Briefly discuss the printing in the common quality problems and their solutions

In the process of printing, with the transfer of ink, often will happen a lot of problems, directly or indirectly affect the printing quality.For example, ink dieyin problems can lead to hair flower pictures;Ink penetration will cause the overall smearing, telegraphing;May occur at any time in the process of printing misting, ghosting phenomenon will affect the quality of the newspaper.

Hair flower pictures

Pictures hair flower phenomenon often appears in printing process, the main reason is ink dieyin problems.And images, colour reduction effect are also associated with ink dieyin successively and dieyin rate.

Also called ink dieyin rate of ink, is to measure the degree of ink dieyin quantity, the higher the value, dieyin the better the results.Determination of the density of a monochrome ink, by using the subtractive install a filter in the densimeter, the color of color filter and normally measured the color of the ink into a complementary color.

Dieyin way with dry dieyin and wet overprint.Dry color ink before dieyin refers to the basic color ink dieyin again after drying.Wet overprint refers to the color ink without completely dry before the second color ink dieyin.A very short interval between each color newspaper printing, ink film is attached to each other in the wet state, belong to the wet overprint.Increase the rate of wet overprint of ink dieyin the need to control the ink adhesion and viscosity, general requirements set of of all kinds of printing ink viscosity in order for the first color > > the second color 3 color > 4 color, should also consider the ink film thickness and printing color sequence.Newspaper printing base with black gives priority to tone, so should use green - magenta - yellow - black printing order.

Smearing, telegraphing

Handwriting is not clear, often appears in print advertising fuzzy situation, the causes of this situation on the one hand is a paper roll and triangle JiMo too much, on the other hand may be ink penetration.The former only clean paper roll and triangle, the latter is more complicated.

Printed with newsprint paper surface smoothness is poorer, when newsprint entering stamping area, ink under the effect of pressure is dependent on the size and distribution of paper's capillary is, pressure infiltration and free penetration at the same time.In the process, if the improper control could appear zi mo or telegraphing phenomenon, resulting in a printing quality.Experimental data proved that the penetration depth is proportional to the time stamping, is inversely proportional to the ink viscosity, and increases with the increase of printing pressure.

In addition to water less as far as possible keep the ink balance, control education version of liquid dosage, reduce the ink emulsification phenomenon, is advantageous to the ink dry;To the related parameters were determined, the choice is suitable for paper, speed up the ink fixation in the printing process, to solve the smearing, telegraphing is also very important.

misting

In the printing process, due to the high speed operation, it is easy to produce fly ink phenomenon, not only pollute the environment, also cause serious damage to workers' health.The factors influencing misting generally can be divided into mechanical factors, environmental factors, printing ink.

1. Mechanical factors

Printing speed faster, the ink silk fracture more generally, the more serious the electric double layer destruction.Actual printing process, to reduce misting phenomenon, to control the printing speed, usually the small cylinder press printing speed control about 600 r/min, can also use the same principle, in contact with certain parts of the inking roller mounted on low voltage wires.

In addition, the more ink layer thick, divides in wire drawing, breaking the more ink, the more serious the misting.

2. Environmental factors

Under the same temperature, humidity, the greater the ink silk fragment with the less charge, misting phenomenon the lighter.In the actual printing process, increase the humidity workshop, improve ventilation, timely supplement of fresh air, to reduce the misting has certain effect.

3. The ink factors

Mitosis, the greater the ink particles of the ink the more fragment, misting phenomenon is more obvious.In the actual process of printing, using the smaller the particle size, or adding proper plasticizer of ink, to reduce the misting have certain effect.

ghosting

In rotary printing press in the process of high-speed operation, as long as the tiny displacement between rollers, rubber cloth last transfer the remaining ink cannot with the next transfer of the ink layer completely overlap, will produce double fault.Ghosting into vertical ghosting, transverse ghosting, AB ghosting.Double fault in a newspaper printing most belong to the longitudinal double.

1. The longitudinal ghosting

Vertical double top and bottom side of the network virtual shadow in the branch, and the drum shaft to the vertical.The cause of the problem have the following points.

(1) the roller shaft and shaft sleeve, eccentric sleeve clearance is too large, lead to drum vibration during high speed running.Fitting clearance of roller shaft and shaft sleeve should be controlled between 0.01 ~ 0.02 mm, more than 0.05 mm need to repair.

(2) the drum gear wear serious, gear mating and backlash increase, making the displacement between roller.

(3) the improper packing, the pressure is too large, the surface of the linear velocity, resulting in excessive extrusion, extrusion value changed rubber cloth, make rubber cloth can't bounce back to the front of the compression state.

2. The horizontal double

Horizontal double network virtual shadow in the left and right side of the original branch, and drum axial parallel.If appear this kind of circumstance, may be roller thrust bearing screw loosening or wear and tear, rubber roller axial displacement happened in high speed.

3. AB ghosting

AB ghosting network virtual shadow position is not fixed, sometimes in the upper and lower side, sometimes in the left and right side.Are not likely to appear this kind of circumstance, usually in the printing process if there may be both failure occurred at the same time, the design and manufacture of precision or the machine itself is not enough.