Defect Analysis And Solution Of Flat Screen Printing

Abstract: 31 common defects which are easy to appear in continuous flat screen printing are analyzed, including the causes of the defects, the phenomena of defects and various solutions.

The defects of flat screen printing are constantly changing. People have summed up it into several types. They can be distinguished when finished products are tested and named according to the phenomenon. In fact, the defects are rarely repeated, although the same phenomenon, but not necessarily the same reason. This article mainly analyzes the most common and vulnerable defects, analyzes the possibility of defects, and provides a way to analyze defects, for reference.

1 paste

The phenomenon is that the outline of the flower pattern is not clear, the color contact is blurred or the side road is pasting. According to the principle of pressure only paste, the wet press will be pressed into the previous version when wet printing is done, and the number of pressed plates will be more serious.

To overcome this situation, we must first select the appropriate scraper (hardness), scrape the printing and pick up the pulp to be clean; when there is a condition, draw the distance between the plate and the plate, and heat the air in the middle if necessary; arrange the position of the flower plate correctly, first print the stem and print the block surface; deal with the flower manuscript as little as possible when entering the road, avoid the excessive extrusion of the position, and make proper packing for the edge of the flower frame, so as to reduce the contact area of the stamping.

2 paste edges

Fabric edge pressing paste. Because of the uneven width of the gray cloth, narrow or wide, or the cloth is not on the same straight line, paste the two ends of the net screen to the guide band, then stick to the back of the next screen, then print to the next version of the selvedge, resulting in paste edges; the sucker is out of order, and the cloth edge is not in a straight line; the width of the flat screen after sealing is wider than that of the gray cloth door.

The solution is to rearrange the grey cloth with different width. The width of the machine must be uniform. The width of the screen ends and the edge of the printing position are not allowed to print the color paste onto the conduction band. The suction device is intact, and the distance from the guide strip is not drifting when the cloth is pasted. The width of the scraper is more than 5cm at each edge.

3 turn on

The flower shape is blurred, and the color of the pattern penetrated into the fiber direction.

The reason is: after the belt is cleaned, the water is not dried. After the fabric is affixed with a water guide, there is a watermark, resulting in the penetration of the pigment paste. The viscosity of the paste is low, the dye concentration is very strong, the printing volume is too high, or the amount of moisture absorbent is high, and the water holding capacity of the original paste is poor. All these will cause the printing to turn off.

Solution: check whether the water scraping device of the conduction belt washing box is good; choose the paste with good water holding capacity. Check the dosage of the process prescription is reasonable (the saturation of the dye, the amount of auxiliaries for different grey cloth), and the pulp should not be too long.

4 scraping in

The discoloured pulp is scraped in to form a wrong color or a dark color pattern.

The reason is: the dark flower block has many large strips of pulp; the edge of the flower frame is not good; the pulp is brought into the flower plate from the guide band. Add the wrong register when adding pulp.

Solution: block flower layout according to fabric door width. When printing, the pulp should be collected, added less and added to pulp. When changing the color, the blade should be cleaned to avoid the residual pulp coming into the new color matching pattern, and the pulp should not be added up. Change the position of the flower plate without affecting the color condition.

5 frame printing

The unusual pattern of flower plate frame appears on the pattern near the layout. This is due to improper screen printing. Poor frame installation, uneven height or gap between screen and conduction band is too small.

Solution: slightly raise the web frame or flat net frame, and also handle the correct opening of flower shape and keep the distance between flower pattern and net frame edge.

6 the color difference in the first edition (uneven scraping or showing a certain distance between the fabric and the shade).

The reason is that the screen is incongrittable, the thickness of the photoresist is uneven, and the uneven exposure of the flower shape affects the difference of the pulp volume. The two is that the frame is not on the same plane, or the installation is bad. Three, scraper loosening, scraper mouth uneven or scratch when printing.

Solution: for the defects caused by screen printing, we need to make a new screen. If the film is sensitive, we must check the quality of the film. Screen frame is pressed, but when printing, observe whether the flower is out of shape. Screen installation is high or low. The blade thickness is uniform, high and low, and the installation is in place.

