Types of 3D Printing : SLA, First 3D Printer

SLA (Stereolithography) is a type of 3D printing technology that creates a model, layer by layer, using a liquid photopolymerizable resin.
SLA printers are commonly divided into three types depending on the light source used to create the image: laser, DLP, and LCD.


In a previous blog, we discussed some of the various properties of the materials. Today, we will introduce more diverse materials and properties so that you can choose the material that best suits your needs and purpose.

Before choosing a material in the 3D printing process, it is important to consider which type of 3D printing technology to choose. There are many different type of technology for 3D printers, and each type has its own characteristics.

Let's take a brief look at the types of 3D printer technology.

 1. What was the first type of 3D printer?

The most common types of 3D printing technology include FDM/FFF using thermoplastic filament, SLA using photocurable resin, and SLS using polymer powder to sinter in a flat state. In the 3D printing industry new technologies are constantly being developed.

The first 3D printer was an SLA invented in 1986, this process works by curing a photopolymer with an ultraviolet laser and was first commercialized in 1987 by 3D Systems.

Shortly after, methods such as SLS and FDM (FFF) appeared one after another, but SLA took the title of being the first 3D printing technology.

 2. SLA and Photopolymerization

SLA (Stereolithography) is a technology that creates a model, layer by layer, using liquid photopolymerizable resin. Photopolymerizable resins are composed of photopolymerizable monomers, oligomers, and photoinitiators.

When the resin is filled into a tank, a laser beam is exposed to the desired part on a horizontal plane in a scanning method. As the photoinitiator is activated, the resin in the light is cured by continuous cross-linking of monomers and oligomers to form a polymer, while the remaining part remains as a liquid. 

Once one layer is complete, the process is repeated with the next layer until the model is finished.

The wavelength of the light source is selected according to the wavelength to which the photoinitiator responds. In the case of Desktop SLA models, near ultraviolet (385~405μm) is most commonly used, and in the case of industrial products, other wavelengths are sometimes used.

SLA 3D printing has the advantages of fast printing speed, excellent precision, and a clean surface. On the other hand, it also has disadvantages, such as the need for washing and secondary curing after printing, and the weak strength of the printed product.

SLA 3D printing technology is being used in various fields, and SLA types vary in materials as well as the characteristics of the printer itself. SLA technology is widely used in the dental field, where the supply of 3D printers is rapidly growing worldwide, as well as in the medical, engineering, jewelry, model (figure), and education markets. 3D printers are widely used in the production of prostheses in dental laboratories, and many start-up companies are heating up the certification and production of surgical guides.

As shown below, SLA 3D printers used in various industries are largely divided into laser, DLP, and LCD according to the type of light source. Of course, as in other industries, the hybrid method, which is applied in combination with the advantages of each light source method, is gradually being introduced to the market.


<Fig 1. Three type of SLA Printer>

3. Laser SLA

Generally, SLA refers to laser SLA.
As it cures point by point, the printing speed is slow, but in principle, there is no limit to the resolution.
The higher the resolution, the greater the precision.
The build area is also not limited in principle if the size of the printer is not taken into account.
However, a disadvantage is that the printing speed is very slow compared to the DLP or LCD method.


A DLP projector exposes the layers in one step, and selectively cures the resin in the presence or absence of a DLP pixel signal.
It can print much faster than laser SLA, and it is also faster than LCD because it has better light efficiency than LCD.
However, there is a disadvantage that the dimensional accuracy deviation between the center and the edges of the print may occur due to image distortion that may occur due to the use of a projector.

It is also called MSLA (Masked SLA), and the printer price is relatively cheaper than above methods because LCD is cheaper.
The LCD is located under the resin tank, so the size of the LCD is the same as the build area, and the close proximity of the LCD and resin tank enables a compact printer. Another advantage is that there is no image distortion that can occur with DLP.
But for the same reason, the resin tank is easily heated by the LED matrix, so an effective cooling system is required.

SLA LCD Sindoh Dental

 <Fig 2. Example of SLA printer and Use case> 


So far today, we have discussed the types of SLA printers among 3D printers.
SLA printers are known for their accuracy and smooth surface quality. SLA technology is being used in many industries due to the diversity of the materials including biocompatible certified resin and clear resin.

Do you have any plans to operate an SLA-based 3D printer in your industry?

Next, let's look at the types of FDM/FFF printers that use filament resin.

Thanks for joining us.


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