Laser is being used in apparel industry from nineteenth century for various garment manufacturing applications. There are several advantages of using laser over the conventional processes in cutting, engraving, embossing, denim fading and other applications. In addition, product damage potential is reduced, no/less consumables are needed and no problem of toxic by-product disposal as found in some processes. Today’s laser equipment is a result of continuous research and development of earlier products, which has undergone several changes. The initial laser systems were cumbersome, hard to run and difficult to maintain. However, the modern laser systems are simpler in operation and maintenance. Furthermore, the earlier systems were involved with more safety issues and needed the gasses to be constantly replenished. The garment manufactures around the globe should take the advantage of laser application in the post multi-fibre agreement regime to make their products more competitive. This review focuses on the technology of laser including various classifications. In addition it includes the applications of laser in garment manufacturing, their potential hazards and health related concerns.
Laser is being used in apparel industry from nineteenth century. Recently, the use of laser in apparel industry is increasing in cutting garment patterns, patterning designer neckties, 3D body scanning, denim fading and engraving leather. The major reasons for wide application of laser in garment industries may be due to reduced cost, flexibility and anti-counterfeiting. For example the artwork of high-end necktie producers are digitally stored rather than physical patterns to lower the theft risk. When needed, the digital patterns are converted into physical samples using lasers. Recently, the application of laser in denim engraving is increasing rapidly for value addition by replacing the traditional denim-distressing technics, which will take the denim segment to a height of sophistication that can never be realised by non-laser methods. The unique nature of the garment manufacturing industry needs laser applications, which combines performance with reduced cost by eliminating the handling systems used in non-laser workstations.
As an all-new process, there are several applications of laser in apparel industry. Laser engraving and cutting technologies now being widely applied in many garment industries, fabric production units, other textile and leather industries. Various applications of laser are discussed in the following section.
Fabric fault detection
When fabric is received at the stores of a garment production unit, the faults in the fabric can be detected with morphological image processing based on laser. Laser-based optical Fourier transform analysis can be used for fault detection in the fabric as the pattern is repeated at regular intervals. The fabric is focused with a laser and the diffraction gratings obtained from the periodicity of longitudinal an transverse threads in the fabric are superimposed. A Fourier lens is used to produce the diffraction pattern of the fabric. A second Fourier lens with same focal In laser cutting a laser is used to cut the fabric into the desired pattern shapes. A very fine laser is focused on to the fabric surface, which increases the temperature substantially and cutting takes place due to vaporization. Normally gas lasers (CO2) are used for cutting of fabric. The cutting machine (Fig. 2) includes a source of laser, a cutting head fitted with mirrors to reflect the laser beam to the cutting line, a computer to control the entire system and a suitable mean for removing the cut parts. The application of inert gases (N2, He) during cutting prevents the charring and removes debris and smoke from the cutting area. Like the mechanical cutting devices, a laser beam does not become blunt and need sharpening. Automatic single ply laser cutters are faster (30–40 m/min) than automatic multiple ply knife cutters (5–12 m/min). However, while cutting multiple plies, knife cutters are faster per garment cut and also cheaper.
The limitation of laser cutting is the number of lays of the fabric that can be cut by the beam. Best result is obtained while cutting single or a few lays, but the accuracy and precision is not obtained with several plies. In addition there is a chance of the cut edges to be fused together especially in case of synthetics. In some cases the sealing of the edges of cut patterns and sewn garment parts is essential to prevent fraying, where the laser plays the role. As in garment production facilities emphasis is given in multiple lay cutting, the laser cutting seems unlikely to become widespread. However, it is successfully used in cutting of sails where single ply cutting is the norm and a slight fusing of the edge of synthetics and woven materials is desirable. In addition, laser cutting is used in some areas of home furnishing.
Laser cutting is cheaper compared with the traditional cutting methods Furthermore, as the laser cutting doesn’t have mechanical action, high precision of the cut components at high cutting speed are feasible. The laser cutters are safer and include simple maintenance features, which can be operated for longer duration. The laser cutters can be integrated to the computer technology. It can produce the products at the same time when designing in the computer. Laser cutting machines have faster speed and simpler operation.
Laser cutting machines are suitable for cutting textile fabrics, composites and leather materials. They can operate for a wide range of fabric, which is not possible with die cutters. Hence, laser cutting machines are gradually been accepted in garment manufacturing. The features of laser applications include: Laser marking, laser engraving and laser cutting combined in one step
- No mechanical wear, hence good quality
- No fixation of material is required due to force-free processing
- No fabric fraying in synthetic fibres due to formation of fused edges
- It is clean and lint-free
- Simple process due to integrated computer design
- High quality raw materials and significant cost saving
- Extremely high precision in cutting contours
- High working speed
- Contactless, wear-free technique
- No chips, less waste
Objective evaluation of seam pucker
Garment appearance greatly influences garment quality. Seam pucker negatively affects the garment appearance. There are several methods to measure seam length magnifies and inverts the test sample image. A charge-coupled device (CCD) camera is used to capture the image. The data is transferred and stored in a computer. The computer programming helps in comparing the acquired images with the stored images by converting the image into binary mode. A fault is reported when the measured parameter is deviating from the standard. The severity of the fault depends upon the amount of deviation from the standard.