7 offset printing

The printing plate is printed or overlapped or disconnected. The reason is that the setting of printing guide band is not allowed to be set up; the pressure on the scraper is not adjusted well: the net frame is too high from the conduction belt, and when the scraping is printed, the screen screen is removed. The size of the flower shaped open circuit is too large, resulting in the large area of the pressing area.

Solution: according to the pattern of flower position, the operation of the conduction band is reset, or the conduction of the conduction belt is normal; the scraper pressure is adjusted to the right time; the adjustment of the screen is high; the back of the screen can be partly covered by the big gap fine screen; and the unreasonable open road is modified.

8 Flower Edition

The color is uneven and has a chrysanthemum like fuzz. The reason is: when the flower plate is raised, the color paste is pulled up, and the color plate on the front side of the flower plate is stained with paste, which affects the printing of the first page. The viscosity of the paste is too thick or the expansion is insufficient; the dosage of certain dyes is too high.

Solution: adjust the viscosity of the pulp or adjust the puffing time of the paste; reuse the old pulp or replace it with new syrup; adjust the prescription and wash the flower in time.

9 flowers

The flower position is exposed to gray cloth or poor permeability, like the shape of the shark skin. The reason is: after making the flower plate, the curing agent is not: middle cleaning, or the use time of the flower plate is too long. The pulp makes the mesh smaller, resulting in a stopper; the blade is improper or too small, and the pulp is not enough; the viscosity of the paste is too thick to be scratched; there are oil stains and waxes on the gray cloth: the front set is not dry, and is sucked up by the reverse side of the rear set flower plate.

Solution: whether the check hole is good after the flower plate is produced; after each printing, the screen should be cleaned: select the scraper and apply it properly: the wool effect must be tested for the grey cloth to prepare the printing, and the rework of the grey fabric is necessary if necessary: each printing paste must be tested for the viscosity of the paste, and the mesh number corresponding to the flower pattern should be selected.

10 thick and thin stems

The causes of uneven thickness of thin stems are: coarse and thin defects in screen making; different sizes of magnetic materials on the magnetic stage, resulting in different printing pressure; uneven placement of web plates; uneven pressure on scrapers; uneven blade edges; inconsistent thickness of scraper blades; and scraping and printing.

Solution: check carefully whether each stem of the flower plate is the same stem; check the magnetic force of the magnetic stage; when printing the screen, it should be leveled: select the scraper and adjust the pressure on the train; when changing the blade, the knife must be consistent; adjust the height of the net according to the thickness of the fabric.

11 skew in flower shape

The pattern is inclined or curved to the warp and weft yarns of the fabric. Causes: printed fabric (silk) itself has oblique or slit head bad: stick skew.

Solution: printing grey cloth (especially printed geometric flower shape) needs full weft and inspection. After qualification, it can enter mass production: sewing seam is parallel to the weft parallel direction: sewing machine to keep cloth straight.

12 sand holes

The printed fabric is exposed to sand like size. The reason is: the use time of the screen is longer than that of the service life. The local photosensitive glue is off and permeated: the quality of the plate is not good, and the film is not firm. After the blade is scraped, the film falls off.

Solution: regular observation of screen, found that sand holes immediately repaired; check the screen before getting on the train.

13 leakage

Color appears in non flower shape. Cause: flower plate stripping or flower plate edge is not good.

Solution: screen before machine check, halfway to repair.

14 plug net

Incomplete or partial coloured spots, white spots or partial lack of flowers or sparse spots. Causes: there are impurities in the slurry, plug the mesh, especially pigment printing: after long printing, the edge of the mesh is blocked; the cloth is penetrated by impurities, and the case line is the first; when making the mesh, the sensitive film is not washed.

Solution: when the printing time was observed, it was found that the net was immediately wiped off the rubbish. It was found that the large area plug net immediately stopped to clean the screen; the filter color paste was obvious; the small block was obviously outside the garden net or the back of the screen had impurities and scraped with tools.

15 loose print (moire)

Ripples appear on printed patterns. The reason is that the mesh of the screen overlaps with the yarn organization of the printed fabric, resulting in interference; the web frame is too loose; the mesh number is not suitable.

