Dealing with Thermal Shock in Glass Score Line Heating
Here is the reality of working with glass: it doesn’t like sudden changes. If you take a cold piece of glass and hit it with a wall of heat too fast, it’s going to crack. Every time. To get around this, we use shortwave infrared (IR) lamps for “instant tempering” along the score lines. The trick is hitting a very specific spot with heat quickly, without stressing out the rest of the glass. The secret is in how you control the power. You can’t just flip a switch and blast the glass with constant heat. That’s a recipe for disaster. Instead, we pair these lamps with fast-switching controllers—think SCRs or Thyristors. These things are incredibly precise. They let us tweak the power in milliseconds. By curving the wattage up and down, we can manage how the glass expands. If you pick a lamp with too much wattage for your line speed, you’ll end up with “hot spots.” And once you see a hot spot, you’re usually looking at a fracture. What about the gear? We almost always go with quartz halogen tubes. Quartz is great because it can handle insane temperatures while still letting that shortwave radiation pass right through. Honestly, shortwave IR is the only way to get heat to penetrate the surface fast enough to keep a high-speed production line moving. You’ll usually see these using R7s or SK15 connectors. They aren’t fancy, but they’re the industry standard for a reason: they make replacements easy. When a tube finally burns out, you just pop it out and drop a new one in. No need to spend your afternoon rewiring the whole heating bank. The trade-offs you have to consider. High-density heating puts a massive strain on your electrical setup. Sure, cranking up the voltage gives you more heat, but it also beats up the lamp’s electrodes. It’s a balancing act. You have to weigh the power rating of the lamp against how well your cooling system can pull the ambient heat away from the housing. If you ignore the cooling, your tubes are going to die a lot faster than they should.