What is Stereolithography (SLA)?

Stereolithography (SLA) is a 3D printing technique used to produce concept models, cosmetic prototypes, and detailed parts with complex geometries. This additive manufacturing process works by curing thermoset resin using a UV laser, layer by layer. SLA offers a wide range of materials, high resolution for intricate details, and excellent surface finishes.

SLA 3D printing is commonly used for:

  • Parts that require high precision, with features as small as 0.002 inches
  • Creating prototypes with smooth surface finishes
  • Form and fit testing for design validation

SLA Design Guidelines and Capabilities

Our fundamental guidelines for stereolithography focus on key design factors that optimize part manufacturability, improve the cosmetic quality of prototypes, and minimize production time.

US Metric
Normal Resolution 29 in. x 25 in. x 21 in. * 736mm x 635mm x 533mm
High Resolution 10 in. x 10 in. x 10 in. 254mm x 254mm x 254mm
Micro Resolution 5 in. x 5 in. x 2.5 in. 127mm x 127mm x 63.5mm
US Metric
Normal Resolution 0.004 in. 0.1016mm
High Resolution 0.002 in. 0.0508mm
Micro Resolution 0.001 in. 0.0254mm
US Metric
Normal Resolution X-Y: 0.010 in.
Z: 0.016 in.
X-Y: 0.254mm
Z: 0.406mm
High Resolution X-Y: 0.005 in.
Z: 0.016 in.
X-Y: 0.1016mm
Z: 0.406mm
Micro Resolution X-Y: 0.0025 in.
Z: 0.008 in.
X-Y: 0.0635mm
Z: 0.203mm
US Metric
Normal Resolution 0.010 in. 0.254mm
High Resolution 0.004 in. 0.1016mm
Micro Resolution 0.0025 in. 0.0635mm
US Metric
Normal Resolution 0.025 in. 0.635mm
High Resolution 0.020 in. 0.508mm
Micro Resolution 0.015 in. 0.381mm

SLA Tolerances

For properly designed parts, the typical tolerances are ±0.002 in. (0.05mm) in the X/Y dimensions for the first inch, plus 0.1% of the nominal length (0.001mm/mm), and ±0.005 in. in the Z dimension for the first inch, plus 0.1% of the nominal length. Keep in mind that tolerances may vary depending on the geometry of the part.

*Compatible with the following materials: ABS-Like White and Gray, ABS-Like Translucent/Clear, and PC-Like Translucent/Clear.

SLA Material Options

ABS-Like White (Accura Xtreme White 200) is a popular, versatile SLA material commonly used for functional prototypes. Offering a balance of flexibility and strength, it falls between molded polypropylene and molded ABS, making it ideal for a variety of applications. With the ability to build parts as large as 29 in. x 25 in. x 21 in., it’s a top choice when a larger build size is required.

Key Benefits:

  • Durable, all-purpose resin
  • Capable of handling extra-large parts

ABS-Like Gray (Accura Xtreme Gray) is a commonly used, versatile SLA material known for its balance of flexibility and strength, which places it between molded polypropylene and molded ABS. This makes it an excellent option for functional prototypes. ABS-Like Gray also boasts the highest heat deflection temperature (HDT) among the ABS-like SLA resins.

Key Benefits:

  • Durable, all-purpose resin
  • Highest HDT among ABS-like SLA resins

ABS-Like Black (Accura 7820) is a popular general-purpose material recognized for its rich black color and glossy top surfaces, giving parts the look of molded components. However, layer lines may be visible from the side profile. Accura 7820 also features low moisture absorption (0.25% per ASTM D570), enhancing the dimensional stability of parts. When compared to other SLA materials, it offers midrange mechanical properties.

Key Benefits:

  • Low moisture absorption for improved stability
  • Glossy, molded-like cosmetic finish

ABS-Like Translucent/Clear (WaterShed XC 11122) provides an exceptional combination of low moisture absorption (0.35% per ASTM D570) and near-colorless transparency. Achieving full clarity may require secondary operations, and the part will retain a faint blue hue. While suitable for general-purpose applications, WaterShed is especially ideal for flow-visualization models, light pipes, and lenses.

