The heat setting machine is suitable for the processing of various knitted fabrics. Its main function is tenter drying. Through the longitudinal overfeeding and transverse tenting of the needle clip chain of the heat setting machine, the shape of the fabric can be adjusted and the longitudinal shrinkage of the fabric can be reduced. According to the different types of fabrics processed, in addition to the different process flows and conditions implemented, the configuration of the heat setting machine should also be different, including the configuration of the heat setting machine itself and the configuration of the unit equipment related to it.
Reasonable configuration can simplify, rationalize and save energy the drying and heat setting process of the heat setting machine, avoid adverse phenomena caused by improper implementation of the process, and improve product quality.
Preheating and shaping effectively relieves fabric wrinkles
The heat setting process arrangement for polyester, nylon, acrylic and other synthetic fibers and their blended interwoven knitted fabrics and elastic knitted fabrics containing spandex has two forms: preheating setting and post heat setting.
Preheating and setting refers to the preheating and setting of gray fabrics and the heat setting of semi-finished products that have been relaxed, bleached but not dyed or printed. Post-heat setting is a finishing process with the purpose of ensuring good dimensional stability of end products in dyeing and finishing plants and overcoming undesirable phenomena that occur during subsequent processing.
Heat setting will change the crystal structure of polyester, nylon and other synthetic fibers. The crystal structure of polyester fiber changes before and after heat setting. Changes in fiber microstructure will inevitably change the dyeing properties of the fiber. Normal preheating and setting will mostly reduce the color yield of the fiber.
If the heat setting process is not properly controlled, the following dyeing problems will occur: If there is a temperature difference between the left, center and right in the heating zone of the heat setting machine, a color difference between the left, center and right will occur. The higher the temperature set in the heat setting process, the greater the temperature difference between the left, center and right. It may be bigger: If there is a difference in air jet volume between the upper and lower air outlets of the heating area of the heat setting machine, the “yin and yang side” phenomenon in dyeing will occur: if the fabric moisture content is large or the fabric liquid content is uneven, it will enter high temperature setting Area, it is easy to have poor dyeing, color flowers and “yin and yang” phenomena: if the external force on the fabric during heat setting is not hooked, such as excessive transverse stretching and excessive longitudinal superabsorption, etc., it will cause longitudinal dyeing. and horizontal stripes.
If the fabric is not preheated and set, excessive dimensional changes and fabric wrinkles will not easily occur during the bleaching and dyeing processes, or even if they occur, they can be completely overcome by post-finishing, there is no need to preheat and set. Whether to perform preheating and setting and what conditions to use for preheating and setting need to be determined through experiments.
The heat setting machine and its related configuration unit equipment used in dyeing and finishing plants include centering devices, overfeeding needles, needle clip chain extension, heating areas, cold air cooling, cold water roller cooling, and cloth feeding and dropping. This is heat setting The basic structural part of the machine, the padding machine is the unit machine configured with it.
The biggest difference in the basic structural configuration of the heat setting machine is that the stretching width of the needle clip chain in the heating zone is “fixed” or “variable”.
The fixed type means that the fabric passes through all heating zones with a fixed width, and the variable type means that the width of each heating zone that the fabric passes through is adjustable. Varieties such as warp knitted fabrics that need to be narrowed in width after preheating and setting require the use of variable heat setting machines. Some warp knitted or weft knitted fabrics that have a larger width shrinkage after relaxation and bleaching are also best to use variable heat setting machines. Variant heat setting machine.
The relevant configuration units of the preheating and shaping machine include padding machines and pre-drying machines. The padding machine is generally a two-roller padding machine. It is mostly used for hot pre-shaping of fabrics after relaxation, scouring and bleaching before dyeing. Sometimes it is also used for fibers with many wrinkles on the cloth surface due to improper storage methods and other reasons. Water rolling for pre-shaping of plain fiber/spandex fabric gray cloth. When preheating and setting pre-dyed semi-finished products that do not contain wet gray fabric or have been dried, the cloth threading route only needs to pass through the padding car, which can reduce the tensile tension of the fabric, save energy and reduce wear and tear on the equipment.
After rolling water in the pre-drying machine, it should be pre-dried at a lower temperature before high-temperature heat setting. There are two ways to pre-dry. One is to adjust the temperature of the heating zone of the heat setting machine itself from low to high. The other is to install a special dryer before the needle device of the heat setting machine, such as in the padding machine. , a double-layer oscillating dryer is installed above the position of overfeeding needle and needle wedge extension.
Simplified post-heat setting process in various forms
Polyester, nylon, acrylic and other synthetic fibers and their blended interwoven fabrics, regardless of whether they have undergone preheating and setting, as long as they undergo high-temperature heat treatment again, the shape of the fabric will be deformed due to the thermal shrinkage and thermoplastic stretching of the fibers, and the fabric will be deformed due to the thermal shrinkage and thermoplastic stretching of the fibers. Wrinkles and creases are caused by the stretching and squeezing of irregular external forces.
The measure to overcome these fabric deformations is through post-finishing heat setting, which is referred to as post-heat setting. Of course, good preheat setting can make post-heat setting of the fabric easier, but it needs to be emphasized that the role of post-heat setting is not only to overcome the bad shape of the fabric that has been formed in the previous process, but more importantly. It is to make the fabric meet the dimensional stability requirements of some subsequent processing steps, such as high-temperature steaming during re-printing after dyeing.The electric energy accounts for a considerable proportion. The higher the drying temperature and the faster the vehicle speed, the less electric energy consumption will be. However, excessive drying temperature and the high-temperature steam generated will cause some fiber cones to turn yellow and strong. The decrease will aggravate the thermal migration of disperse dyes and reduce the dye fastness, which will affect the vertical effect of polyester, fine fiber and other thread fabrics. Therefore, the drying temperature must be determined based on many factors such as the properties of the fibers in the fabric, fabric style requirements, and dye properties.
Generally speaking, the use of hot air stenter setting machine in the dyeing and finishing processing of knitted fabrics is diverse. It can be used for preheating and setting of gray fabrics, pre-dyeing heat setting and post-finishing heat setting of thermoplastic fiber fabrics. It can be used for various fiber fabrics. Drying can also be used for paint printing, coating, and baking for waterproof and oil-proof finishing; many knitted products have to go through a heat setting machine multiple times for drying and heat setting, sometimes for real heat setting of thermoplastic fibers. , sometimes just tenter drying. Although the same heat setting machine is used for different purposes, the process flow and conditions are different. Gray fabric preheating and setting, preheating and setting before dyeing, finishing heat setting and hanging drying all have their own processes. Require.
The heat setting machine can undertake processes such as drying, preheating and post-heat setting. In addition to the quality of the processed products being closely related to the configuration of the heat setting machine itself, other related configuration units such as padding machines, pre-dryers, steam Wetting devices, brushing rollers, etc. also play an important role. A well-configured overall production line can make the production process scientific, simple and energy-saving.
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