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What is the difference between DLP and SLA light-curing 3D printers?

There are many different 3D printing technologies on the market. Familiarizing yourself with the nuances of each can help clarify what you want in the final print, allowing you to ultimately determine which technology is right for your specific needs. DLP and SLA 3D printing technologies are the two most common processes for 3D printing using photosensitive resin. Resin 3D printers are widely used to produce high-precision prototypes and parts made from a range of advanced materials with excellent functionality and smooth surface finishes. Both technologies used to be complex and costly, but as the technology has matured, today’s small desktop DLP or SLA 3D printers are cheaper than ever and can produce industrial-quality parts that can be printed thanks to a wide variety of material options. Objects can cater to different needs.
What is the light-curing 3D printing technology?
Some people may have heard of light-curing 3D printers, but they don’t know that light-curing 3D printers are also divided into SLA and DLP. What’s the difference between the two?

First of all, let’s talk about what light-curing 3D printing technology is. Its principle is to print objects layer by layer. The printing materials used are different from the rolls of plastic filament used in FDM 3D printers. The printing material used by light-curing 3D printers is liquid photosensitive resin. This photosensitive resin will produce a chemical reaction and solidify when exposed to light. A light-curing 3D printer prints a solid model by shining light onto the liquid photosensitive resin. In terms of accuracy, objects printed with light-curing technology are more detailed than objects printed with FDM or other printing technologies and are suitable for making fine models, such as jewelry prototypes, fine parts, etc. Light-curing 3D printing technology is divided into two types, namely DLP printing technology and SLA printing technology. The main difference between the two 3D printing technologies is the way they shine light onto the photosensitive resin that is the printing material.

What is DLP 3D printing technology?
DLP (Direct Light Processing) light-curing 3D printer has a built-in light projector. The DLP 3D printer uses the projector to project light onto the photosensitive resin of the printing material to solidify the resin. Due to the layered printing method, the 3D model will first be cut into layers horizontally by the 3D printing software, and then the DLP projector will be used to project the shape and pattern of the first layer of the 3D model onto the liquid photosensitive resin, making The photosensitive resin is light-cured and formed. After the first layer is printed, the printing platform will rise, so the printed object will also rise at the same time. Then the projector will project the shape pattern of the next layer of the 3D model onto the photosensitive resin, so repeated layered printing finally prints the object into shape. It is worth mentioning that during printing, the printed objects are printed upside down, which is different from FDM printing technology. Because DLP uses a projection of fluorescent light to shine a single image of each layer onto the printing platform, the image of each layer is formed by tiny squares called pixels.

What is SLA 3D printing technology?

As for SLA (Stereolithography) 3D printing technology, it does not use a light projector but uses a laser to shoot the laser onto the liquid photosensitive resin, solidifying the photosensitive resin layer by layer, and finally obtaining the shape of the entire object. When an SLA light-curing 3D printer emits a laser, it will not emit a whole layer of 3D model pattern like a DLP machine. The laser emits the liquid resin point-by-point to form a solidified layer. The main elements of an SLA light-curing printer are similar to that of a DLP printer, including a liftable printing platform. When the first layer of photosensitive resin solidifies, the platform will rise a certain distance, and then the second layer will be printed with a laser, and so on. Layers are printed layer by layer, finally printing into an overall shape. There is also a container containing liquid photosensitive resin. In addition, SLA uses two motors, one located on the X-axis and the other on the Y-axis. The motor will aim the laser at the specified printing coordinates to solidify the resin at that location. Through 3D slicing software, the 3D model will be analyzed into a series of points and lines with different coordinates. The SLA machine will accurately hit the laser on the printing material, liquid resin, according to the coordinate path.
Since the light projection methods of SLA and DLP light-curing 3D printers are different, the printing time of SLA will be longer, especially when printing large objects, and the printing time of DLP light-curing 3D printers will be much shorter. However, in terms of the relative printable area, since DLP uses projection, the relative printable area is smaller, while SLA is not affected by projection, so the printable area is not limited.

What are the main differences between DLP and SLA light-curing 3D printers?
The main difference between DLP and SLA is the light source. SLA generally uses a UV laser beam, while DLP uses UV light emitted by a projector. In DLP, the UV light source remains stationary, and the entire resin layer is cured at once. In SLA, a laser beam tracks the points of the geometry to be printed and moves between points. Because DLP 3D printers cure the entire resin layer at once, DLP runs faster and greatly reduces 3D printing time.

In DLP 3D printers, operators can control the intensity of the UV light source and, thus, its effect on the resin. In SLA, there is no way to adjust the intensity of the laser beam, you have to completely change the laser to create a different resin effect. UV light sources in DLP are inexpensive and can be easily replaced. In comparison, laser lights are more expensive. DLP is suitable for making multiple identical parts at one time.

The figure below shows the difference between SLA and DLP printing:

On the other hand, it is worth noting that there is a direct relationship between the resolution of a DLP 3D printer and the printable volume. The resolution (accuracy) depends on the projector inside the DLP 3D printer, which defines the number of pixels or pixels available. If you move the projector closer to the optical window, the pixels become smaller, which increases resolution but limits the area that can be printed. Therefore, DLP 3D printers can increase the resolution of 3D model printing by reducing the printing volume. Some have smaller print volumes, such as small and delicate parts such as jewelry, which require high resolution to produce.
As for the SLA 3D printer, because it uses a laser beam, its printable volume is independent of the printing resolution. A single print can be printed anywhere within the printable area and at any size. Therefore, if you print some large-volume models and do not need ultra-high resolution, SLA will be very suitable.

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