Getting resin exposure right is the single biggest factor in MSLA print success. This tool gives a sensible starting point for both normal layers and the all-important bottom layers, scaled to your layer height and printer’s LED power, so your first exposure test lands close.
How it works
Curing resin is an energy problem: each layer needs a certain UV dose, and exposure time is that dose divided by the LED’s power.
exposure = base × (layer_height / 0.05) × (reference_power / LED_power)- Layer height sets the cure depth required, so time scales with it.
- LED power divides the time — a brighter array cures the same layer faster.
- The base resin value captures how reactive each resin chemistry is (flexible and tough resins are slower than standard model resin).
Because real printers and resin batches vary, the tool reports a roughly ±25% window around the point estimate. You then print a calibration matrix and pick the value that gives crisp detail without bloating.
Bottom layers are handled separately. They are exposed many times longer (the multiplier) to weld the print to the plate, then transition layers fade that long time down to the normal time over several layers to avoid a hard seam.
Reading the symptoms: over vs under-exposure
Knowing which direction your current settings sit tells you exactly which number to adjust:
Signs of over-exposure:
- Small holes and gaps in the model are filled in or too small
- Lettering and fine detail is thickened or blurry
- Supports are difficult to remove and leave large scars
- “Elephant foot” — the first few model layers flare outward wider than the model
Signs of under-exposure:
- Layers delaminate or parts fail mid-print
- The surface feels soft, rubbery or tacky after post-cure
- Parts warp, especially thin horizontal spans
- The print sticks to the FEP film rather than the build plate
If you see elephant foot on model layers (not just the base), the normal-layer exposure is too high even though bottom layers are fine — reduce normal time in 0.5-second steps. If you are getting FEP adhesion and failures, the problem is usually normal-layer time too low, not base-layer.
Base layers and transition layers explained
The bottom (base) layers serve one purpose: strong mechanical adhesion to the build plate. They are deliberately over-cured — typically 3–16× the normal time — to maximise the bond. This over-curing means they are dimensionally inaccurate and should always sit below the actual model geometry.
Transition (or fade) layers step the exposure time down from base to normal over a user-defined number of layers. Without a transition, you get a hard step: one layer is exposed for 40 seconds, the next for 2 seconds. That sharp change can cause a visible seam in the geometry and sometimes delamination. With 5 transition layers, the time steps down gradually: 40 → 32 → 24 → 16 → 8 → 2 seconds. The exact count depends on the resin and the step size; 4–8 transition layers is a typical starting range.
Tips and notes
- Always validate with a printed exposure test (a stepped wedge or a calibration model such as a validation matrix) rather than trusting any single number.
- Colder resin cures slower — warm the resin and room to around 25 °C for consistent results.
- If supports tear off the plate, increase base-layer count or base exposure before touching normal-layer time.
- If small holes close up or text fills in, you are over-exposing the normal layers; reduce the time in small steps.
- Pigmented resins (especially white and grey) cure slower than clear or translucent resins — add 10–20% to the exposure estimate as a starting point.
- Resin batches from the same brand can vary; when a new bottle arrives, run a fresh calibration even if you know the settings for that brand.