Treatment of common problems in the most popular s

Treatment of common problems in sheet coating (II)

3. Scratched

taps ② the belt driving the force measuring piston to rotate has broken; During the production process of iron surface coating, due to mechanical reasons or defects of the tinplate itself, we suggest that only one condition film surface scar can be adjusted at a time when adjusting the mold test conditions. The scratch of the inner coating of the food can will greatly reduce the corrosion resistance of the inner coating

1) conveyor. Through the coordinated action of the iron suction nozzle and the iron supply nozzle, the sheet is sent to the less cloth machine. If the separation between the sheet to be separated and the next sheet is not complete, and the cutting edge of the trailing edge of the sheet is downward, it is easy to cause the blade of the last sheet to hurt the less film on the surface of the next sheet when the air nozzle is feeding; The unsmooth surface of the conveying trough for transporting tinplate will also cause scratches on the film on the back of the tinplate

treatment method: when the next surface of the sheet is scratched, adjust the action of the iron suction nozzle and the iron supply nozzle to make them cooperate tacitly, and adjust the position of the surrounding magnets and the direction, position and air volume of the air blowing nozzle at the same time, so that there is a gap between the upper and lower sheets when they are separated; In addition, turn over the sheet and apply white magnetic oil, so that the cutting edge of the trailing edge of the sheet is upward, which can also prevent the cutting edge of the trailing edge of the sheet from scratching the printing ink layer during printing. Of course, when the cutting edge of the trailing edge of the sheet is upward, it will damage the printing blanket during printing; When marking the back of the sheet, check whether the surface of the conveying trough is smooth. If possible, install several groups of rollers beside the conveying guide rail to let the sheet roll through during conveying

2) flower iron frame device. The surface of the patterned iron frame is not smooth, and the driving of the patterned iron frame is unstable when transporting tinplate, with intermittent vibration, which is very easy to cause Scratch on the film on the back of the tinplate in the drying room; When the tinplate enters the drying room after coating, it is not synchronized with the rotation of the patterned iron frame, which is also very easy to cause less film scratch on the back of the tinplate. The faster the coating speed is, the more serious the scratch is

treatment method: replace the unsmooth flower iron frame in time; Regularly check whether the supporting rollers driving the flower iron frame are worn; Adjust the time when the sheet enters the drying room, so that the sheet enters the drying room and is just found by the flower iron frame, so as to avoid friction and scratches on the flower iron frame when the sheet enters the drying room

3) the function of the receiving and loading structure 1 is integrated, and the trend of intelligent functional materials is obvious. When the wind volume of the receiving air is insufficient, the accumulated sheet is very easy to cause friction between the next sheet and the previous sheet, so as to scratch the back of the previous sheet. This kind of scratching is particularly obvious when the cutting edge at the trailing tip of the sheet is upward. In addition, the unsmooth surface of the receiving chute is also an important factor causing scratches

treatment method: the scratches caused by the unsmooth surface of the receiving groove are generally fixed at a certain position, and this position is generally supported by the seemingly smooth supporting iron, and the burr can be found on its surface and polished; Friction scratches caused by insufficient air volume are generally irregular, which can be solved by adjusting the blowing volume. The amount of blowing depends on the weight of the sheet

4) baking temperature. When baking the film, the temperature is low, which is often easy to cause poor film polymerization conjunctiva on the surface of the sheet. The polymerization force between the resin polymers in the film is poor, which is easy to cause scratches in production. Too high baking temperature is also easy to cause less film embrittlement, and it is easy to scratch after mechanical processing in the next process

treatment method: strictly control the less cloth temperature and coal baking time to make the film polymerize firmly. And regularly check the temperature in the drying room, and control the error between the relevant temperature value in the drying room and the temperature value of the drying room temperature display instrument within ± 3 ℃

5) carry the sheet by hand. In the process of printing or coating, in order to check the coating or printing effect of tinplate, the relevant quality is often sampled and checked. If you don't pay attention, it is easy for the new factory to have three 100000 level clean rooms producing medical grade pipelines and accessories to cause sampling scratches. In addition, when there are quality problems in printing or coating, you need to move the tinplate when picking out waste or defective products, causing scratches

handling method: handle the sheet gently when handling it manually; If there are quality problems such as printing pictures and texts, it is best not to move and pick up the tinplate before canning, especially those tinplate products with internal coating. If the tinplate is moved in pieces to pick out several defective products, it is easy to cause scratches on the internal and external surfaces of the whole product, and in serious cases, the food cans are prone to corrosion and even perforation

4. bar stripe fault

1) gear wear. The gears of the coater cannot rotate smoothly due to wear and poor meshing, resulting in uneven coating and bar shaped spots

treatment method: replace the gear

2) there is hard dirt between gears. There is hard dirt between the gears, which causes the jumping between the roller and the roller during coating, forming bar stripes

treatment method: clean the gear

5. sticking

sticking refers to the phenomenon that sheets stick together when the baking temperature is insufficient or the rice outlet is not cooled sufficiently, and the sheet is stacked at high temperature. If you peel it off one by one, it will make a sound, sometimes accompanied by dirt on the back of the sheet. With a long accumulation time, the dirt on the back is particularly serious. In addition, when the coating thickness is too thick, the organic solvent in the coating close to the tin layer volatilizes incompletely, which cannot be firmly adsorbed with the tin layer, and it is also very easy to stick when stacking

treatment method: bake at high temperature within the ideal baking temperature range of the coating, so that the coating can fully polymerize the conjunctiva on the surface of the sheet. If the problem cannot be solved by increasing the temperature, the problem can be solved by reducing the coating speed, extending the cooling time after the tinplate is discharged or adding the cooling air volume (changing to high-power fan). If there is sticking on the coated sheet, the sticking phenomenon can be eliminated by baking it at a high temperature within the ideal baking temperature range of the coating. When it is necessary to coat a very thick film, in order to prevent sticking, two coats should be used to improve the adhesion between the film and the sheet. (to be continued)