Key Benefits:

  • Lowest moisture absorption among SLA resins
  • Functional transparency

MicroFine™ is a proprietary material offered in gray and green, exclusively available at Protolabs. This ABS-like thermoset material is printed using Protolabs’ specialized machinery to achieve high-resolution features as small as 0.002 in. MicroFine is perfect for producing small parts, typically under 1 in. by 1 in. by 1 in. In terms of mechanical properties, MicroFine ranks in the mid-range for tensile strength and modulus, but on the lower end for impact strength and elongation.

Key Benefits:

  • Produces parts with the highest resolution
  • Ideal for very small parts

PP-Like Translucent White (Somos 9120) is one of the most flexible SLA materials available, second only to Carbon RPU 70 and FPU 50. When compared to typical injection-molded polypropylene, 9120 exhibits similar tensile strength, tensile modulus, flexural modulus, and impact strength. However, its elongation is only 25% of that of molded polypropylene.

Key Benefits:

  • Semi-flexible
  • Translucent properties

PC-Like Advanced High Temp (Accura 5530) produces robust, rigid parts with excellent high-temperature resistance. A thermal post-cure treatment can enhance the heat deflection temperature (HDT) up to 482°F at 0.46 MPa loading. Accura 5530 has the highest E-modulus among all unfilled SLA materials and is particularly resistant to automotive fluids. However, the thermal curing process reduces elongation by 50%, making it less flexible.

Key Benefits:

  • High elastic modulus
  • Enhanced resistance to heated fluids

PC-Like Translucent/Clear (Accura 60) is an alternative to general-purpose ABS-like materials and WaterShed XC 11122 when greater stiffness is required. Similar to WaterShed, this material can be further processed to achieve functional transparency. Accura 60 boasts the highest tensile strength and elastic modulus of all SLA materials, aside from the thermal-cured Advanced High Temp options.

Key Benefits:

  • High stiffness
  • Functional transparency

Ceramic-Like Advanced HighTemp (PerFORM) offers the highest tensile strength and E-modulus, making it the stiffest performance material among SLA options. When subjected to thermal curing, PerFORM achieves the highest heat deflection temperature (HDT) of up to 514°F at 0.46 MPa loading, surpassing other SLA materials.

Key Benefits:

  • Stiffest SLA resin
  • Highest HDT among SLA resins

True Silicone is 100% pure silicone, available in various shore-A hardness levels as listed below. This material is ideal for creating both functional prototypes and end-use products. It offers excellent resistance to harsh environmental conditions, as well as to acids, bases, and nonpolar solvents.

SLA Material Property Comparison

Material Color Tensile Strength Tensile Modulus Elongation
ABS-Like White (Accura Xtreme White 200) White 7.9 ksi 479 ksi 9%
ABS-Like Gray (Accura Xtreme Gray) Gray 5.8 ksi 290 ksi 9%
ABS-Like Black (Accura 7820) Black 7.0 ksi 435 ksi 5%
ABS-Like Translucent/Clear (WaterShed XC 11122) Translucent/Clear 7.9 ksi 421 ksi 6%
MicroFine™ (Gray and Green) Gray or Green 8.7 ksi 377 ksi 8%
PP-Like Translucent White (Somos 9120) Translucent/White 5.0 ksi 232 ksi 25%
PC-Like Translucent/Clear (Accura 60) Translucent/Clear 10.8 ksi 508 ksi 7%
PC-Like Advanced High Temp (Accura 5530) Translucent/Amber 6.5 ksi 566 ksi 1.5%
Ceramic-Like Advanced HighTemp (PerFORM) White 10.9 ksi 1,523 ksi 1%
True Silicone Translucent White 0.711 ksi n/a >1,000%
Material Color Tensile Strength Tensile Modulus Elongation
ABS-Like White (Accura Xtreme White 200) White 54.47 MPa 3300 MPa 9%
ABS-Like Gray (Accura Xtreme Gray) Gray 39.98 MPa 2000 MPa 9%
ABS-Like Black (RenShape SL7820) Black 48.26 MPa 3000 MPa 5%
ABS-Like Translucent/Clear (WaterShed XC 11122) Translucent/Clear 54.47 MPa 2600 MPa 6%
MicroFine™ (Gray and Green) Gray or Green 59.98 MPa 2600 MPa 8%
PP-Like Translucent White (Somos 9120) Translucent/White 34.47 MPa 1600 MPa 25%
PC-Like Translucent/Clear (Accura 60) Translucent/Clear 74.46 MPa 3503 MPa 7%
PC-Like Advanced High Temp (Accura 5530) Translucent/Amber 44.81 MPa 3902 MPa 1.5%
Ceramic-Like Advanced HighTemp (PerFORM) White 75.15 MPa 10,500 MPa 1%
True Silicone Translucent White 4.9 MPa n/a >1,000%

