Regardless of which fusible and machine are used, fusing is controlled by four processing components-temperature, time,pressure and cooling and these have to be accurately combined in order to achieve the optimum results.
Temperature: There is a limited range of temperature that are effective for each type of resin. Too high a temperature causes the resin to become too viscous, which force the resin to the inside of cloth. If the temperature is too low, the resin is not sufficiently viscous to disburse into the top cloth. The resin-melt temperature range from 130-160 degree Celsius and best results normally occur within + or – 7 degree Celsius.
Time:The only time element of any value during the fusing process is when the top cloth and fusible are under pressure in the heating zone of the machine. This time cycle for a particular fusible is determined by:
Whether the fusible has a high or low-melt resin
If a light or heavy substrate is being used
The nature of top cloth being used, i.e. thick or thin, dense or open.
Pressure: When the resin is viscous, pressure is applied to the top cloth and fusible assembly to ensure that:
Full contact is made between top cloth and fusible
Heat transfer is at the optimum level
There is an even penetration of the viscous resin into the fibers of top cloth.
Most fusing machines use two steel rollers or pressure plates to create pressure, but a flexible pressure system has been developed which automatically adapts itself to variations in thickness of assembly being fused.
Cooling: Enforced cooling is used so that the fused assemblies can be handled immediately after fusing. Cooling can be induced by various systems, including water-cooled plates, compressed air circulation and vacuum. Rapidly cooling the fused assemblies to 30-35 degree Celsius makes a higher level of productivity rather than to wait for cool naturally.
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