How to Heat and Shrink Heatshrink Tubing

In manufacturing, the two most common methods for heating heat shrink tubing are:

• in a chamber designed to heat the heat shrink as part of a production process
• with a hand-held heat gun (or hot air gun) either for one-off/low quantity or manual manufacturing processes

For this exercise, we’ll assume you are using a heat gun.

Before you start:

• Make sure that the heat shrink ends are cut and trimmed smoothly with scissors or a knife. Jagged edges can cause problems such as the heat shrink splitting as you apply it.
• Look at your heat shrink specs. There will be an optimum shrink temperature to bear in mind when setting the temperature of your heat gun.
• Make sure your workplace is well ventilated and think about relevant PPE.
• Make sure that whatever is beyond the heat flow is heat resistant. (Don’t melt that worktop).
• If you will be heat shrinking onto metal or another heat conductive material, you might need to pre-heat it. Otherwise, cold spots can drain heat away and prevent the shrinking process working fully.

Where to apply the heat:

This depends on what’s needed:
1) If the tubing has to be applied at a certain point (at one specific end for example), start the shrinking process in the critical area and work away, towards the other end.
2) If there is no specific need, you can either work your way from the middle outwards or from one end to the other.
3) Heat shrink tube shortens as shrinks, typically by up to 10%. (The heat shrink specs will tell you specifically how much to expect). If you need to avoid this longitudinal shrink then you can shrink one end first, then the other so that the heat shrink is fixed at both ends first (but not in the middle yet). Only then do you work towards the centre.

While you are working:

Apply heat evenly around the tube (don’t linger in any one spot) and eventually it will be fully shrunk onto the component(s) beneath it with no air trapped.

When complete:

Your heat shrink will be shrunk fully and uniformly with no air bubbles or unshrunk areas and there should be no longitudinal movement – it will be fixed, sealing in the item(s) beneath it.
If it’s fully shrunk yet still slides around then unfortunately the specs were wrong for this task and you might want to read Choosing the Right Heat Shrink.