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Welding as a process in garment manufacture involves the sealing together of thermoplastic materials but the heat is not applied externally as is normally the case with the fusing of interlinings. The heat must be generated within the thermoplastic materials.
If two hard materials are vibrated against each other, they become hot at the point of contact. If plies of thermoplastic materials are placed between the points of vibration, heat will be generated internally in the materials where they touch and if this heat is sufficient, they will melt and can be pressed together so that a bond is formed.
A device which changes an input of electric current into mechanical vibrations is known as a transducer and it is this which is used to generate the heat. From technical point of view, clothing materials are welded with frequencies in the ultrasonic region of around 20,000 cycles per second. The material to be welded should be at least 65% thermoplastic, though there is scope for welding materials with a high natural fiber content if a plastic film is inserted between the plies being sealed together.
Applications:
The methods described make use of a welding machine working on a ‘plunge’ principle i.e. it welds a limited area or length of material at time.
Typical uses are the application of-motifs to garments:
- Cutting and sealing to length of ribbons and straps
- Shaping of small garment parts, which would otherwise be costly and time consuming to sew.
- Another item which can be usefully cut to exactly right dimensions is the hook and eye tape used as a fastening.
- More substantial operations which could be welded are waistband ends on sports shorts.
- Another use on the same type of garment could be to create a small vent at the lower end of side seam.
Advantages of Welding:
- Welding saves a lot of time and guarantees accuracy of shape in the finished garment parts.
- It is also important as a method of water proofing the seams on garments made from materials rendered waterproof by means of a coating of PVC on the outside. The process of sewing followed by sealing is time-consuming and costly but the garments are designed for high performance protective wear for outdoor situations.
On some materials, a sufficiently strong seam can be achieved after sewing and welding. In either case, the seam becomes bulky and inflexible. Garment design is thus important because of this bulk and cost. Garments of this type normally have a minimum of seams. A neat, non-bulky end is achieved.
Since they are loose fitting garments, the loss of shaping possibilities is not of concern.
Equipment Used:
In addition to stamping and plunge type operations, the welding principle can be used in rotary machines. In this case, a rotating wheel replaces the anvil & if the wheel has a dot pattern on it, an effect similar in appearance to stitching can be created. The garment parts must be conveyed accurately through the machine to obtain correct seam line. This machine is similar to flat bed sewing machine but without thread control systems.
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