What is Stereolithography (SLA)?

Stereolithography (SLA) Production Printers build accurate parts directly from 3D CAD data without tooling by converting liquid plastic (photopolymer) into solid cross-sections using an ultraviolet laser. The part is created layer by layer, with each resin layer built on top of the next until the part is complete. This process is also known as photopolymerization.

When an SLA part is complete, it is cleaned in a solvent solution to remove wet resin remaining on the part surface. Afterward, the part is put in a UV oven to cure it, completing the resin printing process. 

3D Systems SLA Production 3D Printers offer high throughput, build size up to 1524 mm, unmatched part resolution and accuracy, and a wide range of print materials. No other additive manufacturing process addresses a wider range of applications, including the most demanding rapid manufacturing applications for highly accurate and durable prototypes of all shapes.

SLA technology is extremely versatile and it can be used when precision is the overall priority and where form, fit and assembly are critical. The tolerances on an SLA part are typically less than .05 mm, and this technology offers the smoothest surface finish of any additive manufacturing process. Considering the level of quality SLA can achieve, it’s particularly useful for creating highly precise 3D printed casting patterns from small to very large scale, quickly and inexpensively.

SLA allows manufacturers to save time on highly precise parts, especially when you require a number of functional prototypes or a quick single casting pattern. SLA can create parts that will have a smooth finish right out of the printer, which makes them easier to polish, paint and finish if necessary, and ideal for wind tunnel testing and similar applications. 

Stereolithography also brings painstaking accuracy without the painstaking time. Because of SLA’s speed and precision, prototypes are easy to make and faithful to the final design, which means you can identify design flaws, collisions and potential mass-manufacturing hurdles before production begins. For low- to mid-volume parts normally machined from polypropylene or ABS, 3D Systems SLA materials provide comparable characteristics and don’t require slow, expensive retooling for customization or in the event a tooling change is required. In addition, SLA allows for lower material costs, as the unused resin stays in the vat for future projects, and it creates parts that are more flawless overall.

SLA materials are wide-ranging in mechanical properties and offer a wide array of applications for parts requiring ABS or polypropylene-like characteristics such as snap-fit assemblies, automotive styling components and master patterns.

SLA materials available for higher-temperature applications and clear materials are available with polycarbonate-like properties. Biocompatible materials are available for a wide range of medical applications, such as surgical tools, dental appliances and hearing aids. Other materials are specifically formulated for patterns, offering low ash creation and high accuracy while also being expendable.

Common SLA materials include:

• Standard resin. Great for prototypes with detailed surface finishes.
• Engineering resin. Ideal for high-temperature applications due to toughness and flexibility.
• Castable resin. Best for investment casting applications due to capacity for fine details.
• Dental resin. Highly durable and precise for dental applications.

3D Systems offers a wide range of stereolithography materials, including:

Accura® 55 (See material specifications)

This is a strong, rigid plastic SLA material that simulates and replaces CNC machined white ABS articles. It is ideal for functional assemblies and short-run production parts.

Accura® Xtreme™ White 200 (See materials specifications)

This ultra-tough white plastic can replace CNC machined polypropylene and ABS articles. This ABS-like material is durable enough to resist breakage and handle challenging functional assemblies. It is ideal for snap fits, assemblies, demanding applications and master patterns for vacuum casting.

Accura® 25 (See materials specifications)

Flexible plastic to simulate and replace CNC-machined white polypropylene articles. • Flexible • Snap fit assemblies • Master patterns for vacuum casting • Durable functional prototypes

Accura® 60 (See materials specification)

• Clear plastic for quickly producing rigid and strong parts.
• Clear and transparent • Rigid and strong • Great for investment casting patterns • Headlamps, bottles and transparent assemblies

Accura® PEAK™ (See materials specification)

• Stiff plastic material for heat-resistant components.
• High heat resistance • Very high rigidity and stiffness • Excellent humidity/moisture resistance

Accura Phoenix SLA (see materials specification)

Thermally resistant plastic with exceptional clarity that improves viewing of hot fluid flow in complex automotive parts as well as viewing of internal structures in assembly work.

See a complete list of our available SLA materials.

Stereolithography is ideal for high-accuracy small parts that require smooth surface finishes, such as prototypes and models.

With the 3D Sprint print preparation software that is supplied at no charge for all new SLA printer sales, engineers and product designers can quickly and easily deliver a perfectly printable design into the additive platform.

SLA Design Best Practices

Here are some best practices for preparing and executing an SLA design into print.

• When you orient a part for SLA printing, focus on reducing the area along the Z-axis. A reduction in the support across the Z-axis cross section area will require more support to be added to your model. The right supports will be critical to successful part creation.
• If a good surface finish is necessary, you must orient the part so that the surface material does not touch the part. This is typically done by placing it face-up on the supports.
• Supported walls will reduce chance of warping and should be a minimum of .4 mm thick.
• Unsupported walls have a higher chance of warping or detaching from the print and should be at least .6 mm thick.
• Any recessed or imprinted features may fuse with the rest of the model and become invisible if they are too small. To prevent this:
  • Embossed details must be at least .1 mm above the surface of the print.
  • Engraved details must be at least .4 mm wide and .4 mm thick.
• Holes in the x, y, and z axes that are less than .5 mm in diameter may close off during printing.
• Always allow .5mm clearance between moving parts, and a .2mm clearance for assembly connections.
• Reduce your print time and materials by hollowing your model. The walls should be at least 2 mm thick so the walls don’t fail during printing.
• The separation phase of printing makes your model highly vulnerable to failure and warping. Ensure a successful print by reducing the forces on your layers when separating your model.