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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

Medium-wave IR lamps are much more expensive than the short-wave tubes used in the least expensive quartz flash units. Short-range bulbs are much more prone to selective color reflectance, meaning (no surprise) that white reflects and black absorbs. The difference is that white can reflect up to 95 percent of the energy while black can absorb up to 80 percent of it. In other words, it would take 16 times more energy to cure the white. Obviously, the black ink or the garment would be toast long before the white ink gels.

This is a very important concept. The whiter or yellower the light looks, the more reflective the IR will be to different colors. This means that if you see white or yellow light from your lamps, most of the energy is being reflected at the substrate surface by the ink.

Ideally, we would like to combine the radiance of a blackbody panel with the responsiveness of a quartz lamp. We can’t have both, so we compromise. Medium-wave and fast medium-wave IR provide good absorption across colors. There is some color sensitivity, but it is tolerable. The frequency of medium-wave IR is between 3.4 (1100 degrees F) and 3.9 (900 degrees F) microns. The higher the frequency, the lower the temperature and the less it reflects color. (See Figure 3.)

FIGURE 3 The ideal flash temperature to generate the medium-wave IR that works across the range of colors is between 900 and 1100 degrees F. Narrower wavelengths below 3.4 microns generate more heat that will be more reflective.

An item of note here: The most efficient transfer of radiant heat, in a color-blind mode, is around 900 degrees F. This is one of the reasons that the temperature on blackbody panels is set so much higher than what plastisol cures at, and it’s a source of confusion for many printers.

Higher temperature settings will not help you. In fact, the higher the temperature, the more reflective the surface becomes, and you actually lose efficiency. Setting the unit below 900 degrees F reduces the emitted energy, so the only way to speed up the transfer is to lower the distance between the panel and the surface, as we shall see.


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