3D printing is an emerging technology in the manufacturing sector, known as a “manufacturing technology of industrial revolution significance.” In recent years, with advancements in industrial technology, 3D printing technology has rapidly developed and gained widespread media attention, with various 3D printing technologies being reported.
Below, I will share the principles of 3D printing in the polymer and metal categories, mainly introducing five major polymer technologies: SLA, CLIP, 3DP, PolyJet, and FDM, as well as five major 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 to initiate a polymerization reaction, layer by layer curing and generating a three-dimensional entity. The dimensional accuracy of parts produced by SLA is high, making it one of the earliest commercialized 3D printing technologies.
Below is the SLA process engineering:
Ultraviolet Laser Source
Photo-Curing Reaction
Layered Scanning Molding
2. CLIP (Continuous Liquid Interface Production Technology)
CLIP is a revolutionary 3D printing technology developed by Carbon 3D based on SLA technology, which increases the speed of 3D printing by 100 times!
CLIP projects from the bottom, curing photosensitive resin, while controlling oxygen to form a dead zone that suppresses the photo-curing reaction, maintaining a stable liquid area, thus ensuring the continuity of curing.
Photo-Curing Reaction
Oxygen Suppressing the Photo-Curing Process
Photo-Curing Dead Zone Demonstration
CLIP Molding Process
3. 3DP (Three-Dimensional Printing)
3DP, or three-dimensional printing rapid prototyping technology, is similar to traditional two-dimensional inkjet printing, where a binder (colored binder can print colored parts) is sprayed from the nozzle to bond powder on the platform to form a shape, typically using gypsum powder as the forming material.Currently, 3DP technology has two main applications:full-color 3D printing and sand mold casting.
Below is the process of sand mold casting using 3DP technology by Exone:
Binder Jetting
Heating and Curing
Printing and Forming
Casting Formation
PolyJet is a polymer jetting technology, whose molding principle is similar to 3DP technology, but instead of a binder, light-curable resin is jetted, and after spraying, it is cured by ultraviolet light.
PolyJet Molding Principle
PolyJet uses an array of nozzles and can even simultaneously spray 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, uses high temperatures to melt materials, extruding them through a print head to accumulate and form on the component platform.FDM is the simplest and most common 3D printing technology, typically used in desktop-level 3D printing devices.
Below 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 and manufacturing of metal parts, with broad industrial application prospects. It is a key development technology for 3D printing both domestically and internationally. Below, I will share the principles of five major metal 3D printing technologies: NPJ, SLM, SLS, LMD, and EBM.
6. NPJ (Nano Particle Jetting)
NPJ technology is a recently developed metal 3D printing technology by the Israeli company Xjet. Compared to ordinary laser 3D printing, it uses nano liquid metal, depositing it in a jetting manner, achieving five times the printing speed of ordinary laser printing, and possesses 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
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 spot to quickly 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. Below is a working diagram of the scanning system from SLM Solution:
Laser Scanning and Melting
Metal Powder Melting Process
In the metal 3D printing process, due to the complexity of the parts, support materials are usually required. After the part is completed, supports need to be removed, and surface treatment is often necessary.
3. SLS (Selective Laser Sintering)
SLS, or Selective Laser Sintering, is a technology similar to SLM, differing mainly in the laser power used, and is typically used for 3D printing of polymer materials.
Below is the process of preparing plastic parts using SLS:
SLS can also be used to manufacture metal or ceramic parts, but the density of the resulting parts is low and requires post-densification treatment to be usable.
SLS Manufacturing Metal Parts
4. LMD (Laser Metal Deposition)
LMD, or Laser Metal Deposition, is a technology with many names, as different research institutions independently study and name it. Common names include: LENS, DMD, DLF, LRF, etc. The main difference from SLM is that its powder is gathered to the working surface through a nozzle, converging with the laser at one point. After melting, the powder cools to form a piled-up cladding entity.
Below is the working process of LENS technology:
5. EBM (Electron Beam Melting)
EBM, or Electron Beam Melting, has a process very similar to SLM, with the main difference being that EBM uses an electron beam as the energy source. The energy output of the electron beam is usually an order of magnitude greater than that of the SLM laser, and the scanning speed is also much higher than SLM. Therefore, during the construction process, it is necessary to preheat the entire build platform to prevent excessive residual stress caused by high temperatures during the forming process.
Below is the working process of EBM:
Changes in Powder During Melting
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