Stereolithography (SLA) 3D Printing Materials and Process

Stereolithography (SLA), the first commercialized 3D printing technology, was invented by 3D Systems‘ Co-Founder and Chief Technology Officer Chuck Hull in the 1980s. It uses an ultraviolet laser to precisely cure photopolymer cross-sections, transforming them from liquid to solid. You can directly print items with CAD files, layer-by-layer for prototypes, investment casting patterns, tools, and end-use products.

SLA 3D printing, or resin 3D printing, has been widely used for its ability to produce high-accuracy, isotropic, and waterproof prototypes and pieces with excellent features and smooth and finished surfaces in a range of advanced materials.

How Does Stereolithography SLA Work?

Design

Use any CAD software or 3D scan data to design your model, and export it in a 3D printable file format (STL or OBJ).

Print

SLA printing works by first positioning the build platform in the tank of liquid photopolymer at a distance of one layer height for the surface of the liquid.

Then, a UV laser creates the next layer by selectively curing and solidifying the photopolymer resin. During the solidification part of the photopolymerization process, the monomer carbon chains that compose the liquid resin are activated by the light of the UV laser and become solid, creating unbreakable and strong bonds between each other.

The laser beam focuses on a predetermined path using a set of mirrors – galvos. The whole cross-sectional area of the model is scanned so the produced part is solid.

After printing, the part is in a not-fully-cured state. It requires further post-processing under UV light for very high mechanical and thermal properties.

The photopolymerization process is irreversible. And there is no way to convert the SLA parts back to their liquid form. Heating these SLA parts will cause them to burn instead of melting. This is because materials with SLA are made of thermoset polymers.

Post-Process

After finishing the material polymerization, the platform rises out of the tank. And the excess resin is drained. At the end of the process, the model is removed from the platform, washed of excess resin, and then placed in a UV oven for final curing. Post-print curing enables objects to reach the highest possible strength and become more stable.

The Characteristics of SLA 3D Printing Materials

SLA resins offer the most accurate fit/form prototypes for design verification before committing to production. High accuracy and excellent surface finish make these resins the preferred choice for designer models, engineering verification, and master patterns for silicone and rubber molds.

SLA materials are available in a wide range of mechanical properties, which can produce parts with characteristics similar to injection-molded ABS or polypropylene, suitable for applications such as snap-fit assemblies, automotive styling components, and master patterns, as well as higher-temperature applications and exceptional clarity. Resins for higher-temperature applications and transparent materials with polycarbonate-like properties are also available. Our SLA material portfolio also includes biocompatible materials suitable for a wide range of medical applications, such as surgical tools, dental appliances, and hearing aids. Other SLA materials have been specifically formulated for sacrificial investment casting patterns, offering low ash creation and high accuracy while also being expendable.

Rigidity: Similar aesthetics and properties to injection-molded ABS

Tough & Durable: Similar touch feeling and exterior to polypropylene

Transparent: The industry’s highest-clarity material for polycarbonate-like parts

Castable: Expendable resins specifically formulated for QuickCast® sacrificial patterns for investment casting.

High Temperature: Heat deflection temperatures over 215˚C (419°F) offer exceptional performance under extreme conditions.

Specialty Materials: Options for jewelry-specific casting and dental models’ production

Advantages of SLA 3D Printing

Produce parts with very high dimensional accuracy and with intricate details.

Parts have a smooth surface finish, making them ideal for visual prototypes.

Available Speciality SLA materials, such as transparent, flexible, and castable res

Disadvantages of SLA 3D Printing

The mechanical properties and visual appearance of SLA parts will degrade over time when the parts are exposed to sunlight.

Steep slopes and overhangs require support structures during the building process. Such parts may potentially collapse during the printing or curing phases.

Resins are comparatively fragile. Therefore, they are not suitable for functional prototypes or mechanical testing.

SLA offers limited material and color choices, usually black, white, grey, and transparent. Resins are often proprietary. Thus, they are not changeable between printers from different brands.

SLA Applications

Delivering the smoothest surface finish of any additive manufacturing process, the quality of SLA parts makes this versatile technology great for:

General

• Design verification models for appearance and proof-of-concept models
• Functional prototypes and models for form and fit testing
• Wind-tunnel test models
• High clarity, transparent products and components
• Complex assemblies
• Under-the-hood components
• Mass customization

Tooling and patterns

• Investment casting patterns
• Sacrificial patterns for metal casting
• Custom assembly jigs and fixtures
• Tools, molds and dies
• Cast urethane/vacuum casting master patterns

Biocompatible materials

• Surgical tools/guides
• Dental appliances
• Hearing aids

Contact WKproto now if you need SLA 3D printing！