Fusing

y . Why Fusing? y Fusing is done to achieve any one or multiple of the y y y y y

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following objectives in a garment or made ups: Improve dimensional stability & shape retention / crease recovery property of outer fabric Improve aesthetic value, appearance and handle of fused part. Value addition to the garment Reduce stitch puckering & increase seam strength. Valuable aid in production for eliminating some stitching operation & better reliability of reproducing consistent good quality. Increased ease of handling, faster & better production

y I) the fusing methods; y II) the fusing machine y III) the components of fusing.

Fusing Method:y The relationship between the top-cloth and the fusible influences the fusing conditions, and it is essential that the press can achieve the correct combination for the particular method employed. The most widely used methods are described in terms of the assembly of the cloth and fusible components prior to fusing y Single Fusing: The fusible is positioned on top of the cloth. y Reverse Fusing: The cloth is positioned on top of the fusible. y Sandwich Fusing: Here, two components are fused in one operation, typically with the cloth on the outside and the two fusibles in the middle. y Double Fusing: This consists of fusing two fusibles, positioned one on top of the other, to the top-cloth in one operation, for example, fusing the front and chest-piece fusible to the fore part of a jacket or coat.

Fusing Machines:y The mechanical medium required for fusing is the fusing press. Presses basically fall into two categories, with different modes of operation. The assemblies are either fused on discontinuous systems or on continuous conveyor type systems. y Discontinuous Systems: y Hand Iron: This system effects fusing by placing a hand iron on top of the assembly to be fused (interlining uppermost) which is supported by an ironing table. Certain interlinings, especially those that can be fused at comparatively low temperatures, low pressure and short times, may be suitable for fusing by hand iron.

DISADVANTAGESy Compared with a fusing press the hand iron has

several disadvantagesy Temperature control and distribution over the heated surface is poor and temperature difference can be large. y Due to the lightweight and small surface area of the iron and the iron and the hand-applied pressure, it is impossible to measure and apply pressure uniformly. y Time has to be controlled manually.

y Flat bed Fusing Machine: These systems effect fusing by

placing the assembly to be fused on metal plates, one or both of which can be heated. In a typical flat bed press the upper plate is electrically heated and unpadded, whereas the bottom platen is unheated and padded with a resilient cover of wool, felt or silicone. Top and bottom bucks can be covered with a PTFE (Poly Tetra Fluoro Ethylene) cover to prevent staining, adhesive build up, adhesion of garment parts to the buck and assist in maintaining a clean surface. Heat is provided by an electric heater element embedded in the pressure plate. The heating element must be such that an accurate and uniform distribution of the temperature is obtained over the plate surface. Closing the plates provides pressure together by pneumatic, mechanical or hydraulic means. Pressure must be applied accurately and uniformly and it is important that the pressure system is free from possible distortion, either from mechanical effects or by heat. The upper and lower plates must join perfectly together when pressure is applied. There are three basic types of flat bed fusing machine namely scissor action, vertical action

y An automatic timer is generally provided which controls the pressing y y y y

cycle. In some cases the opening and closing time is also included in the cycle. An improvement in flat bed presses is the tray system where, the assemblies are either made up on the press tray or brought to the tray pre-prepared. the tray is then pushed or powered to its fussing position. when the fusing cycle is completed, the tray can be manually removed or automatically rejected. Flat bed presses with twin-tray systems are considerably more productive than those with single-tray systems because the time lag caused by waiting for the fusing cycle to end is considerably reduced. The main advantage of the twin-tray system is that, while one tray is being fused, the other can be stripped and loaded. Another type of flat bed press is incorporated into carousal by using three trays that successively move through the loading, fusing, and cooling stations.

Continuous Systemsy These fusing machines are all based on the same

principle, hereby the unit for fusing is transported through the fusing processes by means of a powered conveyor belt. There are two systems in general use, return feed and end-to-end feed

Heating Mechanismy Heating plates: These consist of two heating surfaces, positioned apart, with

one above the conveyor belt and one below the conveyor belt. The surfaces are slightly arched so as to intensify the heat diffusion. The lower heating surface is usually longer than the upper, and, in relation to the conveyor direction, the lower heat source is positioned after the higher one. Both panels can be separately controlled, which enables any temperature profiles to be achieved. There can be series of upper and lower heaters, which can create different heat zones. y Cylinder heating: The cylinder consists of two parts, the inner cylinder, a stationary assembly in which the heating element are mounted; the outer cylinder, which rotates around the inner cylinder. This principle ensures that the heat generated by the inner core is evenly distributed all over the cylinder mantle. Since approximately half of the cylinder-mantle surface area is in the actual heating zone at any given moment, the remaining area regains the heat lost through transference. These types of machines generally have a preheating device located under the lower conveyor belt, between the entry zone and cylinder.

