How much will heat shrink actually shrink?

How Much Will Heat Shrink Tubing Actually Shrink? A Detailed Guide

Heat shrink tubing is a versatile and indispensable tool for insulating wires, providing strain relief, and protecting connections. One of the most common questions people have when using heat shrink tubing is, "How much will it actually shrink?" Understanding the shrink ratio and the factors that affect it is crucial to selecting the right tubing for your project. In this blog, we'll explore how heat shrink tubing works, how much it shrinks, and how to choose the best option for your needs.

Understanding Shrink Ratios

The shrink ratio is the most important factor in determining how much heat shrink tubing will shrink. The shrink ratio is expressed as a ratio of the tubing's original (expanded) diameter to its final (recovered) diameter after heat is applied.

For example:

• 2:1 Shrink Ratio: This is the most common shrink ratio, meaning the tubing will shrink to half of its original diameter. If the tubing starts at 10mm in diameter, it will shrink down to 5mm when heat is applied.
• 3:1 Shrink Ratio: In this case, the tubing will shrink to one-third of its original diameter. A 9mm tube would shrink down to 3mm.
• 4:1 Shrink Ratio: This ratio means the tubing will shrink to a quarter of its original diameter. A 12mm tube would shrink down to 3mm.

Higher shrink ratios are useful when you need the tubing to fit over larger components before shrinking tightly around a smaller object.

How to Calculate the Final Diameter

To determine how much a particular piece of heat shrink tubing will shrink, you can use the following formula:

Final Diameter = Original Diameter / Shrink Ratio

For example:

•  If you have tubing with an original diameter of 12mm and a 3:1 shrink ratio, the final diameter will be:

Final Diameter = 12mm / 3 = 4mm

This means that the tubing will shrink to a diameter of 4mm when heat is applied.

Factors That Affect Shrinkage

While the shrink ratio gives a good estimate of how much the tubing will shrink, several factors can influence the actual shrinkage:

1. Material Type:   Different materials have different shrink characteristics. Common materials include polyolefin, PVC, and fluoropolymer. Polyolefin is the most widely used and offers consistent shrinkage, while other materials might have slightly different properties.

2. Temperature:  The temperature required to shrink the tubing varies depending on the material. Most heat shrink tubing begins to shrink around 90°C (194°F), but higher temperatures might be needed for complete shrinkage. The correct application of heat is crucial to achieving the full shrink ratio.

3. Application Method:  The method used to apply heat—whether a heat gun, lighter, or oven—can affect the tubing’s shrinkage. Uneven heating or excessive heat can lead to uneven shrinkage or even damage the tubing.

4. Wall Thickness:  Thicker-walled tubing may not shrink as easily as thinner-walled tubing, and it may require more heat or time to achieve full shrinkage.

5. Tubing Length:  While the diameter of the tubing shrinks according to the shrink ratio, the length of the tubing may also change slightly. Generally, heat shrink tubing will shorten slightly when heated, but this effect is minimal compared to the diameter reduction.

Choosing the Right Size Tubing

To choose the correct size of heat shrink tubing for your project, consider both the original and final diameters:

• Measure the Diameter: Start by measuring the largest diameter of the component you want to cover (e.g., the diameter of a connector or wire bundle). Ensure that the tubing's original diameter is large enough to fit over this component.
• Consider the Final Diameter: Ensure that the tubing's final diameter, after shrinking, will be small enough to fit snugly around the smallest part of your wire or component.

For example, if you need to cover a 10mm connector but want the tubing to shrink down tightly around a 4mm wire, you might choose a 12mm tubing with a 3:1 shrink ratio. This tubing would shrink down to 4mm, fitting snugly around the wire.

Common Shrink Ratios and Their Applications

• 2:1 Shrink Ratio: Ideal for general-purpose use, covering wires, splices, and small connectors. It’s perfect for applications where the tubing doesn’t need to cover components of vastly different sizes.
• 3:1 Shrink Ratio: Best for applications where the tubing needs to fit over a larger connector or component before shrinking down to cover a much smaller wire or terminal.
• 4:1 Shrink Ratio: Useful for complex shapes, large connectors, or situations where maximum shrinkage is needed to achieve a tight fit.

Conclusion

Understanding how much heat shrink tubing will actually shrink is key to selecting the right product for your needs. By considering the shrink ratio, material type, and the specific requirements of your project, you can ensure a secure, professional finish every time.

Whether you’re insulating wires, providing strain relief, or waterproofing connections, knowing how to calculate and apply heat shrink tubing will make your work more effective and efficient. Always double-check the specifications of the tubing you choose to ensure it meets the demands of your specific application. With the right knowledge and tools, you can achieve the perfect shrink every time.