Resin 3D Print Exposure Time Calculator
Estimates the per-layer UV exposure time for MSLA/LCD resin printers based on layer thickness, UV power, and screen age. Use it when dialing in a new resin or replacing the LCD screen.
About this calculator
In MSLA resin printing, each layer is cured by flooding it with UV light through an LCD mask. The required exposure time grows with layer thickness (more resin depth to cure), falls with UV power (stronger light cures faster), and must increase as the LCD ages because the screen transmits progressively less UV over time. The formula is: exposureTime = (layerThickness / 0.05) × (50 / uvPower) × (screenAge / 100). The first term normalises thickness to a 0.05 mm reference — a 0.10 mm layer needs twice the base time. The second term normalises power to a 50 W reference — a 25 W lamp needs twice as long. The third term applies a linear degradation factor so a screen at 80 % transmission requires 25 % more exposure than a new screen. Multiply the result by a resin-type coefficient for opaque, pigmented, or water-washable resins.
How to use
Example: layer thickness 0.05 mm, UV power 40 W, screen at 90 % age factor. 1. Thickness term = 0.05 / 0.05 = 1.0 2. Power term = 50 / 40 = 1.25 3. Screen-age term = 90 / 100 = 0.90 4. exposureTime = 1.0 × 1.25 × 0.90 = 1.125 seconds Set your slicer to 1.1–1.2 s per normal layer. Bottom layers typically need 8–12× this value (9–13 s) for a solid raft.
Frequently asked questions
How does layer thickness affect resin exposure time in MSLA printing?
Thicker layers require longer exposure because UV light must penetrate deeper into the liquid resin to fully polymerise it all the way to the previous layer. The relationship is approximately linear for small thickness changes around the standard 0.05 mm range — doubling the thickness roughly doubles the needed time. Going too thick risks under-curing the bottom of the layer, causing delamination or brittle parts. Most resins work well between 0.025 mm and 0.10 mm, with 0.05 mm being the standard sweet spot.
Why does an aging LCD screen require longer exposure times for resin printing?
LCD screens used as photomasks in MSLA printers degrade with UV exposure over time — the liquid crystal layer and polarising films gradually lose transparency to UV wavelengths. This means less UV energy actually reaches the resin per second, so you need to expose for longer to deliver the same total energy dose. Screen life is typically rated in hours (often 500–2000 hours for monochrome screens). Tracking screen age in hours and recalibrating exposure every few hundred hours keeps print quality consistent.
What is the difference between normal layer exposure time and bottom layer exposure time in resin printing?
Bottom layers (the first 4–8 layers) use a much longer exposure — typically 8–12 times the normal layer time — to create an aggressively bonded foundation on the build plate. This over-cure ensures the print survives the peel forces that occur as the plate lifts after each layer. Normal layers use a shorter, optimised time that balances full cure with minimising bleed (light that cures resin outside the intended pixel area). If bottom exposure is too short, the print detaches mid-build; if too long, it fuses to the FEP film.