In the modern production of functional clothing, new methods of thread-free connection of parts, one of which is welding, are of great importance. The world's leading manufacturers actively use welded joints in the production of products made of various materials.

Replacement of thread seams with welded ones has a number of advantages:

• no punctures – the waterproofness of the material is not violated, the insulation does not come out through the seam;
• higher performance due to the combination of several operations;
• thermal and/or adhesive edge treatment, which is important for bulk and knitted fabrics;
• cost reduction – no threads, needles, spools, etc.;
• modern, attractive, competitive appearance of the product.

Thread technologies are slowly fading into the background: abroad they already make up 60% of the total production, but in Russia they are still sewing 98% with threads. Although recently, the interest of Russian manufacturers in new technologies in the trend of import substitution has been significantly noticeable.

Of course, everything is not so simple, and threadless technologies require more advanced equipment, components, knowledge of technologies, but at the same time they are already available even to small productions.

At the moment , the following threadless technologies are widely used:

• hot-glue welding (TCS);
• ultrasonic welding (UZS);
• welding with high frequency current (HDV);
• hot air welding;
• hot wedge welding.

The last three technologies are mainly used for welding PVC fabrics in the production of waterproof work clothes, inflatable boats, summer gazebos, inflatable structures. We will not dwell on them in this review, but will take a closer look at the first two as the most interesting.

Hot-glue welding

Its essence is in gluing two materials together with the help of hot-glue and hot-glue film films. The technology is simple, any sewing production can master it, from a sewing workshop to large-scale production.

Products made of thin elastic knitwear of sportswear, underwear and thermal underwear are made on modern equipment – hot-glue machines, outwardly resembling an overlock with a software control unit. The machines produce welding at low temperatures, at which the knitwear does not deform. The seam turns out to be flat without loss of elasticity in all directions, which is impossible to achieve with a thread seam. Some machines are used for lap welding of the material, others for bending and edging the edges. A special elastic thermal adhesive tape is used as an expendable material.

But the most popular thread-free technology at the moment is hot-glue welding of cut elements and decorative finishing on thermal presses. They are available at almost every enterprise, they are very versatile and significantly expand production capabilities. At the same time, their cost is not very high. Thermal presses are simple and unpretentious in operation, it is not difficult to learn how to work on them. The only thing worth considering is that the press should be either with a moving table, or with an increased lifting height of the working heating plate, sufficient for comfortable and safe operation. In addition, "book" manual thermal presses are not suitable for this technology, since when using them, significant displacements of the workpieces between themselves are possible during the lowering of the working plate. Welding and decorative finishing of slotted (sew-in) and patch pockets, welding of zippers, application of shoulder, elbow and other reinforcements, welding (bonding) of various fabrics and materials, welding of labels, logos and reflective elements, increasing the rigidity of windproof slats of zippers and hood visors are performed on thermal presses using thermoclue Film films.

Let's consider as an illustrative example the technology of hot-glue welding of an overhead chest or shoulder pocket.

1. First, the necessary parts are cut, which is produced on a laser-cut machine. Only on this machine it is possible to achieve the perfect accuracy of the parts and melt the edges of the cut.
2. A transparent double-sided hot-glue film Single Side Film cut along the perimeter of the product and along the zipper opening is welded to the pocket part with an iron or on a thermal press. After that, the protective paper layer is removed from it.
3. A waterproof waterproof zipper is also welded to the pocket cut with an iron or press to eliminate the displacement of parts during the final assembly of the workpiece and during welding.
4. On a thermal press, a multilayer sandwich is assembled from fabric, zipper and hot-glue films, on which a mandrel is placed on top in the shape of a pocket so that the heating is local, does not deform the material and does not affect the zipper dog with a tongue.
5. After assembly, the pocket is welded.

Assembly diagram of patch pocket parts for hot-glue welding

1– decorative thermal adhesive film Decoration Film;

2– outer pocket fabric;

3– Adhesive film Single Side Film;

4–moisture-proof zipper waterproof;

5– inner fabric (lining or outer fabric on which the pocket is welded).

Ultrasonic welding

Initially, this technology had a narrow scope of application: it was used to work with non-woven materials in the production of filters, disposable clothing, packaging and home textiles. It was practically not used in the manufacture of products made of woven materials due to the insufficient strength of the seam and the piercing sound that the machine makes when working. But technology does not stand still – these shortcomings have been eliminated. There are noiseless machines that work with a variety of different materials - almost all synthetic, blended, knitted fabrics.

Ultrasonic welding does not require consumables (threads, needles, spools, sealing tapes). On ultrasonic machines, it is possible to simultaneously cut the edge, cut, decorative cutting of the pattern, heat treatment of the cut edge, crowding, including the logo (even on the skin), simultaneously with the connection of parts. In addition, butt seams can be made on such equipment, resulting in a flat seam. This allows you to work with a cut that is quite complex in geometry. But this seam is not strong enough due to the small area of the joint, and it must be additionally glued with a special textile-based tape. Ultrasonic machines are mostly made in the housing of standard industrial-class sewing machines, which greatly simplifies and reduces the time for retraining seamstresses and the transition to new thread-free technologies.

All these advantages of modern equipment significantly expand the capabilities of the enterprise, increase productivity, reduce the cost of the product, increase profitability and competitiveness, which is strategically important in our difficult times.

Author: Sergey Fedorov