Factors affecting the quality of sanding finishing
There are many factors that affect the quality of sanding, and the relationship is complex, such as the tissue specifications of the fabric, processing technology, The size of the abrasive grains on the grinding roller (the mesh number of the sanding skin), the speed of the sanding roller, the gap between the fabric and the sanding roller, the covering angle, the tension of the fabric on the machine and the moisture content of the fabric, etc., will all affect the sanding effect. In addition, the mechanical properties of fabrics will also undergo corresponding changes after sanding, such as increased softness, decreased breaking strength and tearing strength, etc. The most prominent one is the contradiction between the sanding effect and the decrease in fabric strength.
1. Requirements for semi-finished products of brushed fabrics
Previous The quality of the treatment directly affects the sanding effect and the feel of the fabric, so it requires clean desizing and thorough scouring, and the weight reduction rate is controlled at 1%-2% (consistent before and after); the cloth surface must be smooth to avoid wrinkles, no needle clips, Cloth clip printing; higher requirements for gray fabrics, less roving neps; uniform dyeing, no color difference between left, center, right, front and back, front and back.
It is best to roll the fabric into a large roll before sanding to ensure that the fabric is flat and the rolling tension should not be too high to avoid seam marks; if the fabric box is dropped, drying is required. Grind with a joint machine to remove creases. Softening treatment is required before sanding, which can reduce the friction coefficient between fibers (reduce the cohesion between fibers) and facilitate the formation of fuzz on the fiber surface during sanding. Guangdong Innovation Fine Chemical Raising Softener SD-3175 can be used. High-temperature setting should be avoided before sanding, otherwise the fabric will become tight and hard, resulting in difficulty in raising. If there are wrinkles on the cloth surface, a drying and grinding machine or low-temperature setting can be used.
When processing dark-colored varieties, due to the gradient of dye concentration between the surface layer and the inner layer of the fabric, once the fabric surface has poor flatness and has thick warps, thick wefts, and many neps, After the fabric is sanded, white spots appear in the convex areas. Therefore, the process of grinding first and then dyeing can be used for dark-colored varieties, which is beneficial to the bright color of the suede surface, with small color difference between the front and back sides, making it easy to check the shade, and can prevent the piles of different colors from raising when they are then sanded after dyeing. Contaminate each other. For medium and light-colored varieties, the process of dyeing first and then grinding can be used, such as blended fabrics and fabrics with adhesion tendencies. The raising process should be carried out after dyeing, otherwise the fabric will easily cause difficulty due to sticking during the dyeing process. Eliminates wrinkles and is not conducive to leveling.
2. Influence of fabric structure specifications and requirements for sand leather mesh number
Different fabric tissue specifications have different sanding process conditions. During sanding, the weft yarn is grinded by the abrasive grains at 90°, while the warp yarn is only subjected to the balancing effect of the abrasive grains at 180°, so the damage to the breaking strength of the weft yarn is relatively greater than that of the warp yarn.
If the warp and weft yarn densities of the plain weave fabric are close, the probability of the warp and weft being ground during sanding is equal. Since the abrasive grains cause great wear on the weft yarns, it is advisable to use a finer grained grinder. grains, and at the same time, the fabric tension should be small, so that the contact with the sanding roller is lighter; if the warp density of the plain fabric is higher than the weft density, the grinding effect will be smaller, and the contact opportunities between the weft yarns and the abrasive grains will be less, so as to obtain better To achieve the best sanding effect, it is better to use coarser abrasive grains.
The disadvantage of plain weave fabric is that the interweaving points are easily exposed; the structure of satin weave fabric is relatively loose and prone to lint and snagging; the twill fabric is prone to produce a sense of yin and yang due to uneven warp and weft. The yarn twist and density will also affect the sanding effect. Fabrics with high twist and high density are difficult to sand; thin fabrics will cause strong damage and cause weft movement; medium-thick fabrics have many exposed points in the weft direction and have better sanding effects (even and dense fluff). Therefore, for fabrics with different tissue specifications and yarn count densities, sanding leather with different mesh numbers should be selected to ensure the sanding quality.
