The Differences Between SLA and DLP 3D Printing

While SLA 3D printing and DLP are different technologies, they also have similarities. They both expose liquid photopolymers to a light source and are designed to print small models with precise details because of the resin tank. These methods are compatible with flexible or rigid materials and can print composite materials such as filled glass or ceramics. However, the printed parts are relatively fragile. Products are prone to deterioration if exposed to sunlight and may warp, too. SLA VS DLP 3D Printing, do you know the differences?

What Is SLA 3D Printing?

Stereolithography (SLA) was the first 3D printing technology developed in 1984 and is now considered one of the most precise 3D printing technology. Unlike DLP, the light source used in SLA is a laser. A laser beam sweeps across a resin tank that moves on a horizontal axis, curing the material layer by layer. There are now two kinds of machines — one acts from top to bottom, and each layer has a board descending with a new layer. The other is a machine in which the laser is from the bottom to the top. There is a platform that rises with your moving. SLA supports smooth surfaces and thicknesses up to 0.05 to 0.01 mm, allowing the printing of products with thin layers.

What Is DLP 3D Printing?

Digital Light Processing (DLP) comes from image projection technology using a projector as a light source. In this way, a single cast light affects the entire resin tray at once. The core part of the process is a digital micromirror device that sits between the projector and the resin. It is individually controlled and activated by several microscopic mirrors. Once the mirrors are activated, they reflect light onto the resin and light cure. Thus, they create a mask that hardens the resin according to the desired pattern. Some 3D printers have replaced the DMD with an LCD screen, significantly reducing the machine’s price.

SLA VS DLP 3D Printing

The DLP process is faster than stereolithography because it does not work point by point. Also, DLP printers are bigger than SLA machines due to their projectors. In most cases, the resin tanks on DLP machines are a bit shallower than those used in SLA processes.

Finally, the difference between SLA and DLP technologies is maintenance. DLP printers require little maintenance and are generally accessible to service, and the presence of lasers in SLA machines is deeply up to their maintenance service.

Quality

The finished product quality is often the deciding factor in choosing between the two technologies. When 3D printing is used to produce terminal parts, the details, structure, and surface level play a vital role in 3D printing technology selection. These two techniques make it possible to design the most detail-accurate and high-resolution models.

However, the decisive factors for printing quality are not only the process itself but also the selection of the material. The latter offer depends on the manufacturer, and most machines are closed for compatibility.

With the SLA, the resin is polymerized point by point. The longer the part, the longer it takes to print because the laser has to through the entire bed. Therefore, SLA is more suitable for printing objects between a few millimeters and 1.50 meters in length. It has no quality loss due to the length of products and can realize up to 25 microns resolution. The quality is independent of model size.

DLP allows up to 5 microns of thickness for each layer. However, it can create a “staircase” phenomenon on the final product due to the projection of the pixels, which affects the surface of the printed part. When printing long items, quality loss can occur on the sides because the center receives the most concentrated energy from the projector and its light then spreads out at the edges.

Printing speed

DLP is leading the way in printing speed since DLP cures the entire resin layer in one go. Unlike the SLA, where the resin is polymerized point by point, only the product height affects the printing speed in DLP.

Printing Volume

Stereolithography is not always for large parts production because of the high cost of materials compared to other processes such as FDM. In addition, the print volume is limited by the size of the canister containing the liquid resin.

The Formlabs 3L SLA printersupports size of 335 x 200 x 300 mm and the 3D Systems Pro X 950 is 1500 x 750 x 550 mm. DLP printers, the Envision TEC Xtrem 8K supports 450 x 371 x 399 mm, and the Carima DM400A model is for size 400 x 330 x 500 mm.

 Post-Processing

Post-processing for all resin 3D printing parts is mandatory. When printing thin models, it needs a support structure, which must be removed after curing. It can be time-consuming for this step and may be one of the leading drawbacks of resin 3D printing. Post-processing differences are mostly related to the materials used in SLA and DLP processes. In addition to cleaning parts from liquid resin with isopropyl alcohol (IPA) or tri-propylene glycol monomethyl ether (TPM), it also includes drying, support structures removal, possible post-curing, and sanding and painting if necessary.

Post-processing in SLA and DLP processes is not only time-consuming but also expertise demanded, or you can ask for help from experts. Post-processing in 3D printing is often a challenge which is why some companies have specifically optimized or automated it.

Application Cases

When using cases, SLA and DLP technologies are in similar industries. In particular, resin 3D printing is usually used in jewelry and dentistry. For example, manufacturer Formlabs offers a variety of resins for medical professionals. Many companies use them to make various medical devices, such as surgical guides. However, due to the wide variety of materials available, many other sectors also use resin 3D printing. No matter for prototyping, injection molds, or even engineering, there are several suitable resins.

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