Technical Points of Sealing Technology for Vacuum Packaging Machines
The sealing process of vacuum packaging machines is the core to "locking the low-oxygen environment", and the sealing effect directly determines the shelf life of packaged products (if the seal leaks, the oxygen concentration inside the bag will rise rapidly). The key technical points of its sealing technology revolve around "precise temperature control of heating strips" and "redundant double-seal design", while requiring the coordination of pressure and time, as well as the adaptation of wearing parts. Specific technical details are as follows:
Temperature Control of Heating Strips: Core is "Precise Matching + Uniform Heating"
The goal of temperature control is to bring the heat-sealing layer of the packaging film (e.g., PE, CPP layer) to a "molten state" for bonding, while avoiding damage to the outer layer (e.g., PET, aluminum foil layer) and preventing seal brittleness or leakage.
1. Temperature Matching: Precise Setting Based on Packaging Film Material (Core Parameter)
Different packaging films have significant differences in heat-sealing temperatures. Excessively high temperatures will burn through the film, while excessively low temperatures will fail to achieve molten sealing. The recommended temperature ranges for common materials are as follows:
| Packaging Film Type | Heat-Sealing Temperature Range (℃) | Key Notes |
|---|---|---|
| Ordinary PE Film (Single-layer/Composite Inner Layer) | 120-150 | Low melting point; excessive temperature causes shrinkage/deformation, requiring short sealing time. |
| PE+PET Composite Film | 140-170 | PET layer is high-temperature resistant; higher temperature is needed to ensure PE inner layer melting. |
| Aluminum Foil Composite Film (e.g., PET + Aluminum Foil + PE) | 180-220 | Aluminum foil has heat insulation properties; higher temperature is required to penetrate the outer layer, with extended sealing time. |
| Stretch Film (Vacuum Packaging Machine-Specific) | 160-190 | Uniform thickness; stable temperature is essential to avoid local overheating. |
2. Temperature Uniformity: Key Design to Avoid "Local Leakage"
Heating Strip Material Selection: Industrial-grade equipment mostly adopts "carbon fiber heating strips" or "nichrome heating strips". The former provides more uniform heating (temperature difference ≤ ±5℃), while the latter offers higher temperature resistance and longer service life. Household/commercial machines commonly use ordinary metal heating strips, which require regular inspection for local scorching (scorched areas indicate excessive temperature and need adjustment or replacement).
Temperature Compensation Design: High-end equipment is equipped with "segmented temperature control" function, where the heating strip is divided into 2-3 independently controlled segments. Temperatures can be adjusted for different positions of the bag mouth (e.g., edges, middle) to avoid uneven heating caused by bag mouth wrinkles.
3. Dynamic Adjustment: Real-Time Adaptation to Working Conditions
Temperature is not a fixed value and needs to be adjusted based on the following scenarios:
Material Characteristics: When packaging moist/oily materials (e.g., fresh meat, sauces), the bag mouth is prone to moisture/oil adhesion. Increase the temperature by 5-10℃ to offset insufficient heat sealing caused by moisture heat absorption.
Ambient Temperature: In low-temperature winter environments, film hardness increases; raise the temperature by 10-15℃. In high-temperature summer, lower the temperature by 5-10℃.
Film Thickness: For every 10μm increase in packaging film thickness, raise the temperature by 5-8℃ (e.g., 130℃ for 20μm PE film, 135-140℃ for 30μm PE film).