Solution: the gauze should be stretched and the angle of the gauze should be maintained at 10 to 15 degrees from the fabric angle.

16 fuzz

The flower shape is fuzzy and has a shifted sense of ghosting. Causes: improper operation when starting the plate; the screen is stretched too loosely; the conduction belt operation is not synchronized with the screen operation; even the edition operation is pressed by the border frame.

The solution is to start or slow down the plate. The safety standard requires the framed frame to check the synchronization of the screen printing machine and the conduction band.

17 pulp printing

Like tadpoles. Causes: color paste is too thin, too much pulp, too fast pulp.

Solution: select the right raw pulp and adjust the required viscosity.

18 splash pulp

The splash of color splashes causes the dots or pulp to pull away. The reason is that the printing operation is too severe, and the color of the paste is not suitable; there is too much pulp in the pulp tank.

The solution is to adjust the viscosity of the lewd paste, operate the force properly, and do less effort.

19 flying points and color points

The colored spots of irregular dyes are sprinkled on cloth to form small spots of color. Or a monochromatic dot with the same color in the same color. The reason is that the printing paste is too sticky. After printing, the pulp is not clean. The printing plate is too fast and strong. In the colorant, there are undissolved dyes or impurities attached to the fabric.

Solution: raw pulp should be placed in sufficient time to make paste paste: improving printing printing operation, screen printing on single side, slurring, adjusting the speed of scraping and printing. For the dyestuffs that can not be dissolved, filter gauze with high number of gauze can be used.

20 crepe print

Printed cloth has white wrinkles. The reason is: the cloth is not pasted flat, and there are Zou prints. When printing, the color paste can not penetrate into the crease: the grey cloth is not firmly stuck, and it is taken up when the plate is printed, and the position of the printing is changed when the latter is pressed down again; the edge of the blank is wide and the edges are sharp, and creases are produced when the cloth is pasted.

The solution is to enter the cloth to be smooth, adjust the tension of the incoming cloth, check the resin stickiness on the surface of the conduction belt or the stickiness of the sticky paste, check the temperature of the hot roller or the pressure of the pressing roller, paste the paste or resurfacing the resin, and sew the head to be smooth without affecting the bonding effect.

21 exposure

A part of warp or weft yarn is turned or moved to the positive and negative sides of the fabric. Causes: color permeability is poor, dye can not penetrate into the fiber inside; scrape printing intensity is too small, the pulp is not enough, resulting in the actual color of the dye is not enough; the fabric is water repellent, does not absorb the color paste; after printing, after the washing process, the fabric is loosely woven, a small amount of fibrous dimension flip, exposing the bottom white.

The solution is to ensure that the swelling time of the original pulp is adjusted, and the mixing of the color paste is uniform. When printing, the color paste penetrates to 2/3 of the cloth thickness: the new fabric should be treated for the water repellent fabric; the tension should be uniform when printing, especially the twill and satin weave.

22 printing depth

The color of the same color or flower is deep and shallow, and the size of the mud is large. Causes: the resin on the conduction belt is uneven; the viscosity of the paste is too high, the moisture absorption of the fabric is poor, the blade force is uneven, the screen thickness is not consistent, and the screen is not at the same level.

Solution: check that the resin is smooth, like the surface of a mirror: check the viscosity of the color paste, adjust it; test the capillary effect of the grey cloth, and all the unqualified ones will be printed again after the repair. The blade is the same as the blade, and the blade pressure is the same as that of the scraper.

23 left, right, middle and deep

The two sides of the cloth are different from the hue and depth of the middle. Causes: poor scouring and bleaching of fabric; bad installation of screen frame; insufficient stroke of scraper: too thick resin for printing guide band.

Solution: when the fabric is drifting, the cloth will be evenly distributed to pH; the net frame will be at the same distance from the guide band; the scraper scraping distance exceeds the 5cm of the cloth edge to prevent the deceleration effect when the scraper turns; printing the cloth with different gate width, changing the placement position.

