Getting Heat-Shrink Right for Aircraft Wiring
When you’re dealing with aviation wire bundles, you’re walking a thin line. You need the heat-shrink tubing to snap into place quickly, but if you push it too far, you’re in trouble. Overheating the insulation can lead to dielectric breakdown or just plain warping. It’s a nightmare. That’s why we use shortwave infrared (IR). It lets us hit that perfect shrink temperature without cooking the wires inside.
Why IR actually works
Think about a standard convection oven. It heats the air, then the air heats the part. It’s slow. Worse, it’s uneven. IR is different. The lamps send out radiation that goes straight through the sleeve and hits the polymer. The sleeve shrinks fast, but the inner wiring stays cool. You get a tight, professional seal without worrying about burning out your insulation.
Controlling the heat
You can’t just blast heat and hope for the best. We use lamps with very specific wattage-per-centimeter ratios to avoid those dreaded hotspots. If you’re working with fluoropolymers like PTFE or ETFE, you need a specific kind of energy to trigger that “shrink memory” in a few seconds. We keep a close eye on the footprint. By simply moving the lamp closer or further from the harness, you can dial in the intensity to fit the size of your bundle.
The tricky parts
Now, here’s the catch: shortwave IR is aggressive. If your conveyor timing is off by even a couple of seconds, you’ll scorch the outer layer. You really need a solid PLC-driven timer and pinpoint positioning to get it right. And a heads-up on the hardware—IR doesn’t heat the air, but the lamp housing itself gets scorching hot. If your shielding isn’t set up correctly, it’ll melt any plastic nearby. To keep things safe, I always suggest adding a non-contact pyrometer. It monitors the surface temperature in real-time. That way, you know the harness has reached the shrink point and gets out of the tunnel before the heat ever reaches the copper.