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How to Optimize Your Flash Curing

(August/September 2017) posted on Tue Sep 12, 2017

Learn ways to increase your production while reducing cost, heat, and wasted energy.

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By Mark A. Coudray

Panel flashes are still in common use today, mostly with manual printers and entry-level automatic presses. They are operated either in a continuous cycle, with the power always on, or they have proportional timers that surge the unit with power on a 15- to 30-second cycle. Either way, they are either power on or power off. (While it’s possible to reduce the amount of current through the proportional timers, it’s not commonly done with this heat source.)

Blackbody panels produce uniform IR heat when energized. The amount of energy (or radiance) they emit is expressed in watts of energy per unit of area (W/sq in. or J/sq cm), sometimes called the watt density of the emitter. The higher the watt density, the shorter the time needed to cure. Think of high watt density as the difference between a match and a blowtorch.

The theory of the energy distribution of a blackbody surface was developed by German theoretical physicist Max Planck in 1900. Planck’s law describes the spectral energy density of electromagnetic radiation (wavelength of light) a blackbody emits at a given temperature. In order for the temperature of a surface to be raised, it must absorb this radiant energy.

Planck defined a blackbody as a surface that completely absorbs all incident radiation. It also emits radiation at the maximum possible monochromatic intensity in all directions and at all wavelengths. This means that all colors have the same intensity of radiance. In other words, the emitted energy is color-blind – all colors absorb equally.

Planck further established that the radiance at each IR wavelength is the maximum amount possible for a given temperature. If we used an IR spectrometer to measure this emitted energy and plotted the result, it would follow the Planck distribution. Planck hypothesized that energy can be absorbed or emitted only in fixed units of photons of energy. This absorption does not change and is known as Planck’s constant.

What does this mean for us? The key takeaway is that IR energy emitted by a blackbody will have no visible color, and so all colors will absorb the energy equally. White will cure at the same rate as black. This is particularly attractive when you have heat-sensitive materials like tri-blends and you want all ink colors to gel at the same rate without overheating the yarn.


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