24 water stains

Stains or blotch caused by water droplets. Causes: water scraping is not clean or dripping in the dripping room; after printing, the semi-finished products are not properly protected for a period of time before the end of the steaming process, and the water dripping on the top of the steaming machine is caused by condensation water or splashing water drops.

Solution: check the smoothness of the water scraping knife of the water tank of the conduction belt, repair in time, protect the semi-finished products, use cloth bags: stop the steaming, check the causes of the dripping water of the steaming machine, and solve the problem after being steamed.

25 holes

The fabric is strongly damaged at the printing place, and the warp or weft is broken. The reason is that the content of reducing agent (engraving degree) in the printing and printing paste is higher than that in the printing paste.

Solution: adjust the carving degree, just to engrave the net and hair color; arrange printing and steam wash after printing.

26 relief

In the anti printing (coating prevention) and carving, the color around the flower is irregular. The reason is: the amount of reducing agent is too high, the whole process is not decomposed during the steaming process, and the color is continually damaged under the condition of damp heat. When printing, the screen is stained behind and the flowers are not allowed; when the net is stretched, the tension of the gauze is too loose.

Solution: according to the amount of dyestuff and the depth of printing, control the amount of reducing agent correctly, use the forward line test, pay attention to the operation of printing, do not frequent debugging; screen tension is uniform and suitable.

27 the color is not clean or the effect of dyeing is bad.

The reasons are: the amount of reducing agent is not enough or the amount of auxiliaries is not good: the amount of pulp is too little during the printing process; the exposure time in the air after printing is too long, the oxidation is earlier, the conditions of steaming are not appropriate, and the pullability of the ground dye is poor.

Solution: before printing, it is necessary to carry out the white test on each vehicle's color cloth to prevent uncloths from entering the printing process. Before printing, the effective components of the reducing agent in the colorant are measured before printing; the scraping and printing are suitable for the pulp, and enough pulp is maintained on the cloth surface; after printing and drying, the fabric is wrapped with cloth, so as to prevent oxygen from being encountered in the air and to oxidize earlier, and to steer in time, and to maintain steam pressure when steaming.

28 friction stains pull away

Fuzz in one direction at the edge of flower pattern. Causes: printing drying, the drying room temperature is low, not timely drying, when the cloth on the move friction and drag; when printing prints not fully dry when exposed to foreign bodies, and stained to other parts of the defects; in the printing fabric drying insufficient condition of the fabric towed.

Solution: after printing, the drying room should be leveled, the drying temperature is guaranteed, the drying temperature is determined, and the drying temperature is determined according to the thickness and speed of the fabric.

29 when printing, the fabric is locally raised, and the printing part is expanded and separated from the conduction band, similar to the form of the velvet yarn, such as the thin polyester fabric printing, nylon umbrella silk printing.

Cause: fabric is wet and elongated.

Solution: before printing, the styling fabric is stretched until it loses its elongation space after being wet.

30 print flower shaped arch

The fabric is uneven, showing the stretch printing part of elastic fabric or knitted fabric. The reason is that elastic fabric or knitted fabric has certain elasticity. When the cloth is stretched, the fabric of the printed part is fixed in the condition that the fabric is stretched. It is restored to the original state for the printing part. As the printing and non printing parts shrink, the cloth is raised.

Solution: before printing, the fabric is over fed and even exceeds the shrinkage of the finished product.

31 after finishing, the color fastness decreased, and the color fastness index after washing was up to the standard. However, after softening or some finishing, the color fastness (especially rubbing fastness) of the finished product decreased by half or even one level.

Causes: a softener is added to form a film on the surface of the fabric, which is bonded with the fiber and is also bonded with a part of the dye. Therefore, the dye is carried out when it is rubbed. In particular, the combination of disperse dyes and fibers is the coupling of electron molecules and electron withdrawing molecules on dye molecules to make the dye molecules even polarized, forming a dipole moment with the =C=O group on the fiber and forming a hydrogen bond. At high temperature, a small amount of unbound or unbound disperse dyes are easily precipitated.

Solution: choose suitable softeners for reactive dyestuff printing. For disperse dyes printing, the most convenient solution is to enter the fresh water simply after a high temperature baking.