling, utilizes high temperatures to melt materials, extruding them through a print head into filaments that accumulate on the build platform. FDM is the simplest and most common 3D printing technology, typically used in desktop 3D printing devices.

The following is the working principle of FDM technology.

Model Processing

Material Extrusion Molding

Layered Printing Process

Support Removal

Surface Treatment

Metal 3D printing technology can be directly used for the rapid prototyping of metal parts, with broad industrial application prospects, and is a key area of development for 3D printing technology both domestically and internationally.

Next, I will share the principles of five metal 3D printing technologies: NPJ, SLM, SLS, LMD, and EBM.

1. NPJ (Nano Particle Jetting)

NPJ technology is the latest metal 3D printing technology developed by the Israeli company Xjet. Compared to conventional laser 3D printing, it uses nano liquid metal, depositing it in a jetting manner, achieving a printing speed five times faster than ordinary laser printing, with excellent precision and surface roughness.

The following is the working process of Xjet equipment.

Metal Particle Refinement

Metal Particles Distributed in Droplets

Droplet Jetting Molding Process

Liquid Phase Discharge Process

Sintered Parts

2. SLM (Selective Laser Melting)

SLM, or Selective Laser Melting, is currently the most common technology in metal 3D printing. It uses a finely focused laser beam to rapidly melt pre-placed metal powder, directly obtaining parts of any shape with complete metallurgical bonding, achieving a density of over 99%.

The laser scanning system is one of the key technologies of SLM. The following is the working diagram of the scanning system from SLM Solution.

Laser Emission

Laser Transmission

Scanning Galvo

Laser Scanning and Melting

Metal Powder Melting Process

During the metal 3D printing process, due to the complexity of the parts, support materials are usually required. After the parts are completed, the supports need to be removed, and the surface of the parts needs to be treated.

Removing the Parts

Removing Supports

Post-Processing

3. SLS (Selective Laser Sintering)

SLS, or Selective Laser Sintering, is a technology similar to SLM, with the main difference being the laser power used, typically applied in 3D printing of polymer materials.

The following is the process of preparing plastic parts using SLS.

Model Layer Slicing

Removing the Parts

Post-Processing

SLS can also be used to manufacture metal or ceramic parts, but the resulting parts have low density and require post-densification treatment before use.

SLS Manufacturing of Metal Parts

4. LMD (Laser Metal Deposition)

LMD, or Laser Metal Deposition, is a technology with many names, as different research institutions have independently studied and named it. Common names include LENS, DMD, DLF, and LRF. The main difference from SLM is that its powder is delivered to the work surface through a nozzle, where it converges with the laser at a point, melting and cooling to form a deposited entity.

The following is the working process of LENS technology.

Coaxial Powder Delivery

Building Process

5. EBM (Electron Beam Melting)

EBM, or Electron Beam Melting, has a process very similar to SLM, with the main difference being that the energy source used in EBM is an electron beam. The output energy of the electron beam in EBM is typically an order of magnitude greater than the laser output power in SLM, and the scanning speed is also much higher than that of SLM. Therefore, during the building process, the entire build platform needs to be preheated to prevent excessive residual stress due to high temperatures during the molding process.

The following is the working process of EBM.

Overall Preheating

Forming Process

Changes in Powder During Melting Process

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☞ Source: World Advanced Technology Manufacturing Forum ☞ Responsible Editor: Xu Peipei ☞ Proofreader: Wang Jiahui ☞ Reviewer: Wu Xiaolan ☞ Media Cooperation: 010-88379790-801

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