Stereolithography (SL) is an industrial 3D printing process to create concept models, cosmetic prototypes, and complex parts with intricate geometries in as fast as 1 day. Stereolithography parts can be produced in a wide selection of materials, extremely high feature resolutions, and quality surface finishes are possible with SL.

Metal Plated Plastic Parts

Proto Labs in-house SL Plating provides metal coated 3D printed plastic parts that have the appearance and of metal, but the advantage of light weight plastics with added strength. The Plated finish is widely used in applications such as the automotive, electrical engineering and many other industries. 

Stereolithography design guidelines will help you understand capabilities and limitations.

Why Choose Stereolithography For Your 3D Printing Project?

SL is an excellent choice for project designs that require the production of very accurate and finely detailed parts. It’s ideal for producing show-and-tell parts to enable validation of concept ideas and ergonomic testing. We also offer a number of secondary services such and plating and painting to further enhance the finish of your 3D-printed project design. 

Stereolithography material data sheets can be found in our Material Comparison Guide

How Does Stereolithography Work?

The SL machine begins the 3D printing process by drawing the layers of the support structures, followed by the part itself, with an ultraviolet laser aimed onto the surface of a liquid thermoset resin. After a layer is imaged on the resin surface, the build platform shifts down and a recoating bar moves across the platform to apply the next layer of resin. The process is repeated layer by layer until the build is complete.

Newly built parts are taken out of machine and into a lab where solvents are used to remove any additional resins. When the parts are completely clean, the support structures are manually removed. From there, parts undergo a UV-curing cycle to fully solidify the outer surface of the part. The final step in the SL process is the application of any custom or customer-specified finishing. Parts built in SL should be used with minimal UV and humidity exposure so they don’t degrade.

1 to 50+ parts

Shipped in 1 to 7 days 

Best for:
  • cosmetic prototypes
  • form and fit testing
  • extremely small parts with fine details

Stereolithography Materials

We offer numerous material options that are regularly updated to meet prototyping and master fabrication needs. Our thermoplastic-like SL materials include grades of ABS, polycarbonate and polypropylene, along with a durable nickel-coating option. Depending on your part application, a range of characteristics are achievable: resolution, colour and clarity, stiffness and feel to durability, impact resistance, temperature tolerance, and water resistance.



Design Guidelines

Our basic guidelines for stereolithography include important design considerations to help improve part manufacturability, enhance cosmetic appearance, and reduce overall production time.



a metal 3D printing technician removes support structures from a DMLS part

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The Stereolithography Process

As with other additive manufacturing processes like SLS and DMLS, SL relies on lasers to do the heavy lifting. Parts are built by curing paper-thin layers of liquid thermoset resin, using an ultraviolet (UV) laser that draws on the surface of a resin turning it from a liquid into a solid layer.

As each layer is completed, fresh, uncured resin is swept over the preceding layer and the process repeated until the part is finished. A post-build process is required on SL parts, which undergo a UV-curing cycle to fully solidify the outer surface of the part and any additional surface finish requirements.

What are the material options for Stereolithography?

Unlike older generations of SL, today’s machines offer a range of thermoplastic-like materials to choose from, with several variants to mimic polypropylene, ABS, and glass-filled polycarbonate available. Proto Labs offers many variations of these materials:

View the Stereolithography Materials selector

  • Polypropylene: A flexible, durable resin that mimics a stiff polypropylene. It can withstand harsh mechanical treatment and is great for fine details—sharp corners, thin walls, small holes, etc.
  • Polypropylene/ABS blend: Strong, white plastic similar to a CNC machined polypropylene/ABS blend. It works well for snap fits, assemblies, and demanding applications.
  • ABS: Variations of ABS mimics include a clear, low-viscosity resin that can be finished clear; an opaque black plastic that blocks nearly all visible light, even in thin sections; a clear, colourless, water-resistant plastic good for lenses and flow-visualisation models; and a micro-resolution resin that enables production of parts with extremely fine features and tight tolerances.
  • Polycarbonate: A ceramic-filled PC material that provides strength, stiffness, and temperature resistance, but can be brittle.
  • SLArmor: A nickel-plated material that gives SL-generated parts much of the strength and toughness associated with die cast aluminium.


For a more detailed look at 3D printing and Stereolithography, read our white paper on choosing the right 3D printing materials.

Please refer to our materials comparison guide for further detail to support your material selection. Additionally, applications engineers at Proto Labs can help guide you during material and manufacturing process selection if help is needed.

For technical support, call Proto Labs on +44 (0)1952 683047 or email: to discuss the options available for your design.