*Properties listed are based on thermal cure

These values are estimates and can vary based on several factors, including machine settings and process parameters. As such, the provided information is not guaranteed or certified. For critical performance applications, we recommend conducting independent lab testing of the additive materials or the final parts.

Surface Finish Options for SLA Parts

Unfinished Dots, or standing “nibs,” remain evident on the bottom of the part from the support structure remnants. Good for when fast lead times are required or cost is a factor.
Natural Supported surfaces are sanded down to eliminate the support nibs.
Standard Supported surfaces are sanded, and the entire part is finely blasted for a consistent look. Note that the layers are still present.
Custom Soft-touch paint, clear part finishing, painting, masking, color matching, decals/graphic, and texture finishes are available.

Material: ABS-like Translucent/Clear

Finish: Unfinished

Material: ABS-like Translucent/Clear

Finish: Standard

Material: ABS-like Translucent/Clear

Finish: Natural

Material: ABS-like Translucent/Clear

Finish: Custom

Material: MicroFine Gray™

Finish: Unfinished

Material: MicroFine Gray™

Finish: Standard

Material: MicroFine Gray™

Finish: Natural

Material: MicroFine Gray™

Finish: Custom

Custom Finishing Options

Custom finishing combines expertise in science, technology, and artistry to meet your precise requirements. Available finishes include:

  • Soft-touch coating
  • Transparent part finishing
  • Painted finishes
  • Masking
  • Color matching
  • Decals and graphics
  • Textured surfaces

Metal Plating

Our metal-plating service for SLA involves coating a ceramic-filled PC-like material (Somos PerFORM) with a layer of nickel, giving parts the appearance, texture, and durability of metal, but without the added weight. This combination of the material’s inherent strength, rigidity, and heat resistance, along with the nickel plating, enhances the part’s strength, stiffness, impact resistance, and thermal stability to levels that were previously unachievable with standard SLA materials.

Microfluidics

Our microfluidic fabrication process is an enhanced version of high-resolution SLA that utilizes a clear ABS-like material (WaterShed XC 11122). These parts are resistant to water and humidity, making them ideal for applications such as lenses and flow-visualization models.

Our SLA 3D Printers

Our stereolithography (SLA) machines include Vipers, ProJets, and iPros. In high-resolution mode, Vipers and ProJets can produce parts with exceptionally fine features and sharp details, while in normal-resolution mode, they efficiently manufacture cost-effective parts at a faster pace.

iPros, on the other hand, offer an impressive build volume of 29 in. × 25 in. × 21 in. (736mm × 635mm × 533mm) while still maintaining the ability to create highly detailed components with precision.

Why Choose SLA?

Stereolithography (SLA) is an advanced additive manufacturing technique capable of producing 3D-printed parts with intricate details, high precision, and exceptionally smooth surface finishes.

How SLA 3D Printing Works

The SLA process starts with the machine using an ultraviolet laser to trace and solidify layers of support structures, followed by the part itself, on the surface of a liquid thermoset resin. Once a layer is formed, the build platform lowers, and a recoating bar spreads a fresh layer of resin across the surface. This layering process continues until the entire part is completed.

After printing, the parts are removed from the machine and taken to a lab, where solvents are used to clean off any excess resin. Once fully cleaned, the support structures are manually detached. The parts then undergo a UV-curing cycle to ensure complete solidification of the outer surfaces. Finally, any required custom or customer-specified finishing touches are applied. To maintain quality, SLA parts should be stored with minimal exposure to UV light and humidity to prevent degradation.

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