Hot Cutting Process

• Principle: Utilize heating elements such as a hot cutting knife or electric wire to heat the part of the plastic bag to be cut above the melting point of the plastic, rapidly melting and separating the plastic material to complete the cutting. Meanwhile, during the hot cutting process, heat sealing is usually carried out simultaneously, that is, the edge of the plastic bag is heated and pressurized to seal it, forming a complete closed structure.
• Equipment: Commonly used is the hot cutting bag-making machine, which generally consists of components such as the unwinding roller, guide roller, hot cutting mechanism, and winding roller. The hot cutting mechanism is the core part, including components like the oil cylinder, connecting plate, connecting seat, cutting knife, heat sealing strip, and pressing components. The oil cylinder drives the connecting plate to move up and down, enabling the cutting knife and heat sealing strip to perform hot cutting and heat sealing operations on the plastic film.
• Advantages:
  • Firm Sealing: Heat sealing can achieve a better sealing effect at the opening of the plastic bag, improving its sealing and moisture resistance, effectively preventing the contents inside the bag from leaking or getting damp.
  • Neat Cutting: It can achieve relatively precise and neat cutting, making the edge of the plastic bag smooth and flat, with better appearance quality, enhancing the overall quality of the product.
  • High Production Efficiency: It can quickly complete the hot cutting and heat sealing operations, suitable for large-scale industrial production, which can effectively improve production efficiency and reduce production costs.
• Disadvantages: Due to the need for heating during cutting, the plastic material on both sides of the hot cutting position of the plastic bag is prone to shrink and stretch towards the hot cutting position under the influence of high temperature, resulting in deformation, wrinkling, and other problems, which in turn affect the product quality. However, some advanced hot cutting devices can reduce such defects to a certain extent by adding smoothing parts, pressing components, and other structures.
• Cold Cutting Process
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  • Principle: Use sharp knives or blades to cut the plastic bag at room temperature without the need for additional heating devices. During cutting, the blade cuts through the plastic bag material by mechanical force to achieve the required shape and size.
  • Equipment: The cold cutting bag-making machine has a relatively simple structure, mainly composed of parts such as the material unwinding device, conveying device, cutting device, and material receiving device. The cutting device is usually equipped with high-precision blades or knives, and the driving device such as a motor or cylinder drives the blade to perform the cutting action.
  • Advantages:
    • Low Cost: There is no need for heating equipment, reducing the complexity and manufacturing cost of the equipment. At the same time, it also reduces energy consumption, making the production cost relatively low, suitable for small and medium-sized enterprises and start-up enterprises.
    • Avoid Thermal Deformation: Since the cutting process does not involve heating, problems such as deformation and wrinkling of the plastic bag due to high temperature will not occur, and the original shape and dimensional accuracy of the plastic bag can be better maintained. It is especially suitable for plastic bag products with high dimensional accuracy requirements.
  • Disadvantages:
    • Relatively Weak Sealing Quality: The cold cutting process generally does not have a heat sealing function. If it is necessary to seal the plastic bag, other sealing methods such as glue pasting or ultrasonic sealing usually need to be used, and the firmness and sealing effect of these sealing methods may not be as good as heat sealing.
    • Less Smooth Cutting Surface: Compared with hot cutting, the cutting surface of cold cutting may be slightly rough and not smooth enough, which may not be applicable in some application scenarios with high requirements for appearance quality, but it has little impact on some ordinary plastic bags.

Cold Cutting Process

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  • Principle: Use sharp knives or blades to cut the plastic bag at room temperature without the need for additional heating devices. During cutting, the blade cuts through the plastic bag material by mechanical force to achieve the required shape and size.
  • Equipment: The cold cutting bag-making machine has a relatively simple structure, mainly composed of parts such as the material unwinding device, conveying device, cutting device, and material receiving device. The cutting device is usually equipped with high-precision blades or knives, and the driving device such as a motor or cylinder drives the blade to perform the cutting action.
  • Advantages:
    • Low Cost: There is no need for heating equipment, reducing the complexity and manufacturing cost of the equipment. At the same time, it also reduces energy consumption, making the production cost relatively low, suitable for small and medium-sized enterprises and start-up enterprises.
    • Avoid Thermal Deformation: Since the cutting process does not involve heating, problems such as deformation and wrinkling of the plastic bag due to high temperature will not occur, and the original shape and dimensional accuracy of the plastic bag can be better maintained. It is especially suitable for plastic bag products with high dimensional accuracy requirements.
  • Disadvantages:
    • Relatively Weak Sealing Quality: The cold cutting process generally does not have a heat sealing function. If it is necessary to seal the plastic bag, other sealing methods such as glue pasting or ultrasonic sealing usually need to be used, and the firmness and sealing effect of these sealing methods may not be as good as heat sealing.
    • Less Smooth Cutting Surface: Compared with hot cutting, the cutting surface of cold cutting may be slightly rough and not smooth enough, which may not be applicable in some application scenarios with high requirements for appearance quality, but it has little impact on some ordinary plastic bags.

