Fixing the “Cold Spot” Problem in KHS Blow Molding
Ever pull a bottle off the line and see those annoying thin walls or that cloudy, pearlescent look? It’s frustrating. Usually, it comes down to one thing: your heat isn’t hitting the PET preform evenly. For a long time, everyone just stuck with the OEM lamps because they felt “safe.” But honestly? High-spec quartz tubes coming out of domestic shops are now matching—and sometimes beating—those old benchmarks when it comes to a steady thermal field.
Why the heat field actually matters
Here’s the thing. If your lamp has a dip in the middle, your bottle is going to blow out of shape. Period. We spend a lot of time obsessing over the tungsten filament tension and the thickness of the quartz envelope. Why? Because we want the infrared radiation to be rock-solid from one end to the other. No cold spots. We also use a specific doping process in the quartz. It sounds fancy, but it just means we shift the emission spectrum so the PET actually drinks in the energy instead of bouncing it away.
The hardware side of things
Most KHS setups run on high voltage to keep cycle times fast. To handle that, we use R7s and SK15 connectors. They’re great because they don’t loosen up when the pins expand from the heat. Now, a high-output tube can push 2500W. That’s a massive amount of heat density. But there’s a catch. If your reflectors are pitted or oxidized, it doesn’t matter how precise your lamp is. The heat just won’t hit the preform.**Keep your mirrors clean.**If they’re dirty, you’re basically wasting power.
Swapping them out
These are drop-in replacements. You don’t have to mess with your wiring or tear apart your racks. We’ve designed them to mirror the thermal footprint of the originals, but we’ve tweaked the filament so they actually last longer. Just a heads-up: if you’re pushing higher wattage to speed up your throughput, keep an eye on your power supply. If your voltage jumps around, you risk popping the filaments prematurely. A stable power feed is your best friend here.