The Balancing Act: Ink vs. Glass in IR Annealing
Here is the problem we deal with when you’re tempering screen-printed glass: physics doesn’t always play nice. You need the glass to hit its softening point to get rid of that internal stress, but you can’t just blast it with heat. If you do, your ink will burn or peel right off the surface. It’s a tightrope walk. We use short-wave infrared (IR) lamps to solve this. Why? Because they punch through the glass surface way faster than standard convection heat. Getting the heat just right The goal is simple: get the glass hot enough to temper, but don’t cook the print. If your heat density is too high or the glass sits under the lamps for too long, the ink starts to boil. It’s a mess. We spend a lot of time dialing in the wattage and the spacing of the lamps. We want the heat to soak into the glass substrate while keeping the ink’s surface temperature in a safe zone. Choosing the right gear We usually go with quartz halogen lamps. They ramp up fast, which keeps things moving. But the real secret is in the power zones. You can’t just treat the whole tunnel the same. By tweaking the voltage across different sections, we can fight the heat loss that happens at the edges of the glass sheet. Without that, you get “cold spots.” And cold spots mean uneven tempering, which usually ends with the glass shattering during the quench. Not a great day at the office. The trade-off Now, you might think, “Why not just crank up the wattage for faster cycles?” Well, there’s a catch. When you push that much power into the lamps, the machine frame starts to feel it. If you haven’t got your cooling fans and ventilation dialed in to move that hot air, you’re asking for trouble. You’ll end up warping your conveyor rails or frying your lamp connectors. It all comes down to alignment. If those lamps are even slightly off, you get hot spots. That means ruined prints and weak glass. Get the angle right, and everything just works.