Why does duty not reduce heat on the part?

The part is only there while the lamp is on. Duty says what fraction of the hour the lamp emits; a part passing underneath takes the full flux for its whole pass regardless.

What IR fraction should I use?

It depends more on the reflector than the lamp. A dichroic reflector passes infrared out the back and reflects UV forward, so far less heat reaches the part; a plain aluminum reflector sends both.

How do I turn this flux into a temperature?

You cannot from this page alone. Temperature needs thermal mass, conductivity, dwell time and what the part sits on; a film on a chilled roll behaves very differently.

My substrate distorts but the cure is fine.

Attack the heat, not the dose. A dichroic reflector, a filter, greater lamp height or more spread area all cut flux while leaving UV. Slowing the line does the opposite.

UV Curing calculator

UV Heat Load Calculator: Peak Flux

Separate the heat a part sees under the lamp from the average that warms the room. Enter lamp input, the IR fraction reaching the part, the duty fraction and the irradiated area.

What this calculator does

Peak heat flux a substrate sees under the lamp, separated from the hourly average that loads the room.

Formula used

Heat to the part (kW) = lamp input × IR fraction
Peak heat flux = heat to the part × 3412.142 ÷ irradiated area
Average heat to the part = heat to the part × duty fraction
Average heat load = average heat × 3412.142
Applied fraction × duty = IR fraction × duty fraction

Inputs explained

Lamp Electrical Input Power: Electrical input at the power setting actually run.
IR Fraction Reaching the Part: Share of input power arriving at the part as heat.
Lamp Duty Fraction: Fraction of the hour the lamp emits onto parts.
Irradiated Area: Illuminated width times cure-zone length, in square feet.

How to use the result

Best suited to checking a heat-sensitive substrate before buying, sizing ventilation and room cooling for a cell, deciding between dichroic and standard reflectors.
Gives a flux, not a temperature; reaching a temperature needs thermal mass, dwell and backing. Assumes uniform distribution; real profiles peak in the middle, so the hottest point is hotter. Ignores exhaust heat removal and cumulative heating over multiple passes.

Common questions

Why does duty not reduce heat on the part? The part is only there while the lamp is on. Duty says what fraction of the hour the lamp emits; a part passing underneath takes the full flux for its whole pass regardless.
What IR fraction should I use? It depends more on the reflector than the lamp. A dichroic reflector passes infrared out the back and reflects UV forward, so far less heat reaches the part; a plain aluminum reflector sends both.
How do I turn this flux into a temperature? You cannot from this page alone. Temperature needs thermal mass, conductivity, dwell time and what the part sits on; a film on a chilled roll behaves very differently.
My substrate distorts but the cure is fine. Attack the heat, not the dose. A dichroic reflector, a filter, greater lamp height or more spread area all cut flux while leaving UV. Slowing the line does the opposite.

Last reviewed 2026-10-01.