Causes uneven pressure in the heat sealing film

[China Packaging Network News] Several factors can lead to uneven pressure during the heat sealing process of film wrapping. Understanding these causes is essential for maintaining consistent and effective sealing performance. Here are the main reasons:

1. Deformation of the Heat Sealing Knife

Heat sealing knives are typically made from aluminum or copper, materials known for their excellent thermal conductivity. However, both materials are relatively soft, which makes them prone to deformation if not installed correctly. Improper tightening methods during installation can result in uneven stress distribution across the knife. Additionally, frequent tool changes may cause the knife to warp over time. To avoid this, it's crucial to use the correct installation techniques and ensure even pressure application.

2. Poor Machining Accuracy of the Heat Sealing Knife

If the machining precision of the heat-sealing knife is low, its surface may become uneven. This irregularity can lead to inconsistent pressure during the sealing process, resulting in weaker seals and potentially compromising the integrity of the packaging bag. Ensuring high-quality manufacturing of the knife is key to achieving uniform pressure and reliable sealing results.

3. Contamination or Damage on the Heat Sealing Knife Surface

The presence of dirt, scratches, or other imperfections on the surface of the heat-sealing knife can also cause uneven pressure. Moreover, if molten resin adheres to the knife and isn't cleaned promptly, it can affect the sealing strength. It’s important to thoroughly clean the heat-sealing knife during each tool change to prevent residue buildup and maintain optimal performance.

4. Hardness and Elasticity of the Silicone Skin

The quality of the silicone skin plays a critical role in ensuring even heat sealing pressure. A good silicone skin should have appropriate hardness and elasticity. Over time, due to wear or aging, the silicone skin may lose its flexibility, leading to inconsistent pressure and potential bubbles forming during the sealing process. These issues can significantly reduce the effectiveness of the seal. When selecting a silicone skin, it's important to consider its hardness. For example, when sealing aluminum foil bags, a hardness of HS70 is recommended, while general materials usually require a hardness between HS50 and HS60.