Key Points for Heat Sealing in Zipper Bag Production
To ensure zipper bags have the necessary convenience and excellent seal integrity, it is crucial that the zipper head area remains airtight. Seal integrity is often the most challenging and critical aspect of production. Regardless of the material combination used, a well-matched heat tolerance across all materials, including the zipper, is essential to achieve the best results. Compliance with national standards for zipper functionality and specific customer requirements must also be met.
Common issues that can arise during this process include:
1）Insecure Heat Seal at the Zipper Head (Insufficient Temperature): This can lead to air or liquid leakage. When the temperature is too low, the heat seal may be weak, particularly around the zipper head, compromising the bag’s overall sealing.
2）Overheating and Crushing of the Zipper Head: Excessive temperature may damage the surface and inner layers, resulting in leaks. High temperatures can crush the material at the zipper head, making it prone to air and liquid leakage.
3）Incorrect Heat-Sealing Orientation for Single-Track Zippers: Single-track zippers have distinct directions—one for opening and one for the bag interior. The difference in clamping force between these directions is significant. If sealed in the wrong direction, the product may be considered defective due to excessive inner sealing force, making it hard to open, or prone to bursting when filled. For this reason, most single-track zippers have a marking to indicate the opening direction, and it’s essential for operators to align this correctly.
4）Low Inner Clamping Force of the Zipper: This issue may stem from two primary causes: poor initial zipper quality or incorrect setup during production, such as misaligned zipper plates or skewed cooling blades. Additionally, if the heat-sealing blade presses on the zipper grooves, the zipper may become stuck and unable to open. Low inner clamping force can lead to internal ruptures during bag use.
5）Low Outer Clamping Force of the Zipper: Similar to low inner clamping force, this issue affects how securely the bag seals. Bag size also impacts the zipper's outer clamping force; smaller bags may require less force, while larger bags need a stronger clamping force for effective sealing.
6）Leakage in Double-Track Zipper Bags for Liquids: Liquid-tight double-track zipper bags often experience leakage near the zipper head. Proper fusion of the two zipper tracks is crucial but challenging. Operators may try to increase pressure to improve fusion at the zipper head, sometimes causing damage to the bag body material and leading to leakage. For vacuum-sealed double-track zipper bags, the zipper’s clamping force must be sufficient to maintain a vacuum state without loosening.
Effective management of these factors is essential to maintaining seal integrity and ensuring product quality in zipper bag production.
In summary, producing high-quality composite flexible zipper bags is a complex task, requiring meticulous attention to every detail. Small mistakes can easily compromise the final product. Each type of flexible zipper bag, with its unique material combinations and zipper specifications, presents distinct challenges and control points. Achieving consistency and reliability in production demands not only stable processing techniques and materials but also careful consideration of all related procedures and even pre-production design details. Anticipating potential issues ahead of production is crucial to avoid costly mistakes that could impact economic efficiency and limit competitive advantage.
