Stereolithography or SLA is an additive manufacturing process that was first introduced and invented way back in 1986. In fact, SLA was the technology used to manufacture the very first 3D printed parts. The SLA method utilizes a vat photopolymerization process and the materials used in SLA are mostly thermoset polymers that come in a liquid form. This 3D printing method provides extremely high detail without introducing excessive costs. As with any manufacturing method, designers must take advantage of the benefits and limitations of the SLA manufacturing process in order to achieve the best results. At SD3D, we utilize our in-house design expertise to make the entire process cost-effective while producing extraordinarily accurate and detailed parts.
How it Works
SLA works on the principle of photopolymerization by using a high-powered laser that hardens the polymer in accordance with the CAD design. The build platform is positioned at a distance of one-layer height from the surface of the liquid in the resin tank of liquid polymer. A UV laser then creates the next layer by selectively curing and solidifying the photopolymer resin. The cross-sectional area is continuously scanned to ensure that each layer is completely solidified before moving on to the next layer.
When a layer is finished, the platform is moved at a safe distance and sweeping blade recoats the surface with a polymer. This process is repeated several times until the entire part is produced.
The finished part is removed from the printer and washed in rubbing alcohol to get the excess resin off. If the part required supports during the build process, these are removed after the print is complete to get the final prototype. After that, you can do additional post-processing by passing the part through UV light to achieve parts with relatively high mechanical and thermal properties.
Materials used in SLA 3D Printing
SLA materials usually come in the form of liquid resin. The materials (thermosets) used in SLA are more brittle when compared to FDM or SLS (thermoplastics) and hence usually cannot be used for functional thin walled prototypes. However, advancements in materials will help resolve this issue over time.
Some of the common materials and their properties are given below.
- Standard Resin
- Smooth surface finish. Relatively brittle.
- Clear Resin
- Transparent material. Required post-processing for a very clean finish.
- Castable Resin
- Used for creating mold patterns. Low ash percentage after burnout.
- Tough or Durable Resin
- ABS-like or PP-like mechanical properties. Low thermal resistance.
- High-Temperature Resin
- High-temperature resistance. High cost. Used for injection molding and tooling.
- Dental Resin
- Biocompatible. High abrasion resistant. High cost.
- Biocompatible. High abrasion resistant. High cost.
SLA 3D Printer Terminology
Types of SLA Machines
You will commonly find SLA machines offered in two distinct formats:
- Desktop SLA 3D printers – used for manufacturing small (smaller-than-a-fist) injection molded-like parts at an affordable price.
- Industrial SLA 3D printers – used for producing very large parts (as big as 1500 x 750 x 500mm).
Benefits of SLA 3D Printing
SLA 3d printing provides some benefits over other AM technologies, especially when it comes to accuracy and smooth surface finishes. Let us look at some of the benefits.
- Above all, the parts produced with SLA are incredibly detailed. The layers can be produced down to 4 times finer than a human hair.
- You have a whole library of materials to choose from. Above all, this flexibility in material selection allows SLA to be used in many different applications.
- SLA parts are extremely durable when compared to other AM technologies. The SLA 3D print process creates a chemical bond between the layers and hence the finished parts require great force in order to break them.
- SLA 3d printing is ideal for visual prototypes from a range of thermoset materials. Furthermore, it provides the smoothest surface finish of all the 3D printing methods.
There are nearly endless operation opportunities to use SLA processing for 3D printing applications. Contact us to discuss your next SLA 3D printing project.
One of the cons of using SLA technology is the brittleness of manufactured parts. Therefore, the SLA 3D printing method may be unsuitable for some functional prototypes. Removal of support structures and post-processing is necessary to remove the visual marks on the SLA part. However, for thin parts the removal of support structures may damage the part itself.
Even while considering the disadvantages of using SLA vs other methods, it truly stands out when high accuracy and parts with high tolerances are required. For example, SLA would be considered an excellent choice for design patterns, molds, and small intricate parts. In conclusion, the SLA 3D printing process is an excellent choice for manufacturing of complex models, jewelry, and dentistry, etc.
