Stopping Quartz Glass from Cracking During Tempering
Working with quartz glass is a bit of a tightrope walk. You have to get the temperature ramps exactly right. If you rush the heating or let it cool down too fast, you’re going to end up with stress fractures. It’s frustrating and wasteful. To handle that “instant tempering” phase, we lean on shortwave infrared (IR) lamps. The secret here is how quickly you can change the power.
Why Speed Matters
Think about your standard resistive heaters. They have way too much thermal mass. Even after you flip the switch off, they stay hot for a long time. That lag is a killer when you’re trying to be precise. Shortwave IR lamps are different. The filament hits its target temperature in milliseconds. When you pair these with a high-frequency SCR or a fast-switching PLC, you can basically throttle the heat in real-time. You can dial the energy back the second the glass hits that critical tempering point. This keeps the surface from overheating while the core finally catches up. It’s a much smoother ride for the material.
The Hardware Side of Things
To get enough heat into the quartz, we usually go with high-wattage halogen tubes. Because they’re short-wave, the energy actually sinks into the glass instead of just warming up the air around it. One tip: make sure your lamp length matches your conveyor footprint. If they don’t line up, you’ll get cold spots, and that’s where the trouble starts. Just a heads-up—running these at max wattage creates some serious heat.**Really serious.**Don’t skimp on your cooling fans or the housing materials. If you do, you’ll find your lamp sockets melting under the radiant load, which is a mess nobody wants to clean up.
Setting It Up
Most of these setups use R7s or Sk15 connectors, so swapping them out on the line is quick and painless. We always suggest quartz-envelope lamps since they can take the heat. If your shop is a bit dusty or prone to contamination, a coated tube is a smart move. It reflects the heat back toward the glass where it belongs. But keep this in mind: those coatings can slightly shift the emission spectrum. After you swap a lamp, you might need to tweak your PID settings to get your tempering curve back to where it needs to be.