SLA (Stereolithography) 3D Printing Explained

SLA (Stereolithography) is a popular technology in the ever-evolving world of additive manufacturing. By harnessing the power of light to cure photosensitive polymers, SLA opens up design possibilities with precise and intricate prints featuring exceptional surface finishes.

This article delves into this 3D printing technology, exploring its core principles, materials, and applications. You’ll also learn the critical differences between SLA and Digital Light Processing (DLP), a similar additive manufacturing technology.

What is SLA?

Stereolithography (SLA) is a sophisticated additive manufacturing process that leverages the power of light to transform liquid resin into solid, three-dimensional objects.

This technology, also known as resin 3D printing or vat photopolymerization, involves curing photosensitive polymers layer by layer using a laser or other light source. The result is a highly accurate and detailed part with a smooth surface finish, making SLA a preferred choice for applications requiring precision and fine detail.

SLA utilizes the power of photopolymerization to transform liquid photopolymer resins into solid objects, layer by layer.

The process starts with a vat of liquid resin, and a precisely controlled laser beam selectively cures the resin, solidifying it into the desired shape. This layer-by-layer approach results in high-resolution prints with remarkable accuracy and fine details. The layer thickness, typically ranging from 10 to 100 microns, plays a crucial role in achieving these fine details and intricate geometries.

SLA Materials

SLA offers various materials, each with unique characteristics and applications. Photopolymer resins, specially formulated for SLA, include:

Standard Resins: These general-purpose resins suit various applications, including prototypes, concept models, and functional parts. They offer good mechanical properties, ease of use, and excellent surface finishes.

Flexible Resins: Flexible resins mimic the flexibility and elasticity of rubber. It’s ideal for producing parts that require bending, stretching, or compression. Applications include gaskets, seals, grips, and wearable devices.

High-Temperature Resins: Withstanding elevated temperatures, high-temperature resins are used for functional parts that experience heat, such as under-the-hood automotive components, molds, and tooling inserts.

Transparent Resins: Transparent resins enable the creation of clear and translucent parts suitable for applications like optics, light guides, lenses, and visual prototypes where visual clarity is essential.

Bio-Compatible Resins: These are safe for medical and dental applications.

Characteristics of SLA 3D Printing

SLA 3D printing is renowned for several key characteristics that make it a popular choice in various industries:

High Accuracy and Detail: SLA technology excels in producing parts with exceptional accuracy and intricate details, making it ideal for applications where precision is paramount.

Minimal visible layer lines: The layer-by-layer construction in SLA results in parts with minimal visible layer lines, ensuring a smooth surface finish that often requires little to no post-processing.

Support structures: To maintain the integrity of overhanging or delicate features during printing, SLA requires the use of support structures. These supports are printed alongside the part and are removed during post-processing.

UV Laser: The use of a UV laser or other light source to cure the resin is a defining feature of SLA 3D printing. This technology, while requiring specialized equipment, enables the creation of highly detailed and accurate parts.

Popular SLA Applications

SLA finds use across various industries thanks to its precision and ability to produce intricate parts. Some typical applications of SLA include:

Prototyping: SLA is widely used for rapid prototyping in product development, enabling designers and engineers to create functional prototypes with high accuracy and intricate details.

Engineering: SLA produces detailed components, functional prototypes, and tooling for these industries. It enables engineers to test and validate designs before manufacturing.

Dental and Medical Devices: SLA is used in dentistry to create models for orthodontic aligners, surgical guides, crowns, bridges, and other dental restorations. It’s also used in medical device production, such as hearing aids and customized prosthetics.

SLA Process Steps

The SLA 3D printing process begins with design preparation and ends with post-processing. These are the steps to turn your design into a finished part.

Design Preparation: Prepare the 3D model in CAD software, ensuring it is optimized SLA, which includes adding supports to ensure the stability of overhanging or delicate features.

If you’re using the MakerVerse platform, this is the primary step you must focus on. You can then upload your design and specify the needed materials and post-processing options. You’ll receive a quote in 24 hours and can choose to begin production. We’ll take care of the entire production process and ensure the industrial quality of your finished part.

Printer Preparation: If you’re using an in-house SLA printer, you’ll need to fill the resin vat with the desired photopolymer resin, ensuring proper leveling and calibration of the build platform.

Printing: Based on the sliced model data, the printer’s UV laser selectively cures the resin, solidifying it one layer at a time. The build platform lowers after each layer is cured, exposing the next layer.

The printer continues the layer-by-layer building process until the entire object is printed, each adhering to the previously cured layers.

Post-Processing: After the print is complete, the object is typically attached to support structures to prevent warping or collapsing during printing.

Once the print is removed from the printer, it undergoes post-processing steps. This may involve cleaning the print in isopropyl alcohol to remove excess resin, UV curing to cure the print fully, and removing any support structures.

When to use DLP vs. SLA 

SLA and Digital Light Processing (DLP) are resin-based 3D printing technologies with a lot of overlap in terms of capabilities. However, there are some differences.

Price: Price varies based on the material use and the parts being printed. DLP offers faster speeds, but is also a bit more complex to set up, which could offset any cost advantages. In this case, it’s essential to consider the material selection, production size, and other factors, as these can change the final price.

Precision: Both DLP and SLA technologies offer exceptional precision. In terms of dimensional accuracy, DLP has a slight advantage.

Surface Quality: SLA often excels in terms of surface quality and smoothness. While still capable of producing high-quality surface finishes, DLP may exhibit slightly more pronounced layer lines due to the projection-based curing process. However, post-processing techniques such as sanding, polishing, or applying surface finishes can be employed to achieve smooth surfaces for both DLP and SLA prints.

Getting Started with SLA

Are you ready to embark on your SLA journey? SLA is one of over a dozen manufacturing technologies available on the MakerVerse platform. Upload a part, specify the needed materials, and begin production.