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 (Choudhury and Shirley 2010; Nayak and Khandual 2010). Various applications of laser are discussed in the following section.
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 (Mallik-Goswami and Datta 2000; Ribolzi et al. 1993; Mursalin et al. 2005). 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 and 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 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 (Petrak and Rogale 2001). 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.
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 (Mahrle and Beyer 2009). Furthermore, as the laser cutting doesn’t have mechanical action, high precision of the cut components at high cutting speed are feasible (Mathew et al. 1999). 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 lather materials (Caprino and Tagliaferri 1988; Steen et al. 2010; Cenna and Mathew 2002). 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:
Garment appearance greatly influences garment quality. Seam pucker negatively affects the garment appearance (Nayak and Padhye 2014b, 2015a; Nayak et al. 2010, 2013; Fan and Liu 2000). There are several methods to measure seam 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 (Nayak and Padhye et al. 2015a). Laser 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 (D’Apuzzo 2007; Tong et al. 2012; Ashdown et al. 2004). 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.
Now the age of fading of denim by sandblasting is becoming older as the new technology of laser fading is replacing it (Ortiz-Morales et al. 2003; Tarhan and Sarıışık 2009). 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 vapors 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 1 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 (Kan et al. 2010). A laser-faded denim sample is shown in the Fig. 4.
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 (Kan et al. 2010; Juciene et al. 2013). 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 personalized 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 (Juciene et al. 2013; Kan 2014a). 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 techniques 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:
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 (Petrie 2015). The welded garment though weaker than the sewn counterpart, gives better appearance as it does not contain bulky seam and is more flexible.
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 (Nayak and Padhye 2014c). The RFID tag can be processed quickly and it avoids the physical handling of the product as in barcode systems (Nayak et al. 2007, Nayak et al. 2015b; Nayak and Padhye 2015b). The mechanism of a bar code scanner is shown in Fig. 6.
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: