The primary purpose of clothing is comfort of the wearer, a feature which is maximized by the use of bonding and welding technologies. Such machines not only give a pucker-free finish to the seam, compared to sewing technologies but also impart water and air proofing properties to apparels. Through seam sealing even the conventional sewn seams can be upgraded to ones impermeable to water and air. Carrying forward its commitment to keep the industry informed with its in-depth analyses of technology and management in the sewn product industry, StitchWorld has taken upon itself to guide the industry on new opportunities originating from welding and bonding techniques for various products such as outerwear, outdoor gear, tents and footwear besides apparels. In this article, Team StitchWorld discusses the ultrasonic welding and bonding technologies from Hong Kong-based H&H.
With more than two decades of experience in manufacturing welding and bonding machines, H&H has developed a range of solutions for bonding, ultrasonic welding and pressing. While the AI series of machines are suitable for sealing of the already furnished seams, regardless of how the seam has been made – sewing, bonding or welding; SF series of machines are specifically designed for tape laydown operation on straight and curved seams of 2D and 3D constructions.The US series machines for ultrasonic welding of thermoplastic materials and the CS series of machines for fixing the bonded seams.
Hot Air Sealing Machines
Seam sealing proves to be advantageous mainly in products that are supposed to be waterproof as a sealed seam does not allow water to pass through it. The H&H hot air sealing machines use tape to seal the seam. The seam that is to be sealed is made to pass through the machine in-between two differential speed top and bottom rollers. The top roller pulls tape from the roll and sticks it on to the seam so that it can be sealed. A nozzle placed along with these rollers blows hot air on to the seam that is being taped which melts the glue of the tape so that it can be glued properly on to the seam. The seam which then comes out from the other side is sealed properly. There are three models being currently offered under the AI series, viz. AI 001, AI 007, and AI 008.
The AI 001 sports a special feature, the 3D electronic nozzle positioning system which helps in positioning the nozzle in such a way that the material does not get burnt, as it varies according to the usage of the operator. It also offers variable speed seam sealing which helps when dealing with curves as one can lower the speed at curves and increase it again for straight seams. Both the hardware and software of this machine are upgradable. The AI 007 offers a duplex nozzle action which, rather than providing a simple straight line path, provides a combination of two straight lines which helps in generating a more even heating effect on the seam tape. The cheapest of the AI series is the AI 008 machine which comes with a single nozzle system and a digital pressure gauge which helps in measuring the pressure of the rollers in easy units unlike reading it from the analog pressure gauges. Though the recommended pressure for the rollers is 4-6 bars, the pressure needs to be increased with increase in the thickness of the fabric layer.
The tapes used are also of different types, like single layer and three-layer seam tape for waterproofing, seam reinforce tape (SRT) for sew-free construction, overlay tape (OT) for decoration, etc. The AI 001 makes possible three-layer seam sealing designed for thick or heavy duty materials used in rainwear, wind breaker, ski jacket, tent and sleeping bag. The machine is 30% faster and consumes 5% less tape than its competitors as the traditional seam sealing machine can utilize only around 95% of tape as the initial 5% gets wasted, but the AI series has a special ‘tape start’ program which helps in utilizing 100% tape.
“As Sewfree tape laydown machines are used for both cotton and thermoplastic fabrics, ideally the machines should have a flexible option of using a dual trimmer; while the mechanical action trimmer is good for cotton fabric, the ultrasonic trimming is ideal for thermoplastic fabrics. Current machines are available with either of the options.” – Prof. Prabir Jana
Sewfree Tape Laydown Machine
The SF series or the Sewfree tape laydown + trimmer machine offered by H&H allows precise seam making using tape. It uses a mechanical high-speed knife to trim the fabric edge, but future SF models will have ultrasonic trimming which will provide an anti-fraying cut edge. There’s currently only one model under this series, the SF 013, which is used to lay down tape on one edge of the material and trim the edge alongside, giving it a precise seam edge. Hot air is blown on the tape using a nozzle in this machine as well. After peeling off the upper cover layer of the tape, the other part is placed on top of this taped material to form a seam. Due to the usage of ultrasonic energy, fraying and accumulation of material in the seam does not happen, resulting in a cleaner and thinner seam.
The seam prepared in this manner is then taken to a hot & cool pressing machine or to a hot air sealing machine to fix the seam permanently. With a maximum sealing speed of 30 feet per minute, the machine comes with a convertible platform which makes it easy to deal with different complex structures, and offers differential speed top and bottom rollers. Working on 2D as well as 3D construction is easy with this machine and both straight and curved seams can be obtained from it. The speed of the cutter is also adjustable.
Ultrasonic Welding Machines
The US series offered by H&H is specifically for the purpose of welding and only one model is currently available under the same – US 501. The US 501 – Sewfree Ultrasonic Multi-purpose Welder helps in welding of two layers of material using ultrasonic energy. The heat produced due to friction between the fibres because of the high frequency ultrasonic energy makes the fibres melt and fuse together to form a seam. It results in a precise seam as the extra material is cut off by the trimmer, leaving extremely narrow allowance, and the edges do not fray as they get fused with each other. Materials made purely with natural fibres cannot be welded as they would get burnt and hence some amount of synthetic fibres (thermoplastic fibres) is required to be present in the material.
Both, straight and curved seams can be easily constructed using this machine. After making seams from this machine, they need to be sealed, which can be done using the AI series machines. The US 501 also indicates the status of the ultrasonic system, as it can be adjusted according to the material. Materials with higher thermoplastic content can be welded at a lower temperature, hence require lower ultrasonic energy.
Hot & Cold Pressing Machines
The CS series of machines by H&H are used for the pressing function, to fix the bonded seams. Most of these machines are PLC controlled and use high temperature and pressure to fix the bonded seams properly. The temperature and pressure of these machines can be controlled according to the requirement of the material and glue. If excessive pressure or temperature is applied, then the glue can melt, resulting in displacing of the material layers and if the pressure or temperature is lower than required, then the fixing of the seam wouldn’t be proper. Currently a total of 24 models are on offer by H&H under this range, out of which three models – CS 658, CS 661 and CS 663 – are pneumatic cool + heat press machines which offer the special feature of cooling. Cooling is required when the glue that has been used for bonding has a lower melting point. Such glues melt easily and hence cooling is required to dry them so that they get fixed properly and do not get displaced. These machines offer a temperature range of room temperature to 260° Celsius, pressure range of 0.2 to 2.4 kg/cm2 and a time range of 1-999 seconds.
Specialized heat press machines are also offered in this range for dealing with curved seams, cuffs, sleeves, and zippers. The CS 651 is an automatic cuff press machine which can press two cuffs at the same time. It has separate control for the left and right cuffs and the rotating action can be digitally controlled. The CS 660 pneumatic flat press machine features two lower moulds for left and right sleeve operations. The CS 667 pneumatic curve press machine is specially designed with a curved base to negotiate curved seams properly to avoid puckering. The CS 681 pneumatic zipper press machine has been designed especially for zippers. And lastly, the CS 671 manual flat press machine is the only one in the range which has to be operated manually unlike the others which are controlled pneumatically.
