Learn ways to increase your production while reducing cost, heat, and wasted energy.
The inverse square law states that energy at the surface varies inversely to the change in the distance. (See Figure 5.) The temperature rise is measured by multiplying surface energy by time. It sounds complicated, but it simply means that if you double the distance to the emitter, the amount of energy decreases by a factor of 4. Conversely, if you cut the distance by half, you quadruple the amount of energy at the surface. Put another way: If your flash time is 2 seconds at the current distance, then by halving the distance, your flash time will drop to half a second.
This is a great thing to know if you are using blackbody panels and you want to shorten your flash times. Set the surface temperature to 900 degrees F and then reduce your time according to how much you lower the panel toward the surface.
For quartz tubes with reflectors, however, lowering the distance will create severe temperature variation. You’ll likely burn the material while having uncured ink right next to the scorched areas. Increasing the distance with a quartz flash will also have a compound effect on energy loss due to the now-diffused reflector.
Pulling It All Together
So with a better understanding of how IR heat behaves, how do you put the pieces together? The key to high-production, efficient flashing is knowing how to direct and sequence the transfer of heat.
Whether you are using plastisol, water-based, or silicone ink, the goal of flashing is to temporarily set the ink so it does not transfer to the subsequent screens. Here, physics again come into play. Ink transfer happens because the printed ink film splits between the substrate surface and the backside of the following screens. The adhesive force of the ink binding to these surfaces is greater than the cohesive force holding the ink film together, so it splits in the middle, with some ink transferring from the substrate to the back of the next screen.
Our goal is to gel the ink layer to the point where the cohesive force is greater than the adhesive force, hence no transfer. We can do several things to help accomplish this.
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