Table 1 shows the technical parameters of various types of brushed fabrics produced by a printing and dyeing factory for reference. Table 2 shows the parameters of single-sided plain weave pure polyester produced by a satin dyeing factory
Table 1 The mesh number of sand leather selected for fabrics with different weave specifications
Table 2 The number of sand leather meshes selected for different fabric densities
The fabric relies on the sharp edges of abrasive particles to cut fibers. Therefore, under the same conditions, abrasive grains of different sizes have a great influence on the sanding effect. The abrasive particles are coarse, the hair is long and fast, but the drop is strong; the particles are fine, the hair is short and dense, the hand feels good, and the drop is small. Therefore, light and thin fabrics should use high mesh sand leather; thick and thick fabrics should use low mesh sand leather.
3. The influence of balance between grinding roller speed and fabric running speed
4. Influence of fabric tension and contact degree between fabric and grinding roller
Indication of fabric tension The tightness of the fabric in contact with the grinding roller. The degree of contact indicates the size of the covering angle when the fabric contacts the sanding roller. The covering angle has a great influence on the sanding effect and strength of the fabric. If the contact area between the fabric and the grinding roller is large, the covering angle will be large, the tension will be large, and the sanding effect will be good, but the strength drop will be greater; otherwise, the effect will be poor and the strength drop will be small.
The total arc length (covering angle) of the pressure roller contact of the sanding roller is 150mm~170mm, 0~3 grids are unloaded, and 3~10 grids are loaded. part, each grid represents 25mm���Cause the drying cylinder to break loosely.
Solution: The mercerizing machine repairs the crescent folds and clipped folds of semi-finished products, the folds of the drying cylinder edge suction device, etc. The tenter can be repaired on the tenter frame.
06 Poor sanding effect
Cause: semi-finished product feel It is hard, the cloth surface has poor penetration effect, the tension is small, the vehicle speed is fast, the old sand leather has been used for a long time, the DC motor speed is unstable and the cloth is damp.
Solution: Notify the pre-treatment repair or apply softener, tighten the chain shaft tension, slow down, increase the pressure, replace with new sandpaper and fully dry the cloth surface.
07 Grinding Willow
Cause: Sandpaper seams overlap, The sandpaper rotates in the same direction, threads are wrapped around the grinding roller, and the sandpaper joints are marked or damaged.
Solution: Tighten the sandpaper again, change the direction of rotation of the sandpaper, adjust left and right, and clean the grinding roller thread on.
08 Gross difference between left, middle and right
Cause: left and right pressure The cloth roller is unbalanced, the sandpaper has been used for a long time, and the sand grains in the edges are worn to varying degrees.
Solution: Adjust the balance roller to make the left and right balance consistent, and replace with new sandpaper to solve the problem of the gap between the two sides when changing from narrow width to wide width.
09 Poor strength
Cause: The fabric yarn is thin, The sandpaper has a low mesh number, strong force, high pressure, and slow speed.
Solution: Replace high-grit sandpaper, relax tension, reduce pressure, and increase speed.
10 Uneven sanding
Cause: pre-treatment In addition to improper use, the main reasons are inconsistent tension and pressure on the left and right sides of the cloth, different sizes of gaps between the fabric and the abrasive belt, uneven sand grains on the abrasive belt, dampness of the abrasive belt, which reduces the sharpness of local abrasive grains, etc.
Solution: Strengthen pre-treatment to achieve uniform cooking: Adjust the left and right tension of the cloth and the pressure of the cloth pressing roller to make it uniform: Use a precision tape measure to correct the gap between the fabric and the abrasive belt ;Abrasive belts should be stored in a ventilated and dry place to avoid moisture.
11 Sanding gear
Cause: wrap angle is too small ;The cloth tension in and out is inappropriate.
Solution: Adjust the wrapping angle and the tension of the cloth in and out.
12 Grinding holes
Cause: convex on the cloth surface The yarn ends or yarn knots are raised, the gap between the cloth feeding end and the abrasive belt is too small, the cloth is wrinkled and curled when the cloth is fed, etc.
Solution: Choose a fabric that is flat and has few yarn ends or knots. Adjust the gap between the cloth feed roller and the gauze belt. The fabric feed should be smooth and without curling edges.
</o:p