Ultrasonic Cutting Process

• Equipment: It mainly includes components such as an ultrasonic generator, transducer, amplitude transformer, and cutting tool. The ultrasonic generator generates high-frequency electrical signals, the transducer converts the electrical signals into mechanical vibrations, the amplitude transformer amplifies and focuses the vibrations, and finally, the cutting tool transfers the vibrations to the plastic bag for cutting.
• Advantages:
  • Good Cut Quality: The cutting surface is smooth, flat, without burrs or flash, and the cut quality is better than that of the cold cutting process, approaching the effect of hot cutting.
  • High Cutting Precision: It can achieve high-precision cutting, and has a good cutting effect for complex shapes and sizes of plastic bags, which can meet some special packaging requirements.
  • High Safety: There is no need to use sharp blades, avoiding the risk of cuts to operators when in contact with the blades, improving the safety of the production process.
• Disadvantages:
  • High Equipment Cost: The price of ultrasonic cutting equipment is relatively high, with a large initial investment, increasing the production cost of the enterprise.
  • Limited Efficiency: The speed of ultrasonic cutting is relatively slow, especially for thicker plastic bags, the cutting efficiency will be further reduced, affecting production efficiency.

Laser Cutting Process

• Principle: The ultrasonic generator generates high-frequency vibrations, causing the cutting tool to also vibrate at high frequency. When the tool contacts the plastic bag, the energy of the high-frequency vibration is transferred to the plastic bag, generating frictional heat between the plastic molecules, thereby melting and cutting the plastic bag locally.
• Equipment: It mainly includes components such as an ultrasonic generator, transducer, amplitude transformer, and cutting tool. The ultrasonic generator generates high-frequency electrical signals, the transducer converts the electrical signals into mechanical vibrations, the amplitude transformer amplifies and focuses the vibrations, and finally, the cutting tool transfers the vibrations to the plastic bag for cutting.
• Advantages:
  • Good Cut Quality: The cutting surface is smooth, flat, without burrs or flash, and the cut quality is better than that of the cold cutting process, approaching the effect of hot cutting.
  • High Cutting Precision: It can achieve high-precision cutting, and has a good cutting effect for complex shapes and sizes of plastic bags, which can meet some special packaging requirements.
  • High Safety: There is no need to use sharp blades, avoiding the risk of cuts to operators when in contact with the blades, improving the safety of the production process.
• Disadvantages:
  • High Equipment Cost: The price of ultrasonic cutting equipment is relatively high, with a large initial investment, increasing the production cost of the enterprise.
  • Limited Efficiency: The speed of ultrasonic cutting is relatively slow, especially for thicker plastic bags, the cutting efficiency will be further reduced, affecting production efficiency.
• Principle: Utilize a high-energy-density laser beam to irradiate the plastic bag, instantly melting or vaporizing the plastic bag material to achieve cutting. The energy of the laser beam is highly concentrated, enabling precise control of the cutting path and depth to achieve the desired cutting effect.
• Equipment: It mainly consists of components such as a laser generator, laser transmission system, focusing system, and numerical control system. The laser generator produces a high-energy laser beam, which is transmitted to the focusing system through the laser transmission system. The focusing system focuses the laser beam onto a small area on the surface of the plastic bag, and the numerical control system controls the movement of the laser beam and the cutting parameters to achieve precise cutting.
• Advantages:
  • High-Precision Cutting: It can achieve extremely high cutting precision, capable of cutting out very fine patterns and shapes, meeting personalized and customized packaging requirements, such as making plastic bags with special shapes or hollow patterns.
  • Excellent Cut Quality: The cutting surface is smooth, neat, without thermal deformation, burrs, or burn marks, etc., with excellent cut quality, which can improve the appearance quality and performance of the plastic bag.
  • Non-Contact Cutting: During the laser cutting process, there is no direct contact with the plastic bag, avoiding mechanical extrusion and friction on the plastic bag material, reducing material damage and deformation. At the same time, it also reduces blade wear and replacement costs.
• Disadvantages:
  • High Equipment Cost: Laser cutting equipment is expensive, and its operation and maintenance costs are also high. It requires professional technicians for operation and maintenance, increasing the production cost and technical threshold of the enterprise.
  • Relatively Low Efficiency: The speed of laser cutting is relatively slow, especially for large-area or batch cutting of plastic bags, the production efficiency is low, and it is not suitable for large-scale industrial production.
  • Material Requirements: Not all types of plastic materials are suitable for laser cutting. Some plastics may have adverse reactions under laser irradiation, affecting the cutting effect and material performance.