Sanding finishing uses sharp abrasives (emery rollers or metal rollers) to grind the surface of the fabric. During operation, the high-speed sanding roller is in close contact with the fabric. The abrasive sand particles first draw out the fibers in the fabric yarn. , and cut into single fibers with a length of 1 to 2 mm, and then rely on further high-speed grinding of the abrasive to form a uniform and fine suede surface on the fabric.
Sanding is a delicate work. If you are not careful, it may cause the customer not to accept it, or it may cause the fabric to be damaged. So what issues should be paid attention to during the sanding and finishing?
01 Wrinkle mark
If sanded products are not processed properly, they may appear on the surface of the fabric. Regular or irregular warp and weft wrinkle marks are produced, which seriously affects the appearance quality and sanding effect of the product. The main causes of wrinkle marks and the measures taken are:
(1) The fabric is stacked in a folded (or wrinkled) state for a long time, and is pressed by its own gravity, resulting in uneven wrinkles on the surface of the fabric. Regular uneven warp and weft wrinkles. For this reason, the storage method of fabrics should be changed to rolling (folding) rolls in large rolls, which can effectively prevent wrinkle marks.
(2) During the pre-sanding process, the drop temperature of the fabric is too high, resulting in relatively permanent wrinkles. This is mainly for chemical fiber and its blended fabrics. This type of creasing is difficult to remove and often requires a styling session. For cotton type or lightly wrinkled fabrics, spray moistening and drying equipment can be installed in front of the sanding machine to solve the problem.
(3) In the fabric pre-treatment and dyeing process, wrinkle marks can be caused due to process, equipment and operation problems, or due to improper seam ends. Therefore, in order to overcome the wrinkle and print defects of sanded products, each process should be strictly controlled.
Usually during the sanding process, the original weft wrinkle marks on the fabric can be removed, but the warp wrinkle marks cannot be removed, leaving traces of uneven pile and different shades on the surface of the fabric.
02 White core
The white core produced by sanded fabric surface is mainly due to gray fabric There are neps left on the fabric. These neps can be covered after dyeing, but once they are sanded, the neps are worn away and white spots are left. In severe cases, small holes may even be caused, affecting product quality. Therefore, for raw gray fabrics, it is required to reduce neps as much as possible, or to move neps to the reverse side of the fabric; the process of sanding before dyeing and dyeing after grinding can also be used to avoid white core defects.
03 Stripes
Causes
(1) The surface of the sanding roller is uneven or the abrasive coating is improper. The abrasive grains are uneven and streaks are produced.
(2) The sanding roller is first used to grind narrow-width fabrics, and then to grind wide-width fabrics. Due to the uneven surface wear of the sanding roller, it is easy to cause uneven grinding and stripes on both sides.
Solution
(1) The emery leather should be flat and tightly rolled with the guide roller. The guide roller should be straight and the surface should be flat. It should be kept clean and no dirt should be left.
(2) The emery leather should be rolled in an oblique or strip shape, and both ends should be rolled firmly.
(3) Regularly inspect the equipment to ensure that the guide roller is flat and the bonding between the sand skin and the guide roller is in good condition.
04 Color Difference
After the fabric is sanded, the color will change. Generally, it becomes lighter, resulting in a certain color difference between sanded and unsanded. This is mainly due to the different reflection of light by the fluff on the surface of the sanded fabric. Therefore, when dyeing, the color difference after sanding should be fully considered, and a slight allowance should be made for the dyeing depth. In addition, the dye-through rate is the key, and the requirements for dye-through are higher than those of ordinary dyed fabrics.
Experiments show that different types of dyes have different effects on the color difference of fabrics before and after sanding due to their different molecular structures, dyeing properties, and affinity. For example: light-colored fabrics with vat dyes and reactive dyes have a small color difference before and after sanding, so they are suitable for dyeing first and then grinding process; medium and dark fabrics have a large color difference before and after sanding, so they are suitable for the first grinding and then dyeing process. It can also achieve the best results of plump and even dyeing.
05 folds
Causes
Semi-finished products are wrinkled, mercerized and crescent folded; crescents caused by long stacking time ; The non-parallel cloth guide rollers cause loose folds and folds caused by the edge suction device, and the unevenness of the drying cylinder causes loose folds of the drying cylinder.
Solution
The mercerizing machine repairs the crescent folds and dropped clip 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 It feels 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 too long, the DC motor speed is unstable and the cloth is damp.
Solution
Notify the pre-processor to 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
The seams of sandpaper overlap and the sandpaperThe moving direction is consistent, 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 threads on the grinding roller.
08 Left, middle and right hair difference
Cause
The left and right cloth pressing rollers are unbalanced, and the sandpaper has been used for a long time. Grit wear varies.
Solution
Adjust the balance roller to make the left and right balance consistent, and replace with new sand leather, which can 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 mesh is low, and the strength is poor Big, stressful, slow.
Solution
Replace high-grit sandpaper, relax tension, reduce pressure, and increase speed.
10 Uneven sanding
Causes
In addition to improper pre-processing, the main reason is that the tension and pressure on the left and right sides of the cloth are inconsistent , the size of the left and right gaps between the fabric and the abrasive belt is different, the sand grains on the abrasive belt are uneven, and the moisture in the abrasive belt reduces the sharpness of local abrasive grains, etc.
Solution
Strengthen pre-treatment to achieve even 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
The wrapping angle is too small; the tension of the cloth in and out is inappropriate.
Solution
Adjust the wrapping angle and the tension of the cloth in and out.
12 Grinding holes
Causes
There are raised yarn ends or yarn knots on the cloth surface, and the fabric ends and The gap between the sanding belts is too small, causing the cloth to wrinkle and curl when feeding.
Solution
Choose fabrics that are flat and have 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. </p