After they were introduced in the 19th century, the fashion designers are widely adopting laser cutting in garment manufacturing. In synthetic fabrics, laser cutting produces well-finished edges as the laser melts and fuses the edge, which avoids the problem of fraying produced by conventional knife cutters. Furthermore, use of laser cutting is increasingly used for leather due to the precision of cut components. In fashion accessories such as jewellery, laser cutting can be used to produce new and unusual designs to produce a fusion of apparel design and jewellery style.
pucker, but the conventional rating system developed by American Association of Textile Chemists and Colourists (AATCC) is mainly used. The laser beam can measure the degree of puckering in garments by geometrical models. In this method a seam in the garment is scanned by a 3D laser scanner by putting the garment on a dummy. The laser head can be moved to any 3D space within a confined place by an operator. It is possible to scan the target object from different angles. A pucker profile of the scanned seam can be obtained by processing the image with a 2D digital filter. Physical parameters such as log σ2 (σ is variance) can be obtained from the pucker profile, which can then be linearly related to grade for seam pucker. From the objectively measured log σ2, the pucker grade can be objectively evaluated.
The term mass customization is used when custom-fit garments are obtained depending on the body dimensions and individual’s choice. The very first thing to mass customize garments is the accurate measurements of individual’s body.Lase scanning technology is one of the many techniques used for measurement. Laser scanning technology uses one or multiple thin and sharp stripe lasers to measure body size. Cameras are also used to acquire the scene and assist the laser scanner. The body measurements are derived by applying simple geometrical rules. In order to confirm the harmlessness of the beam, only eye-safe lasers can be used. Additional optical devices such as mirrors can be used to assist a single laser beam. The laser scanning unit (Fig. 3) consisting of light sensors and optical systems focuses on the human body for digitisation. The number of light sensors and optical systems can vary as per the positions of the body. For example, Vitronic1 body scanner consists of three scanning units that can synchronously move vertically along three pillars.
Laser-based denim fading
Now the age of fading of denim by sandblasting is becoming older as the new technology of laser fading is replacing it. In laser fading, a computer drives the laser beam to the material where marking or fading is required. The laser beam decomposes the dye and the resulting vapours are vented away. The material fades only where the beam impacts on the fabric. Commercially two types of lasers are being used: Solid based (wavelength of μm) and gas based (wavelength of 10 μm). The desired degree of fading depends upon the wavelength, power density, and pulse width of the laser beam. The method of marking or fading by laser is more environmental friendly as compared to acid washing or sandblasting.
- High working speed without mechanical contact
- No wear and tear of components
- Reduced waste
- Complete exhaust and filtering
- Exact contours possible
In laser engraving laser is used to mark or engrave an object. The process is very complex, and often computerised systems are used to drive the laser head. In spite of the complexity, very precise and clean engravings can be obtained with high rate of production. The technique does not involve physical contact with the engraving surface, hence, no wear and tear. The marks produced by laser engraving are clean, crisp and permanent. In addition, lasers are faster than other conventional methods used for product imprinting, which provides greater versatility in material selection. One machine can be used to cut through thin materials as well as make engravings on them. Laser engraving is used to engrave the printing screens, for hollowing, for creating pattern buttons, to engrave leather, denim etc. (Fig. 5). Pictures, flower patterns and even personalised signatures can be engraved on leather shoes, leather bag, wallet, leather belt, leather sofa and leather clothes, greatly increasing the added value of products. In addition laser engraving is used to create embroidered pattern in the fabric by colour fading and burning the fabrics. The low cost sealed CO2 lasers are preferred for laser engraving.
Denim engraving is another fast-growing application of laser using sealed CO2 lasers. The laser is used to create minute designs and patterns on denim fabric as well as finished denims. This technic can be used in place of the traditional technique such as sandblasting and acid washing. The accuracy and design flexibility is very wide, which can’t be achieved by the traditional methods. Lasers can produce 3D effects by techniques such as embroidering, embossing, or even apparent cuts, tears and mends. Any image that is created in a computer aided design (CAD), can be transferred to denim by suitable laser process. While using lasers, features such as good mode quality, high power stability, real-time control of laser power and fast pulse rise-time are the important parameters that can lead to colour change without charring or other damage to the fabric. Such damage could reduce the product life and cosmetically unacceptable. The advantages of laser engraving over traditional methods include:
Welded garment production
Welding is an alternative process of joining fabrics for garment production where the thermoplastic materials are joined together by the application of heat. The heat can be supplied by ultrasonic or by high powerful laser. The welded garment though weaker than the sewn counterpart, gives better appearance as it does not contain bulky seam and is more flexible.
Bar code scanning
The scanners used to scan the barcodes for product identification typically uses helium–neon (He–Ne) lasers. The laser beam bounces out of a rotating mirror while scanning the code. This sends a modulated beam to a computer, which contains the product information. Semiconductor based-lasers can also be used for this purpose. However, some of the recent manufacturers are using Radio Frequency Identification (RFID) based tags instead of barcodes due to certain advantages. The RFID tag can be processed quickly and it avoids the physical handling of the product as in barcode systems.
Laser can also be used in marking on various surfaces. The advantages of laser marking include fast, high precision and clear marking on products of varying contour and hardness. It can also be used for a wide range of organic polymers where precession can be obtained even with complex designs. Laser marking is durable and can be applied in clothing, leather and metals. Laser marking is considered to be the best choice for branded clothing and marking fashion accessories during processing.
There are many other applications of laser in apparel industry as discussed below:
- In some stitching machines (e.g., automatic welt pocket attaching machine) laser beam is engaged for automatic and accurate positioning of the welt and to make a slit across the fabric
- In some metal detection machines laser beam is employed to find if any needle part is there in the final finished garment
- Laser-engraving machine can engrave any decoration on the surface layer of any material, making the products looking high grade and exquisite
- Laser technology is gaining impetus in garment finishing which can produce various surface ornamentations without any wet processing. This technique is very accurate and can work fast with good repeatability and reproducibility
- The application of antimicrobial finishes into textiles has significantly improved compared to the past. Laser treatment was used for durable antibacterial properties on cotton fabric using silver nanoparticles