Ultrasonic seamless stitching is an advanced technology for joining synthetic materials and blends to produce continuous and impermeable seams. Fabrics can be 100% thermoplastic synthetic fibers or blended fibers with up to 40% natural fiber content. Ultrasonic seamless stitching technology is generally achieved by ultrasonic sewing machines. Ultrasonic sewing machines use disc-type welding heads for roll welding, cleverly converting the longitudinal vibration of the transducer and the radial vibration of the disc-type welding head, radiating 360° outward along the diameter direction, thereby achieving seamless stitching of materials.
During the ultrasonic seamless stitching process, the material is fed between the vibrating ultrasonic horn and the fixed anvil (or moving wheel). High-frequency mechanical vibrations (20-40 kHz) through thermoplastic parts will generate friction heat at the interface, thereby obtaining sufficient temperature to melt and bond the material. Because the heat required for bonding is generated at the interface (rather than from the outside of the material), the ultrasonic welding process starts exactly at the interface. For non-synthetic fabrics or blends with more than 40% natural fiber content, the heat-activated material is placed between the two pieces of fabric. The vibration and pressure of ultrasound cause the heat-activated material to melt and penetrate the inter-fiber spaces of the fabric.
Application Range
Ultrasonic seamless sewing plays an increasingly important role in various industries, and also plays an important role in clothing manufacturing and development.
- Apparel Industry
For clothing manufacturers, ultrasonic sewing machines are very fast, clean, and economical. Ultrasonic waves can be used on a variety of man-made fabrics and plastics, and natural fabrics can also be used with a minimum content of at least 60% thermoplastics. Ultrasonic seamless sewing technology provides beautiful and smooth seams for lightweight underwear and sportswear fabrics, and is also very suitable for connection with Velcro and polyester tapes. Fabric seams can be completely flat against the body with adhesive tape, which is 4 times stronger than sewn seams.
- Medical Industry
Ultrasonic sewing machines are able to produce commonly used clothing, including protective clothing, disposable hospital surgical gowns, shoe covers, masks, baby warm clothes, filters, bags, curtains, sails, and mesh stitching etc. Ultrasonic seams are beneficial in the manufacture of these items because the sealed edges and seams without stitching holes are impermeable to chemicals, liquids, blood-borne pathogens or other particles.
- Outdoor Products Industry
Since ultrasonic seams are airtight, resulting in strong seams and reduced hole formation, the technology is also used in the manufacture of outdoor products such as sails and parachutes. The technology is widely used in clothing for sports such as skiing, cycling, sailing, mountaineering, paddling, hiking, waterproof backpacks, outdoor tents, military equipment, etc.
Advantages of Ultrasonic Seamless Seaming Technology
1. Lighter Quality
Seamless seams are lighter than traditional stitching. After drying, they can reduce the total weight of the seam by up to 30%.
Strong and Stretchable
Seamless bonding is 40% less restrictive than sewn seams and has excellent stretch and recovery. This means more freedom of movement, more comfort, and less interference. The strength of seamless bonding is as strong as stitching, and the fabric is also softer.
2. Waterproof and Airtight
Ultrasonic seams enhance the water resistance of clothing. Because it is bonded, there are no pinholes for water to penetrate. At the same time, the stitching technology also improves the windproofness of the material due to the nature of having no pinholes.
3. Cost Savings
Ultrasonic seamless stitching technology can be used on fabrics containing a large amount of thermoplastic fibers. The technology is less wasteful because it does not require needles, threads, solvents, adhesives, or mechanical fasteners. There is no limit to the stitching speed, and there is no need to worry about the need to re-shuttle the bobbin or replace the bobbin.
Scope of Application
For fabrics and textiles used for ultrasonic welding, some requirements must be met:
1. The material being stitched needs a wide melting range and a high coefficient of friction, and the fabric must always have a consistent thickness.
2. In order to reach the melting point that allows ultrasonic bonding, the textile must have a minimum thermoplastic content of 20%, and there must be enough strength within the material to withstand the welding process.
Ultrasonic sewing is generally suitable for synthetic fabrics because they are thermoplastic and can be softened and bonded when subjected to ultrasonic energy. Polyester and nylon are common and popular choices for fabric materials used for ultrasonic welding and sewing. Nylon is a good fiber choice because of its excellent properties. It is a strong, primary fiber; it is elastic when stretched and has excellent abrasion resistance. Polyester (PET) is the most commonly used synthetic fiber overall. Polyester has similar properties to nylon. It has strength and abrasion resistance and has a permanent heat set.
