ForMatter/Processes/additive/SLA 3D Printing (Stereolithography)
proc_sla_3d_printing

SLA 3D Printing (Stereolithography)

additive · stereolithography, vat photopolymerization, MSLA, DLP

A laser or screen of UV light hardens liquid resin layer by layer. Smoother surface than filament prints, finer detail, brittle until post-cured. The technology behind dental aligners, jewelry casting masters, miniatures.

Vat photopolymerization. Original SLA uses a moving UV laser tracing each layer; modern desktop variants (MSLA / DLP) use an LCD or projector to flash an entire layer at once. Layer heights routinely 0.025–0.1 mm. Parts require IPA wash + UV post-cure.

Scale & Tolerance

  • scale (mm)0.5 – 800
  • tolerance (mm)0.05
  • skillintermediate — supports require thought; resin handling needs gloves and ventilation
  • min skillbeginner
  • wheredesktopschool shopprofessional
  • costlow to moderate per part; capital cost low to moderate

Equipment

  • school_shopyes — Formlabs Form 3, Anycubic Photon, Elegoo Saturn desktop MSLA
  • professionalFormlabs Form 3L large-format, 3D Systems ProJet
  • industrialEnvisionTEC, 3D Systems large-frame stereolithography

Environmental

  • energy_uselow
  • waste_streamuncured resin (hazardous), IPA waste, support structures — uncured resin must NOT enter drains
  • consumablesresin, IPA, build platform film, FEP sheet

Cost over volume

1101001k10k100k1M0.00010.0010.010.1110100100010000100000units (log scale)total cost (relative, log scale)

Numbers are relative ratios, not dollars. The crossover point matters more than the magnitude. Anchored to injection molding + ABS = 1.0.

Trade-offs

constraints · what is lost · what is gained
Clear Photopolymer Resin (UV-cure SLA / DLP / MSLA)
  • constraints
    • min wall thickness ~0.6 mm at 0.05 mm layer height
    • support structures required for any overhang >30°; supports leave witness marks
    • trapped-volume / suction-cup geometries pull the build platform off mid-print
    • near-isotropic (better than FDM Z-strength) but layer lines still visible at low oblique angles
  • what is lost
    • support contact dimples on the part underside until sanded
    • post-cure brittleness — most photopolymer resins lose impact strength after UV cure
    • yellowing under prolonged UV exposure unless tinted
  • what is gained
    • the canonical investment-casting master process for jewelry and dentistry
    • feature resolution down to ~50 µm — finer than FDM by an order of magnitude
    • transparent and translucent resins for fluidic prototypes and optical mock-ups
    • tooling-free runs of detailed jewelry, miniatures, and orthodontic aligners

Plain language. Neutral framing — perfection is contextual, defined by use. Cf. Winchester, The Perfectionists (HarperCollins, 2018).

Second life

reversibilityzero — UV-cured photopolymer is irreversible.
output recyclabilityno
waste streams
  • uncured resin in vat (recovered and re-used until cloudy)
  • support-structure scrap
  • isopropyl-alcohol wash waste (regulated)
  • failed-print scrap (cured photopolymer is landfilled)
repair compatible withproc_adhesive_bonding

Formlabs / 3D Systems / Stratasys SLA technical literature; ASTM ISO/ASTM 52900.

In the collection

Citations

  • book · Lefteri, *Making It: Manufacturing Techniques for Product Design*, 2nd ed. (Laurence King, 2012), 'Stereolithography (SLA)' p. 246.

Further reading