UV Curing calculator

UV Adhesive Cure Time Calculator

UV adhesive data sheets typically quote a surface-cure dose; the depth-of-cure dose for a real bondline is 2–4× higher and the irradiance reaching the bondline is lower than the irradiance at the lamp face. This calculator lets an assembly engineer enter the bondline dose target, the irradiance measured at the joint, and a depth-of-cure margin to get a defensible cure time setpoint that won't leave the inside of the bead green.

What this calculator does

  • Estimate cure time for a UV adhesive bondline at a given irradiance — including the depth-of-cure penalty for thick or pigmented beads.
  • Use it on assembly cells where UV adhesive is the cycle-driver and you need a defensible bond cure setpoint, not the data sheet's surface-cure number.
  • Reports the seconds the joint needs under the lamp to reach full bondline cure, padded by a depth-of-cure margin.

Formula used

  • Base cure time (sec) = bondline dose target ÷ irradiance at joint
  • Recommended cure time = base cure time × (1 + process margin)

Inputs explained

  • Bondline dose target: Depth-of-cure dose from the adhesive vendor — typically 2–4× the surface-cure number on the front of the data sheet.
  • Irradiance at the joint: Measured at the bondline location — through any fixture / substrate the light has to pass through.
  • Depth-of-cure / process margin: Cushion for bead-thickness variation, pigment loading, and adhesive batch variation; 25–40% typical.

How to use the result

  • Use it on every UV adhesive assembly cell when introducing a new product, after an adhesive lot change, or when bondline tests show low strength despite a passing surface-cure check.
  • Doesn't model substrate UV transmission. If the light has to pass through a tinted, frosted, or coated substrate, irradiance at the joint may be 30–80% lower than open-beam — measure with the actual stackup, not at the lamp face. Also assumes the adhesive isn't oxygen-inhibited at the bondline (most aren't, since they're between substrates, but check exposed fillets).

Common questions

  • Why is my cure time longer than the data sheet says? Two reasons usually: you're using surface-cure dose where you should be using bondline / depth-of-cure dose, and the irradiance at the joint is lower than what the data sheet assumed. Both push real cure time up by 2–4×. Pull the depth-of-cure column from the data sheet and re-measure irradiance through the actual substrate.
  • How do I measure irradiance through a substrate? Place a thin radiometer puck on top of a sacrificial part of the substrate at the joint location, with the lamp at production setpoint. Read mW/cm². Compare to a reading without the substrate to get the substrate's UV transmission percent — useful for any future joint with the same material.
  • What process margin should I use? 25–30% on consistent assemblies with controlled bead width; 40–50% on hand-dispensed adhesive or anywhere bead thickness varies shift to shift. Margin here protects against the cure-time-to-thickness relationship that bites first when bead thickness creeps up.
  • Can I use this for spot-cure pens? Yes — same math. Spot cure devices typically deliver high irradiance (1–10 W/cm² = 1,000–10,000 mW/cm²) so cure times come out short. Make sure your dose target uses the depth-of-cure number for the bond geometry, not the spot-cure tip exposure.

Last reviewed 2026-05-12.