Pressure:y Pressure: With the drum/belt presses, minimal pressure is applied continuously from the point of entry by the belt tension against the drum or between two conveyors. Thus pressure is applied at all times during the heating up process until the assembly leaves the press. This minimal pressure is necessary to avoid slippage between interlining and upper fabric. Adequate control of the belt tension across the width is essential to ensure even pressure. With conveyor type presses the actual pressure is applied by rollers to the previously heated assembly, at the outlet of the press. Since pressure is applied as a line pressure at the contact of the two rollers, the time is very small compared with flat bed presses and thus the pressures required are different and the pressing can be more critical.

y Fusing time depends on the speed on the conveyor

belt, the faster the belt runs, the shorter the time. All machines have a belt speed controller which can be adjusted to give various dwell times in the heated zone.

Return feed:y This conveyor system is, in effect, one upper and one lower drum surface,

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where the drum is the actual conveyor of the cloth and fusibles. The function of the upper or cover belt is to ensure that both cloth and fusibles are held accurately in the correct positions while being transported through the fusing processes. While the drum is positively driven, the speed of both (the drum and the conveyor) must be synchronised in order to prevent the compression or extension of the materials. Belt Cleaner: Continuously cleans the belt from adhesive contamination Belt wrapping prevention device: Adjust belt tension and avoids belts from wrapping. Pressure Roller: Apply actual pressure at roller nip point. Rotary strip-off device: After fusing the fused composites tends to stick to the drum, this device strips of the fused composites from the drum. Drum cleaner: Continuously cleans the drum from adhesive contamination Teflon Belt: Woven belt made out of Kevlar fibre, coated with teflon.

Drum continuous fusing machine:Drum continuous fusing machine: Completely closed chamber, no heat loss. Gradual heating not available, chances of heat shock1 No compensating heater, thickness variation of interlining composites may result unsatisfactory fusing. y Comparatively cheaper (than flat continuous fusing machine) y The interlining composite travels through the fusing zone, the travel path is not horizontal rather curve, so there are chances of distortion during travel. y The interlining composite travels through the fusing zone, chances of distortion during feedingy y y y

y End-to-end feed:

The parts are conveyed from the loading area at one end of the machine, via the fusing area, to the take-off area at the opposite end of the machine. This system is used where production levels require continuous loading and feeding on the parts of the operators.

TEMPERATUREy

Fusible interlinings are coated with specially formulated thermoplastic adhesives of various types, e.g. either LDPE or HDPE. Each type has its own individual characteristics but generally speaking the adhesive must be heated to a point within a minimum and maximum temperature to ensure optimum performance. For a good quality fusible interlining the glue-line temperature is generally mentioned. If this temperature is not reached fusing will not take place and if it is exceeded problems of strike back, adhesive migration and low bond strength can be experienced. It is the temperature at the adhesive layer that is critical, i.e. the Interface Temperature or glue-line temperature . It is important that in every fusing operation the fusible achieves this temperature. It is possible to take measurements of the glue-line temperature but it is more common to use the dial temperature and by experience adjust this to obtain the necessary temperature at the interface. The temperature setting on the press is normally kept 10-150 higher than the glue line temperature specified to account for loss of heat in transfer & ensure correct melting pt of adhesive. Normally temperature is automatically controlled by reliable / efficient thermostats within 3% - 5% range.

y Resin :Resin Polethylene y low and medium density, y wash and wear , y drycleanable Polyamidesy higher melting range y dry cleanableand washable till 60C y Dry clean only PVC-Siliconised rainwear Polyester-

fusing temp-120-65C,washable,drycleanable Resin blends

y Causes of uneven temperature: Uneven

temperature in a press may not be solely due to the quality of the thermostats fitted. Two other factors that influence temperature are: y The type of heating elements used and their position in the heated areas of the press. y In flat-bed presses the very opening and closing of the press allows hot air to escape and cold air to enter resulting heat loss. Even in continuous fusing presses where this heat loss is much less, some still occurs

