Ultrasonic Welding
Ultrasonic welding is a processing method that uses microscopic ultrasonic vibrations and pressure to locally generate heat and soften thermoplastic materials, joining them without using sewing thread or adhesive.
Contents5 sections
Definition and Overview
Ultrasonic welding is a method that transmits ultrasonic vibrations from a vibrating tool called a horn and joins materials together with pressure and frictional heat. It is mainly used for thermoplastic resins that soften when heated and harden again, or for fabric, film, and tape containing those components.
In apparel, it is used for areas where you want to reduce seam thickness and thread visibility, as well as for attaching narrow tape and hook and loop fasteners. Unlike metal welding, it is characterized by softening a localized area of the material for a short time and fusing it into one piece.
Position in Product Manufacturing
In the process flow, it is carried out after cutting, as part of the sewing process or as an alternative to it. If necessary, it is combined with sewing, adhesive bonding, seam tape sealing, and similar processes. Because it affects both the surface design and the bond strength, it is important to share the specifications in advance with planning, pattern, and production teams.
Because it does not create holes with a sewing needle, it is suitable for specifications that aim to reduce water penetration from needle holes or to achieve a flat, skin-friendly finish. However, ultrasonic welding alone does not guarantee waterproofing or strength, so design according to the part and usage conditions is necessary.
- In the specification sheet, record the welding position, bonding width, overlap method, front and back sides, and appearance criteria.
- Before mass production, make samples using the actual materials, accessories, and colors, and verify the conditions.
- If there are processes after welding, such as washing, heat treatment, or printing, check their impact.
How to Proceed and Practical Points
First, determine all materials to be joined, such as the main fabric, laminated fabric, film, and tape. Even with the same polyester or nylon, weldability and finish vary depending on surface treatment, coating, thickness, structure, and blend ratio.
Next, select the horn and anvil fixture according to the bonding shape, and adjust conditions such as amplitude, pressure, and processing time. If the conditions are too weak, the joint may peel easily; if too strong, it may cause pinholes, whitening, gloss, hardening, or loss of design detail.
When placing an order, provide the actual materials to be joined, the product specification sheet, sewing specifications, and any unacceptable appearance defects to the processor. It is safer to manage mass-production conditions based on sample conditions and to recheck them when the lot changes for materials or secondary materials.
Quality Control and Differences from Similar Terms
Inspection items include whether there is peeling, the appearance of the joint, variation in bonding width, cracking when bent, and the condition after washing or rubbing. The evaluation methods for tensile and peel strength, the number of tests, and pass/fail criteria should be decided in advance according to the product application and load.
Ultrasonic welding differs in bonding principle from sewing, which joins materials with sewing thread on a sewing machine. It is also different from adhesive bonding, which uses adhesive, and heat pressing, which joins materials with heat and pressure. An ultrasonic welder is not the name of a processing method; it generally refers to the equipment used for ultrasonic welding.
Frequently Asked Questions
What kinds of materials can ultrasonic welding be used for?
In general, it is considered for materials with thermoplastic components, such as films and coatings containing polyester, nylon, and polyurethane. However, material name alone is not enough to determine suitability. Welding tests must be performed on the actual item, including surface treatment, thickness, blend ratio, and any secondary materials to be layered.
Does ultrasonic welding make seams completely waterproof?
Ultrasonic welding is a joining method that does not create needle holes, but it does not by itself guarantee waterproofing for the entire product. Consider the shape of the joint, the waterproofness of the material, edge treatment, and the effects of bending and wear, and verify water resistance if necessary.
What information is needed when ordering ultrasonic welding?
Prepare the actual materials and accessories to be joined, the specification sheet showing the joining locations, overlap direction, bonding width, appearance standards, and the usage environment. Sharing quality standards such as washing and rubbing in advance makes it easier to set processing conditions and align inspection criteria for mass production.
