Athleisure has opened up a new vista of opportunities along with double-digit growth rate globally and unheard of product categories like spyder tee, muscle stringers, palette bra and biker shorts, to name a few. It is a no-brainer that fabrics used for athleisure and activewear have inbuilt characteristics like stretchability, breathability, moisture wicking, water repellency, etc. But to join these fabrics, the garment also requires special technology to complement the fabric characteristics; for example, stretchable seam for ultra-stretch fabrics, seam sealing or welding for water repellency, seam bonding for flat and thin seam, and so on.
Dr. Prabir Jana from NIFT and Anshuman Dash from H&H discuss the challenges and infrastructure required for manufacturing of athleisure/activewear with special focus on cut and sew type.
Manufacturing of athleisure or activewear consists of some fundamental technology shifts and we come across few new terms like stitchless, seamless, wholegarment, apart from traditional cut and sew process. Traditionally fabrics are joined by thread and needle to make apparel. The technology of joining fabrics without using needle and thread is called stitchless. Circular knitting traditionally creates tubular fabrics, while the same tubular structure is engineered to accommodate 3D shapes as well as variation of fabric construction, to fit human body parts; the same is called seamless.
A seamless garment technically may not have any seam (thus join). Stitchless joining or hybrid joining (combination of sewing and stitchless) of fabrics is recent trend in lingerie, performance sports/ activewear/athleisure apparel and non-apparel products (backpacks, adventure gear, etc.) or even formalwear.
Wholegarment is nothing but a type of seamless knitwear that is produced on SHIMA SEIKI’s WHOLEGARMENT knitting machine. Although seamless products require very negligible or no requirement for joining, the stitchless requires a different set of machineries to join the fabric.
Cutting does not require any specialised machinery and equipment; however due to slippery and stretchable nature of the fabric, extra care is required to be taken. Moreover, as the fibre content is 100 per cent synthetic and often with high thermoplastic content, sealing of the edges should be avoided while cutting. The athleisure and activewear use lot of tapes, films which are ultra-thin in size and require to be cut accurately. Therefore, a laser cutter is mandatory for these units.
These laser cutters should be equipped with in-built camera which can help in accurately cutting different profiles by using direct vision systems. The manufacturer should have basic design software like Adobe to do the necessary. Laser cutting also gives you additional advantage of sealed cut edges of fabric component which does not fray during handling. For multi-layer cutting, die cutting also can be used; but small size are limitations.
Joining of fabric is most challenging and maximum value is added during this stage which are either functional or aesthetic. In a departure from normal cut-n-sew knitwear where superimposed seam by overlock (514 type) is common, the athleisure and activewear are generally joined by overlap seam or butt seam with six thread top and bottom coverstitch (607 type). These also minimise the thickness as well as give flat seam appearance. For hemming neck and armhole finish, mostly three thread flatlock (406 type) is used.
Another specialised stitch type used for selected activewear brands is activeseam, which is a patented stitch type from Merrow giving unprecedented advantages for activewear. According to Merrow, it is the softest, strongest and most beautiful seam available for technical apparel. Activeseam comes in a nearly infinite number of variations from wide to narrow, compact to elongated, 2D or 3D. Most importantly, the sewing thread used in looper should be texturised type which will give comfort to the wearer while keeping the seam thickness less and flat.
In stitchless fabric joining option, seam bonding is a widely used technology available for a range of clothing including athleisure and activewear. Application-wise bonding is used for overlap seam, felling seam, flat and fell seam, butt seam, and numerous aesthetic uses where imagination is the limit. These can be achieved with three types of machines: bonding tape (also called sewfree tape) laying machine, bonding machine and pneumatic flat press machine.
We need to understand these three stages carefully. In the first stage, the tape laying machine simply applies (pastes) the double sided tape (one side covered with carrier or protective layer) to the fabric ply along the seam line with or without trimming the edge.
In the second stage (which is called bonding), the paper cover from the double sided tape is removed (manually) and second ply of fabric is attached to the tape along the seam line. A continuous machine can be used for bonding or manually the same process is done in batch process. After bonding, the seam is treated in hot and cold press where the seam is first cured in high temperature and pressure and then immediately chilled (which is like quenching to adjust the mechanical properties of its original state).
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Accessories for stitchless fabric joining
Unlike needle and sewing thread, the bonding operation requires doublesided adhesive tape (called bonding tape) as a staple consumable for joining two plies. The tapes are currently available by limited manufacturers from US, Italy, Korea and China. Apart from the basic bonding tape, there are seam reinforcement tape, overlay tape, adhesive films and reflective films. The consumption of binding tape is generally equal to the length of the seam; however sometimes, the seam has additional reinforcement tape, overlay tape.