TIME of this time element is to compensate for the delay y The functiony

y y y y

in the transmission of heat from the source to the fusible agent. It is simply the time duration the composite should be exposed to heat. This time component relates to The time when the two plates of the press actually meet with the correct specific pressure, or the time for which the assemblies are actually in the heating zone if a continuous machine is employed. The type of interlining being used i.e. whether it has a low or high melt adhesive system, or if it has a light or heavy weight substrate. The type of application for which the fusible is to be used - i.e. small or large areas in a garment. The nature of the shell fabric(s) being fused. The type of fusing equipment employed

Pressure:y It is necessary to apply pressure to the parts being fused to ensure; y Intimate contact is effected between the fusible interlining and the

shell fabric. y Adequate heat transfer takes place y Controlled even penetration of the adhesive into the fibers of the shell fabric. y Pressure is normally applied via plates/bucks. The energy to do this is normally supplied by pneumatic, hydraulic or manual sources and transferred to the pressure surfaces by means of cylinders or mechanical linkages. For a good quality fusible interlining the required pressure to be applied is generally mentioned.y y Depending upon the viscons / flow property of glue the pressure is

recommended. Pressure is applied in fusing press mechanically or pneumatically. It is also decide by the structure / surface property of other fabric.

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y 2.4. Sequence of process parameters for correct fusing process: y Satisfactory fusing depends on the application of three basic parameters in correct sequence Temperature, Pressure & Time. All these parameters are required in certain limited combinations & should be adequately controlled. y First heat should be applied for certain time to raise the temperature of interlining-fabric composite to glue-line temperature and then the pressure is applied to enable the adhesive dots of interlining penetrate the base fabric. Heat and pressure should not be applied together as this may result flattening of adhesive dots, resulting unnecessary stiffness in the fused fabric due to increasing area of contact (fusing area) between fabric and interlining. Flattening of adhesive dots also result less penetration of adhesive onto the base fabric thus reduced peel-bond strength.

y Heat Shock y When the interlining-fabric composite enters the

fusing zone then the composite is suddenly subjected to very high temperature, i.e. from room temperature to almost 1400c. This sudden change of temperature (heat shock) harms certain fabrics like viscose etc. This heat shock does not result any visual or immediate damage to fabric composite, but make the fibre brittle and may even change the texture of fabric.

Interlining :y An interlining is a material (substrate) onto which the

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thermoplastic resin is coated, sprayed, or printed. Substrates can be produced in a variety of woven, knitted, and nonwoven forms, each type having a specific application, according to the planned end-use. The base cloth influences the following characteristics in the finished garment: handle and bulk shape retention shrinkage control crease-recovery appearance in wear appearance after dry-cleaning or washing durability

Glue Line Temperature

y While talking about melting point temperature in

fusing we always mention about glueline temperature. This is the temperature which is the minimum threshold range required for melting the glue (based on the melting point of the adhesive). It is therefore the temperature existing at the interface of outer fabric & interlining i.e. contact point of glue & outer fabric. It is checked by using a thermopaper strip. These are chemically coated paper. Which are heat sensitive & displays colour range by change of colour.

METHODS OF APPLYING RESINy SCATTER y Even scatter under automatic control by machines on

substrate .resin softened in oven and pressed . y Cheap but not even and flexibley y y y y

DRY DOT COATING Roller with engraved holes .Resin sticks to cloth . Oven heated roller moves on cloth Lighter weight fabric smaller dots Requires good penetration of adhesive

y PASTE COATING y Fine resins are blended with water and forms smooth

paste y Printed on fabric y Heat removes watery Type of resins y Polyethylene,Polypropylene.Polyesters, y Polyvinyle chloride,(pvc) Plasticised polyvinyle

acetate(pva)

y Base cloth (substrates) :Base cloth (substrates) The

y y y y y

interlining material on to which the thermoplastic resin is coated, printed or sprayed Influences Handle bulk Shape retention Shrinkage control Crease recovery Appearance in wear Durability .

y Woven Interlining ,Knitted Interlining ,Non woven

interlining y Non woven interlining : y Fibres -Viscose, Nylon, Polyester, Acrylic Web

y Coating system : y Process of depositing thermoplastic resin on substrate. y Resin powder is seivedand designated by microns(one

millionth of meter) y Coating methods- Paste coating(up to 80 m) y Dry dot printing (80-200 m) y Scatter coating(150-350 m)