• Introduction

    Stereolithography, otherwise known as SLA, is a 3D printing method which uses a laser to cure photopolymer resin layer by layer. SLA is famously known for producing smooth parts with extreme fine detail and high accuracy levels. Stereolithography uses a vat of liquid UV-curable photopolymer resin and also includes a UV laser to build 3D parts layer by layer. As each layer progresses, the laser beam carefully traces a part of the cross-section pattern on the surface of the liquid resin. UV laser light cures and solidifies patterns once it’s been exposed. Once a pattern has been traced, the elevator platform descends a single layer thickness. The thickness is usually 0.05 mm-0.15 mm (0.002 in.-0.006i= in.). After, a fresh material is re-coated as the resin-filled blade sweeps across the part section.

    Through following these Stereolithography (SLA) 3D printing design guidelines your parts should come out as intended, but for additional questions and complex problems be sure to reach out to a member of our engineering team.

  • Technical Specifications

    FeatureDescription
    Supported Walls Walls attached to structures on a minimum of two sides
     Smaller chance of the product warping
     Suggested design = 0.4 mm  thick
    Unsupported Walls Walls attached to the print on fewer than two side
     Walls have higher chance of warping/detaching from the print
     0.6 mm thickness required
    Overhangs Overhangs only occur when your model is printed without substantial internal/external support structures
    Engraved Details (Including text) Details must be 0.4 mm wide and 0.4 mm thick
    Embossed Details (Including text) Required height of 0.1 mm above surface
     This ensures details become visible
    Horizontal Bridges Wider bridges must be kept shorter (21 mm) than thin bridges
    Holes X, Y, Z axis can close off during printing
     To prevent this, have hole diameter less than 0.5 mm
    Connections/Moving Parts 0.5 space separating moving parts
     0.2 mm space for assembly connections
     0.1 mm space provides close knitted fit
    Minimum Features Recommended minimum = 0.8 mm
  • Resolution

    Compared to FDM, SLA can reach a higher resolution as it uses a laser to solidify the material. When printing SLA in the horizontal/XY-direction, the laser spot and size can range from 30-140 microns. Note that the smallest feature size can’t be less than what the laser spot size is.

     

     

     

  • Hollowing And Cupping

    SLA machines have the capability to print a solid and dense 3D printed model. Hollowing the model can reduce the  required amount of material and it can also reduce the print time significantly. When printing, ensure the walls located on the hollowed print are a minimum of 2 mm thick. Failure becomes less likely during printing this way. Drainage holes are necessary when printing a hollow part to prevent uncured resin from getting trapped inside the final part.  Pressure within the unsecured resin creates imbalances within the hollow chamber and will cause ‘cupping’ Cracks and holes spreSomos18420 SLA 3D printing materialad throughout the part and will cause ultimate failure. Part explosion is also a possibility if not corrected/ The minimum requirement of drain holes are 3.5 mm in diameter, and a minimum of one hole must be involved per hollow section.

  • Materials

    SLA Accura Xtreme 3 3D PrintingAccura Xtreme

     

     

     

     

    accura clearvue 3D Printing materialAccura ClearVue

     

     

     

    accura-bluestone

    Accura Bluestone

     

     

     

     

    Accura 25 3D Printed Vent

      Accura 25

     

     

     

     

     

    Accura55 SLA 3D Printing

    Accura 55

     

     

     

     

     

    3D systems Somos Watershed XC 11122 SLA 3D Printing material

    Somos Watershed 11122

     

     

  • Restrictions

    Print Volume
    Take into consideration that SLA printers have a significantly smaller build volume compared to FDM printers (besides commercial machines). The build volume when using  The traditional SLA desktop printer, Formlabs Form 2, have a build volume of 145 mm x 145 mm x 175 mm. Meanwhile, the common FDM desktop printer, the Ultimaker 2+, offers a build volume of 223 mm x 223 mm x 205 mm. Another thing to keep in mind when printing with SLA is that if the print geometries exceed the printer capacity, they can be printed in smaller sections and then be assembled. Best practices when bonding SLA printed parts together is a 5-30 minute epoxy.

    Material Properties
    If you’re looking to produce functional parts that are subjected to loads, it’s best to stray away from SLA parts. SLA resins tend to be brittle and not as reliable compared to other 3D materials. Over a certain amount of time, these SLA parts tend to experience creep. Curing in a UV chamber is needed for most SLA printed parts.

    SLA vs. FDM cost
    Using SLA resin is higher in cost when comparing it to FDM filament. However, SLA holds the potential to print details with more complex details, while other 3D printing options, don’t hold that title.

  • Common Resins

    Resin TypeDescriptionApplication
    Standard Resin Used for generic printing
     High detailed finish
     Resolution less than 25 microns
     Used to achieve high   detail prototyping
     Works with models that     are not functional
    Engineering Resins Resin manufacturers have been simulating engineering plastics
     ABS/polypropylene-like/flexible/high temperature resins
     Resins have stronger engineering properties
     Durable
     Flexible
     Used in high temperature applications
    Dental Resins Often used for general orthodontics
     Class 1/2 bio-compatible resin released to allow SLA technology to create surgical guides
     Highly precise and durable
     Dental applications
    Castable Specialized in fine detail
     Delicate feature printing
     Designed for direct investment casting
     Minimum feature size is 0.2 mm
     Jewllery
     Fine detail models
     Investment casting applications

     

  • Post-Processing

    SLA has a wide range of surfaces finished which are determined by cost and application. Details with features as small as 0.3 mm are possible when using SLA printers. However one of the biggest issues faced when using an SLA printer is that prints are made extremely small, therefore most prints should be put on an angle. Support structures are necessary when SLA printing

    ProcessDescriptionProsCons
    Basic Support Removal Support structure cut from the model
     Results in bumpy surface
     100% control of finish
     Drilling achieves vertical hole diameter accuracy
     Suitable for all SLA resins
     High speed
     Moderate tolerance
     Not appealing
     Required amount of skills needed to get a clean finish
    Sanded Support Nibs Made for flat surfaces Surface accuracy
     Matte finishes hide imperfections
     Suitable for all SLA resins
     High speed
     Uneven surfaces
     Not aesthetically  pleasing
    Wet Sanded Smoothest finishes
     Build lines require sanding
     Finish is cheap using high grade sandpaper
     Smooth finish
     Useful for complex geometries
     Ideal surface preparation for   painting
     Accuracy is low on supported side
     Mixing sand and water could lead to spots on your print
    Mineral Oil Finish Process relates to wet sanded finish, except oil layer is added after sanding process
     Mineral oil hides white spots on finsih
     Finish is made best for mechanical parts
     Semi transparent finish for clear resins
     Suitable for all SLA resins
     Paint doesn’t adapt to  finish surface properly
    Spray Paint (clear UV protective acrylic) Spray painting makes layer lines invisible
     Varnish protects the model from   yellowing and post curing by   limiting UV exposure
     Clear finish
     Offers UV protection
     Suitable for all SLA   resins
     ‘Orange peel effect’   on surfaces
     Increases dimensions
     Not made for moving   parts
    Polished-Clear Transparent Finish Grit levels of sandpaper are used to sand the surface
     Polishing compound is then sued to polish the surface
     This leaves the most clear surface   possible, but can be time   consuming
     Finish is made for simple shapes
     Finish is as clear as glass
     Smooth surface
     Intense labour involved
     Not attainable without complex geometries
     Only suitable for clear resin