Resin or synthetic resin is UV-curing liquid. The photosensitive resin can be cured by laser or light and thus transformed into a solid model. 3D printing Stereolithography (SLA) photopolymer resin uses additive manufacturing techniques to make printed parts from liquid resin. DLP (Digital Light Processing) & SLA 3D printing uses an LED light source with a digital micromirror device (DMD) to project layer-by-layer images on the build plate to form the final object. Some modern DLP 3D printers now have removed the DMD in favor of a panel of micrometer-sized LED lights. This projecting of the entire layer at once makes it one of the fastest photopolymer resin 3D printing technologies currently available. When using SLA technology, it is important to use the right material that is designed to work with DLP curing technology. Resin 3D printers produce incredibly accurate prints which are compatible with a wide variety of materials and can produce parts relatively quickly. These precision machines used to cost very high, but in recent years 3D printers have become very cheap. The liquid resin is exposed at the desired locations with the 3D printer, curing the resin. This technique makes it possible to produce components with high surface quality and very high level of detail. Resins have several material properties that it the advantage it has. So you can use the right Resin for every need.
All the three technologies use polymerization which involve a photosensitive resin cured by a light source to produce solid layers and form whole part. The resin is contained within a tank and is cured against a build platform, which slowly rises out of the tank as the part is formed. The main difference between the three technologies here is the light source.
The most well known and oldest of the three is Stereolithography (SLA). It uses a laser to cure the resin. The photopolymer resin is held in tray with a movable platform inside. A laser beam is directed in the X-Y axis across the surface of the resin, where the resin hardens precisely wherever the laser hits the surface. Once the layer is completed, the platform within the tray drops down by a fraction (in the Z axis) and the subsequent layer is traced out by the laser. This continues until the entire object is completed and the platform can be raised out of the tray for removal.
Instead of a laser, Digital Light Processing (DLP) uses a digital light projector to cure the resin. It flashes images of whole layers onto the bottom of the tray. Light is selectively directed using a digital projector or digital micromirror device (DMD).
LCD 3D printing is nearly the same as DLP. It also flashes complete layers at the resin tank, but with the UV light coming from an array of LEDs shining through an LCD, not a projector. A screen acts as a mask, revealing only the pixels necessary for the current layer. As such, no special device is required to direct the light, as is the case in both SLA and DLP.
There are many differences between the three main resin based 3D-printing techniques. The table below shows the basic differences.
| SLA | DLP | LCD | |
|---|---|---|---|
| Build Area | ++ | – | + |
| Price | - | - | ++ |
| Speed | + | ++ | - |
| Quality | ++ | ++ | + |
The benefit that both DLP and LCD share, when compared to SLA, is build speed. Because there’s an entire layer is flashed at once, instead of a single point. The two technologies are typically able to produce parts faster. Looking at the market, the general trend is that DLP printers are the more expensive, professional machines. LCD, a more recent technology, has so far been seen mostly in affordable, desktop printers. As mentioned earlier, cheaper DLP printers sometimes suffer from minor pixel distortion. That issue becomes less of a problem if one invests a little more money, that is because with higher quality printers comes higher quality hardware which is designed to correct for distortion. In general, LCD 3D printers use cheaper components than DLP 3D printers, making them a cheaper resin 3D printing solution. This is a great thing because it extends the reach of resin 3D printing to a wider audience of makers. Both DLP and LCD are able of achieving fast print speeds and great details, but as the price tag grows, the DLP 3D printers start to trump their LCD counterparts. If you’re a professional who needs high detail and fast print speeds, we’d suggest that you look into professional DLP printers. On the other hand, if you’re a beginner to resin 3D printing, LCD would be a great choice.
Not all resins are compatible with the different printing techniques. It is important to read the resin manufacturers datasheets to understand if it is compatible with your 3D-printer. Laser based 3D-printers have a very powerful laser, which would need a slower curing resin to get a stable printing process. While LCD based 3D-printers have a low power LED light source, which works very well with fast curing resins. DLP 3D-printers can be configured in many different ways, making it impossible to predict curing behavior of the resin without testing.