Stop the Chips: Why We Preheat Glass Before Cutting
Cutting glass is basically just a controlled crash. You’re forcing a fracture. When you hit a cold sheet with a cutting wheel, all that internal tension creates tiny micro-cracks. The problem is, those cracks don’t always go where you want them to. They wander. That’s how you end up with those annoying chips and “blow-outs” on your edges and corners. To fix this, we use infrared (IR) preheating. We’re essentially changing how the glass behaves before the blade even touches it. How the heat actually helps Infrared heaters dive deep into the surface and warm things up fast. This thermal energy relaxes the glass, easing that internal stress. Think of it as softening the mood of the material. When the glass is warm, the surface layer is less stubborn. The fracture line actually sticks to your score mark instead of veering off. It’s a relief. Your scrap pile shrinks, and those frustrating corner chips mostly disappear. Getting the setup right We usually go with short-wave IR lamps. Why? Because they heat up almost instantly. You need a lot of heat in a short amount of time, otherwise, your conveyor belt would have to move at a snail’s pace. But you can’t just crank the heat to a hundred. If you blast it, the glass expands unevenly, and you’ve just created a whole new set of stresses. It’s a balancing act. You have to tweak the wattage and the distance of the lamps to make sure the heat is spread evenly across the whole sheet. The real-world trade-offs Now, this isn’t a “magic button.” Adding preheating means adding another step to your line. Your power bill will go up, and you’ll need a cooling system for the lamp housings so the reflectors don’t warp from the heat. And here’s the tricky part: your conveyor speed has to be steady. If the belt speeds up or slows down, your temperature shifts. You need your IR controllers and your line speed talking to each other in real-time. If you get the temp wrong, you’re not solving the problem—you’re just trading chips for thermal cracks. It takes a bit of tuning, but once it’s dialed in, the difference in quality is obvious.