Layer Cure Calculator — Cure Depth & Energy Dose

Cure depth is how deep the UV light polymerises the resin in one exposure. It must be deeper than the layer height so each new layer bonds to the one below. Typically, cure depth should be 1.5-2x the layer height.

The Jacobs equation (Cd = Dp x ln(E/Ec)) describes how deep UV light cures into resin. Dp is the penetration depth (material property), E is the energy dose, and Ec is the critical energy needed to start curing. It is the fundamental equation of SLA printing.

Use the irradiance measured at the build surface, not the LED-array wattage on the spec sheet. On consumer mono-LCD (MSLA) printers the LCD panel absorbs most of the light, so surface irradiance is typically only about 3-8 mW/cm² (around 6 mW/cm² is the threshold where most 405 nm resins begin to gel). DLP machines, which have no masking LCD, run higher at roughly 15-25 mW/cm². Measure yours with a 405 nm UV radiometer placed on the build plate.

Over-curing causes the light to bleed past the intended layer boundary, curing resin that should remain liquid. This results in loss of fine detail, thicker features than designed, and can cause hollow parts to cure solid if the walls are thin.