Technology | Common quality problems and preventive measures in sanding finishing

Grinding is a meticulous work. If you are not careful, you will not accept it from the customer, and you will lose the cloth. So what should be paid attention to in the finishing?

01 Crumpled print

If the sanded products are improperly processed, regular or irregular warp and weft creasing marks can be produced on the fabric surface, which will seriously affect the appearance quality and sanding effect of the product.

The main reasons for wrinkle printing and the measures taken are as follows:

1. The fabric is stacked in a folded (or wrinkled) state for a long time, and it is pressed by its own gravity, resulting in irregular warp and weft creasing prints on the surface of the fabric. For this reason, the storage method of fabrics should be changed to large coil storage (stacked) coil storage, which can effectively prevent creasing and printing.

2. In the pre-processing of sanding, the falling temperature of the fabric is too high, causing relatively permanent wrinkles. This is mainly for chemical fibers and their blended fabrics. This type of wrinkle is difficult to remove and often requires one-time styling. For cotton-type or lightly crumpled fabrics, spray wet and drying equipment can be configured before the sanding machine to solve the problem.

3. In the fabric pre-treatment and dyeing process, due to process, equipment and operation problems, or improper seam heads, wrinkle streaks can be caused. Therefore, in order to overcome the embossing and printing defects of sanded products, all procedures should be strictly checked.

Usually in the process of sanding, the original weft crimping of the fabric can be removed, but the warp crimping can not be removed, leaving the surface of the fabric with traces of uneven fluff and different shades.

02 white core

The white core produced by the surface of the woolen fabric is mainly due to the fact that there are neps on the grey fabric. These neps can be covered after dyeing, but once the wool is sanded, the neps are worn away and white spots are left, which may even cause small breakages. Hole, affecting product quality. Therefore, for the original grey fabric, it is required to reduce the neps as much as possible, or pick the neps to the opposite side of the fabric; the process of sanding before dyeing and dyeing after sanding can also be used to prevent white core defects.

03 strip flower

Causes: 1. The surface of the sanding roller is uneven or the sand skin is improperly covered, resulting in uneven abrasive grains and streaks. 2. The sanding roller is used to grind narrow fabrics first, and then to grind wide fabrics. Because the surface of the sanding roller is not uniformly worn, it is easy to cause the unevenness of the grinding edge and produce streaks on both sides.

Solution:

1. The emery skin should be flat and tightly pressed against the guide roller, the guide should be straight, the surface should be flat, and it should be kept clean and no dirt left.

2. The emery skin should be slanted or strip-shaped, and the two ends should be rolled firmly.

3. Check the equipment regularly to ensure that the guide roller is flat and the sand skin and the guide roller are in good bonding state.

04 chromatic aberration

After the fabric is sanded, the color and luster will have some changes. Generally it becomes lighter, resulting in a certain color difference between sanding and unsanding. This is mainly due to the different reflection of light by the fluff on the surface of the sanding fabric. Therefore, the color difference after sanding should be fully considered when dyeing, and there should be a slight margin for the depth of dyeing. In addition, the penetration rate is the key, and the requirements for penetration are higher than that of ordinary dyed fabrics.

Experiments show that different types of dyes have different effects on the chromatic aberration of fabrics before and after sanding due to their molecular structure, dyeing performance, and affinity. For example, light-colored fabrics with vat dyes and reactive dyes have a small color difference before and after sanding, which is suitable for the process of dyeing and then grinding; for medium and dark fabrics, the color difference before and after sanding is large, which is suitable for the process of sanding and dyeing. It can also achieve the best effect of velvety and fullness and even dyeing.

05 Fold

Causes: semi-finished product wrinkles, mercerized clips, crescent folds; pressure folds that occur after a long stacking time; non-parallel cloth guide rollers cause live fold prints and folds caused by the edge suction device, and the drying cylinder is not flat, causing the drying cylinder to flex.

Solution: Mercerizing machine repairs semi-finished crescent folds and clevis folds, drying cylinder edge suction folds, etc., which can be repaired on the stenter machine.

06 Poor sanding effect

Causes: The semi-finished product feels hard, the cloth surface has poor penetration effect, the tension is small, the speed is fast, the sand skin has been used for too long, the speed of the DC motor is unstable and the cloth is damp.

Solution: notify the pre-treatment to repair or apply softener, tighten the tension of the chain shaft, reduce the speed, increase the pressure, replace with new sandpaper and fully dry the cloth surface.

07 Grind Willow

Causes: overlapped seams of sandpaper, the direction of rotation of sandpaper is the same, thread ends are wound on the grinding roller, and the joints of sandpaper are printed or damaged.

Solution: Re-tighten the sandpaper, change the direction of rotation of the sandpaper, and adjust left and right to clean the thread ends on the grinding roller.

08 Left center right gross difference

Causes: the left and right press rollers are unbalanced, the sandpaper has been used for a long time, and the degree of abrasive wear on the edges is different.

Solution: Adjust the balance roller to make the left and right balances consistent, and replace the new sand skin to solve the problem of the difference between the two sides of the narrow width.

09 Poor strength

Causes: the fabric yarn is thin, the sandpaper mesh is low, the strength is large, the pressure is large, and the speed is slow.

Solution: Replace high-mesh sandpaper, relax tension, reduce pressure, and increase speed.

10 Uneven sanding

Causes: In addition to improper pretreatment, the main causes are the inconsistency of tension and pressure on the left and right of the cloth feed, the difference in the size of the left and right gaps between the fabric and the abrasive belt, the uneven sand on the abrasive belt, and the dampness of the abrasive belt reduces the sharpness of local abrasive grains.

Solution: Strengthen the pre-treatment to achieve even cooking; adjust the left and right tension of the cloth and the pressure of the cloth roller to make it uniform; use a precision tape measure to correct the gap between the fabric and the abrasive belt; store the abrasive belt in a ventilated and dry place to avoid moisture .

11 sanding files

Cause: the wrap 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 Frayed Hole

Causes: there are raised yarn ends or knots on the cloth surface, the gap between the cloth drop and the abrasive belt is too small, and the cloth is wrinkled and curled when the cloth is fed.

Solution: Choose a fabric that is flat and has few yarn ends or knots, adjust the gap between the cloth feed roller and the yarn belt, and the cloth feed should be smooth without curling.