Ultrasonic Welding and Cutting Technology: Principles, Power & Frequency, Advantages & Disadvantages

1. Principle of Ultrasonic Technology
Ultrasonic technology works by rapidly heating molecules, generating high heat to instantly weld, bond, or cut materials. The edges are smooth and neat, without any burrs or yellowing effects.

2. Power and Frequency

Power (W): Refers to the power emitted by the ultrasonic machine's chassis.
Frequency (K or Hz): Refers to the frequency of the sound waves emitted by the ultrasonic transducer.
Power and frequency are interrelated, working in a cycle. Once the Automatic Ultrasonic Machine is powered on, the energy is converted from the chassis to the transducer, and the two parts work together as one.
Common configurations include:

15kHz: 2500W / 1500W / 3000W / 4200W (commonly used for automatic frequency tracking and variable frequency digital systems in material feeding welding machines).
20kHz: 2000W
18kHz: 2500W
28kHz: 800W
35kHz: 500W
In general, the higher the frequency, the lower the power. The power can be adjusted slightly at the same frequency, but the frequency itself is not adjustable.

How to Choose Frequency and Power for Clients' Products
To select the right frequency and power, we consult with the client to understand their products. Thicker materials and larger areas require lower frequency and higher power for greater ultrasonic impact, which results in stronger welding or cutting effects.

3. Advantages and Disadvantages of Ultrasonic Technology
Ultrasonic technology is mainly used for fine fibers, synthetic materials, non-woven fabrics, nylon, PP, PE, and similar materials. Pure cotton or materials with a high cotton content cannot be bonded, though they can be cut (but the edges won't melt and will create fraying). For materials that can be cut, ultrasonic cutting leaves smooth, soft edges without fraying, burn marks, or balling.
For welding, bonding, and composite processes using ultrasonic technology, the design must include patterns, usually dashed lines or dots. Solid lines or smooth surfaces cannot be used because the fabric remains flat during the process and doesn't move forward. This may lead to material blockage at the inlet and fusion of the fabric at the welded areas, making it too stiff.

Ultrasonic welding/cutting can only process a single product or a single-layer cut at a time. It is not suitable for multiple layers or multiple products being processed simultaneously as the ultrasonic energy will bond them together, making separation difficult. Typically, ultrasonic molds are designed for individual products, so only one product can be welded at a time.
Mold Considerations:
Ultrasonic cutting works best when the cutting direction is longitudinal. Horizontal cutting is challenging as it is difficult to cut through. Most patterns are irregular and not perfectly straight.

Unlike electric heating equipment, where temperature can be adjusted, ultrasonic equipment generates heat instantaneously, and the temperature cannot be controlled. However, power can be adjusted within the same frequency range.

4. Non-Standard Equipment for Width Considerations
When communicating with clients, it's crucial to consider their needs in as much detail as possible to offer broader product solutions. The width of raw material is a critical factor, and by understanding the full range of products and dimensions the client works with, we can provide accurate pricing.

Slitting and Cross-Cutting Machines:
For material widths divided by product width + 1, this calculates the required number of ultrasonic units. Depending on the product dimensions, we determine how many ultrasonic heads are needed. For material widths exceeding 80cm, we recommend a single knife; smaller specifications depend on the material and product size.

Composite Machines:
The material width divided by 153/200 (rounded) gives the number of ultrasonic units required. In composite processing, the width of the welding head should cover the entire fabric width without gaps.

Mop Strip Machines:
Simply divide fabric width by 153mm and use the integer result, as mop strips require a set width and allow for gaps in the welding head.

5. Edge Alignment System Considerations
The edge alignment system is designed to correct any deviation in the fabric’s movement. The system uses the fabric's edge as a guide, and the alignment motor moves slightly left and right to prevent any fabric misalignment. This minor movement does not affect the cutting dimensions.
However, for fabrics with stripes or patterns that require precise alignment to the design, the alignment system might struggle to maintain accuracy, as fabric misalignment will shift the cutting line.

6. Mold Considerations
Standardized molds follow a 1:1 design size.
Round Molds: For machines that work in an up-and-down motion, the mold size can be customized without adjusting for shrinkage, as the fabric remains fixed. However, in machines that roll, shrinkage adjustments are necessary, especially for fabrics with high elasticity.
Thicker Fabrics and Welding: For thicker fabrics requiring welding, actual samples are needed to determine the right cutting and embossing spacing.