Heat sealing and ultrasonic sealing are two popular packaging solutions that are often compared. You may know that heat sealing has the characteristics of strong sealing and firm packaging. While ultrasonic sealing has higher precision. But you may not know the more detailed and comprehensive comparison. Next, I will give you a detailed introduction to their characteristics.
What is Ultrasonic Sealing
Ultrasonic sealing uses ultrasonic energy to bond materials by affecting their molecular structure with high-frequency vibrations. The process makes the material soft. The materials are held together by a sealing anvil, bonding to form a seal.
In more detail, the welding tool concentrates ultrasonic energy on the material. Causing the two sealing surfaces to vibrate and generate heat. Melts the surfaces and creates a seal. Ultrasonic sealing is particularly suitable for applications requiring strong, precise, and clean seals. Especially in industries where hygiene and material integrity are critical.
What is Heat Sealing
Heat sealing involves using heat and pressure to seal materials. Careful control of dwell time and cooling time is especially critical. If these factors are not precisely managed, the seal may become weak or even damage the packaging. As its name suggests, the process generates a significant amount of heat to create a strong seal. However, this heat can also affect the quality of the product or introduce safety risks. It is widely used in many industries, like food, pharmaceuticals, and electronics.
Comparison of Ultrasonic Sealing and Heat Sealing
Cost
The energy output of ultrasonic sealing is less than the energy output of heat sealing. For example, conduction heat-sealing systems may need four 500-watt cartridge heaters to continuously maintain seal-bar temperatures. While a similar capacity ultrasonic welder needs a power supply rated at 1500 watts peak power. And it consumes power only in short bursts.
In material per bag with the same net product volume, ultrasonic sealing uses less materials in sealing than heat sealing. The seal of heat sealing is wider. So the material cost of ultrasonic sealing is less than the material cost of heat sealing too.
Seal Strength
In general, heat sealing has higher seal strength. But to the materials that are more compatible with ultrasonic technology, the seal strength of ultrasonic sealing is higher.
Safety during Operation
Heat sealing generates a significant amount of heat. While ultrasonic sealing produces heat only within the material being welded. And the heat sealing machine is more complex. So heat sealing carries a higher risk of safety hazards.
Maintenance and Repair
Heat sealing machines are more complex in structure and have higher mechanical requirements. So they require more frequent maintenance and you have to check them more often. And they release a lot of heat during operation. That makes them more prone to damage.
Ultrasonic sealing machines are more stable and easier to test and repair when they have a problem. This saves you a lot of trouble. Additionally, they are less likely to be damaged compared to heat sealers.
Sealing Speed
Ultrasonic sealing is generally faster because the sealing process is nearly instantaneous. It can seal materials in milliseconds. Ultrasonic vibrations generate localized heat at the sealing interface. It lets the materials bond quickly. And there is no need for a cooling phase in the process compared to heat sealing.
Seal Effectiveness
Unlike heat sealing, ultrasonic sealing does not use a lot of heat. That reduces the risk of uneven sealing and packaging damage. Ultrasonic sealing has a higher degree of precision. It minimizes the risk of product leakage and ensures the reliability of the seal.
Some products may leave residues or plant matter, powders, beverages and oils on the sealing surface. In heat sealing, they may be sealed into the packaging bag. The contamination occurs. Or it may affect the sealing effect. Bring about the uneven sealing or even the sealing failure. The vibration motion of ultrasonic welding can shake contaminants out of the sealing area. The vibration and pressure can also cut larger residues into smaller pieces and shake them out of the sealing area. This further ensures the effectiveness of ultrasonic sealing. So that it can be reliably sealed even if there are residues in the sealing area.
Precision
Compared to heat sealing, ultrasonic sealing has higher accuracy. It offers more precise and more programmable control over more than a dozen factors in sealing. While heat sealing only offers the control of factors like temperature, pressure, dwell time, and cooling time. More precise control of ultrasonic sealing guarantees reliability and flexibility.
Package Safety
Heat sealing has a wider seal. And a wider seal often means a safer and more secure package. The increased sealing area allows the seal to withstand greater tensile and compressive forces. A wider seal distributes externally applied stress more evenly. Reducing the concentration of stress at a single point. Therefore, lowering the risk of seal failure. In contrast, ultrasonic sealing has a smaller seal. This feature could potentially lead to quality control issues.
Regulatory Advantage
Among the sealing films sold on the market, more sealing films are designed for heat sealing. The heat sealing technology is widely used and well-established. It has more regulatory advantages.
Working Principles
Ultrasonic Sealing Woking Principles
The main difference between ultrasonic sealing and heat sealing is that the heat generated by ultrasonic sealing is generated only within the material being welded. Specifically, ultrasonic sealing uses sound waves to vibrate at the molecular level of the material to generate heat. This vibration has a precise frequency. The sealing speed is fast. It can be sealed with a time of between 100 and 200 milliseconds. The parts are bonded together by cohesive or form-fit joints. In this way, it can form a strong molecular bond.
The sealing machine has a number of components. Including a power supply, a stack consisting of a converter, booter and horn, a pneumatic actuator and a base with metal fixture or anvil. The converter converts the high-frequency electrical signal into mechanical vibrations. And the booster amplifies these vibrations to increase the amplitude to the required level.
The horn sends mechanical vibrations to the interface between the surfaces of the materials. Intermolecular and surface friction occurs. This friction generates heat. Melt between the two parts. And solidifies into a welded bond.
Heat Sealing Working Principles
To ensure proper sealing, a heat sealer requires precise control over temperature, pressure, dwell time, and cooling time. The adjustment of parameters are based on the materials used. You should take good control of these factors. The process includes applying heat to melt the plastic layers and pressure to allow the heat to penetrate through all layers. Make the material melt and bond together. The cooling phase then solidifies the bond. At this time, the pressure must be maintained until the cooling is complete. It is crucial to strictly manage these factors. Because any mistake in those factors could result in weak or failed seals in the packaging.
Application of Ultrasonic Sealing
Ultrasonic sealing is known for its high precision. Particularly suitable for products that require a high level of accuracy. Additionally, the heat needed for ultrasonic sealing is generated only within the material being welded. This feature reduces the risk of uneven or damaged seals.
| Industries | Examples of Products | Packaging Features |
| Food | salad from the chiller, perishable foods, ready-meals in bags, drinks cartons, seals on milk | tight sealing, functional |
| Electronics | cables, wire harnesses, smartphone batteries, sensors | precise, the heat needed for ultrasonic sealing is generated only within the material being welded |
| Medical and Pharmaceutical | sterile surgical gowns, masks, liquid medicine pouches, pharmaceutical trays | precise, the heat needed for ultrasonic sealing is generated only within the material being welded, sterile seals |
Application of Heat Sealing
Heat sealing is widely used, it has strong sealing. Popular in many industries.
| Industries | Examples of Products | Packaging Features |
| Food | food in plastic bags or foil bags, vacuum packaging: products like meats, dried goods, and coffee beans | strong sealing, preventing oxygen and moisture from entering, sturdy packaging |
| Household Products | laundry detergents and cleaning agents | strong sealing, sturdy packaging, leak-proof seals |
| Medical Packaging | syringes, bandages, tablets, liquid medicine pouches | strong sealing, ensuring the safety of products |
Conclusion
The key to choosing between ultrasonic sealing and heat sealing lies in your specific needs. If you require a sealing method with high precision and safer operation, then ultrasonic sealing is the better choice. If you need a more robust and secure package, heat sealing would be the way to go. For more detailed considerations, you can refer to the points I outlined earlier.
