Understanding the Differences Between SLA and DLP 3D Printing

In the realm of 3D printing, Stereolithography (SLA) and Digital Light Projection (DLP) are two prominent technologies, both utilising liquid resin to create detailed components. While these methods share similarities, each has distinct characteristics that make them suitable for different applications. At Prototype Projects, we offer both SLA and DLP services (as well as SLS, PolyJet and PµSL) to cater to your specific prototyping needs. Let’s explore the key differences between these two 3D printing techniques.

What is SLA 3D Printing?

Stereolithography (SLA) is a well-established additive manufacturing process that uses a UV laser to cure liquid resin into a solid, layer by layer. This technology is known for producing highly detailed parts with a smooth finish.

How SLA Works

Preparation

A thin layer of liquid resin is spread across the build platform inside a vat.

Laser Curing

A UV laser traces the cross-section of the CAD model, curing the resin layer by layer.

Layering

The platform moves, and a new layer of resin is applied and cured. This process continues until the part is complete.

Post-Processing

The printed part is rinsed to remove excess resin and typically undergoes additional curing to enhance its properties.

Advantages of SLA

High Detail

SLA can produce parts with intricate details and fine features, making it suitable for prototypes requiring high definition.

Smooth Finish

The parts created with SLA have a smooth surface, often requiring minimal post-processing for aesthetic purposes.

Versatile Materials

SLA resins can be formulated for a variety of properties, including transparency, flexibility, and high temperature resistance.

Disadvantages of SLA

Support Structures

SLA often requires support structures for overhangs and complex geometries, which need to be removed and can sometimes leave marks.

Fragility

Parts can be more brittle compared to other 3D printing methods, limiting their use in functional testing or high-stress applications.

Limited Build Volume

The build volume of SLA printers is generally smaller, which can restrict the size of the parts that can be produced.

What is DLP 3D Printing?

Digital Light Projection (DLP) is another form of additive manufacturing that uses a digital light projector to cure liquid resin into a solid. This technology is similar to SLA but has some notable differences, particularly in how the light source is used.

How DLP Works

Preparation

Liquid is poured into a vat that has a clear membrane at the base.

Light Projection

A digital light projector flashes a full image of each layer onto the resin, curing it all at once.

Layering

The platform is lowered into the vat very close to the membrane. A layer of a set height is then cured through the membrane onto the platform via projection. The platform is moved up to separate from the membrane and recoat in fresh resin. Then the platform and previous cured layer lower down to the membrane separated by the chosen layer thickness.

Post-Processing

The printed part is rinsed to remove excess resin and typically undergoes additional curing with heat and UV light.

Advantages of DLP

Speed

DLP can be faster than SLA because it cures an entire layer at once rather than tracing it with a laser.

Fine Features

DLP excels at producing small and delicate components with intricate details.

Material Properties

DLP materials tend to resemble production-grade materials more closely, offering enhanced mechanical properties after post-curing. More testing of the materials has been performed meaning the data sheets are far more detailed.

Disadvantages of DLP

Warping

The heat exposure during post-processing and the ‘peel-force’ applied during printing can cause components to warp or distort, especially for larger or more robust parts. We may advise a different process in those instances.

Support Structures

Similar to SLA, DLP requires support structures, which need to be removed and can affect the final surface quality.

Geometry Limitations

The likelihood of warping and distortion makes DLP less suitable for larger, thicker, more robust components.

Comparing SLA and DLP

Aspect	SLA	DLP
Light Source	UV laser	Digital light projector
Detail	High detail and smooth finish	Excellent for small, intricate parts
Speed	Slower, layer-by-layer curing	Faster, full-layer curing
Material Properties	Good, with a range of resin options	Closer to production-grade materials
Support Structures	Required for complex parts	Required for complex parts
Warping	Less prone to warping	More prone to warping and distortion
Build Volume	Much larger	Generally smaller, but can vary

Conclusion

Both SLA and DLP offer unique advantages that cater to different aspects of prototyping and production. SLA is ideal for creating detailed, smooth-finished parts, especially for robust applications, while DLP excels in producing small, intricate components with production-grade material properties. However, the choice between SLA and DLP largely depends on the specific requirements of your project.