Sewfree tape laydown machine
Tape laying machines are generally post bed to get a clear view of the seam line and also to avoid friction between machine bed and fabric. The bonding tape is released from the tape release mechanism, which has a positive tensioning mechanism or metering devise depending on application. The differential top and bottom roller can regulate the feeding of fabric and tape and both straight and curved seam can be performed. Some of the machines come with convertible platform for ease of movement of fabric. The chute carrying the adhesive tape is heated to pre-heat the tape and the air nozzle heats up the adhesive up to as per desired temperature and the tape is pasted to the fabric.
Tape laying machine can come with edge trimming function (something similar to overlocking), which is necessary to have neat clean alignment of tape along the fabric edge. The edge trimming can be mechanical as well as ultrasonic. Although ultrasonic results in cleaner, unfrayed edges (for thermoplastic fabrics), it is less effective for trimming varying thickness (read along crossover seams). Mechanical edge trimmer works better for varying thickness, although frayed edges can be an issue for some fabrics.
After tape laying, the peeling of the tape and bonding of the second ply is done using this machine. Basically fabric is passed through two heated rollers along with nozzle heating at top and bottom. Peeling process is manual; however arrangement can be done to peel the top layer of the tape continuously during bonding operation.
Both tape laying and bonding operations are very crucial, as these are generally irreversible operations and repair/alterations are not advisable. After peeling of the top layer, the adhesive is exposed and can attract dust, loose fibre from the atmosphere. Therefore, great care should be taken to ensure that bonding with second ply is done immediately after peeling of the top layer from tape. Bonding machine can be fitted with many different attachments to control the overlap amount (in an overlap seam) and felling amount (in felling seam). It is important to note here that attachments are custom designed and not available off the self.
Portable bonding press
Although attaching of the second ply of fabric with the first ply can be done with continuous bonding machine, often such requirements are of shorter length or acute curve and are preferably accomplished by special portable bonding press. There are small narrow irons with very accurate temperature (unlike usual irons) and the heating surface can be flat or roller shaped.
After two layers are joined by double sided binding tape, the seam needs to be pressed in high temperature and pressure, typically at 200+℃. The pressing process finally cures the seam and the joint becomes permanent. There are a variety of press available with varying sizes and shapes of bed. The shape of the bed can be flat, curved or circular depending on the component types to be pressed (very similar to buck pressing concept). Hot and cold type press are preferred as quenching gives superior quality of seam bonding. Typically every press cycle has to go through 20-40 seconds depending on seam requirement. The machine comes with different combinations of features: upper mould and lower mould; both or any one of them can be heated; either upper or lower can move; the mould movement can be vertical or horizontal. There are also double head machines to increase productivity.
These machines come with superior safety features like two hands simultaneously pushing button for activation of safety lever, for all around moving mould. Also they are equipped with chiller box for hot and cold type.
Ultrasonic welding machine
The current use of ultrasonic welding in athleisure and activewear is only limited to butt seam. Two plies of fabrics are joined and trimmed at edge (by ultrasonic welding) and then opened and the joint is strengthened by bonding using a seam reinforcement tape. When two different colour fabrics are joined and seam reinforcement tape is placed on the reverse side, the front appearance is almost like a multi-colour panel.
Sometimes seam reinforcement tape is used in front to enhance aesthetic appearance. It is worth mentioning that ultrasonic welding machines are available with different types of anvil: roller type or presser foot type. Presser foot type anvil is preferred for variety of seam shapes, straight and curves. Although roller type anvil can give wider seam width and decorative seam appearance, such uses are currently limited in athleisure and activewear.
While there are machines used for rainwear and windbreaker type of waterproof or air barrier products, athleisure may not have much use of it. However, it will be wiser to have one of this in the factory, for application in special cases. High frequency welding machine is another example of this special category. This can be used as an alternative to ultrasonic welding for localised joining of components; for example, joining bra straps, etc. The factory also should have label heat press or label printing machine, which will take care of brand and wash care instructions.
Above machinery infrastructure in appropriate proportion will create a self-sustained, state-of-the-art athleisure and activewear manufacturing unit. Apart from these production machineries, there are some basic testing equipment one must keep in-house. As stitchless fabric joining is at nascent stage, all tests are not commonly available with testing houses. Performance testing like hydrostatic test for seam joints, peel bond test should be conducted on any new developments whenever the material or process changes.