Offset printing technology experience - paper adhesive rubber failure processing

Solve the problem of sticky eraser for small offset press

In the offset printing process, the paper sticky rubber refers to the phenomenon that it is common for the surface fiber material of the paper to be adhered to the surface of the blanket during the printing process. Paper viscous erasers generally appear when the full-print version is used on the spot or when the ink is used in a large amount. Especially when printing coated paper, when the printed ink is thick and the ink volume is large, the paper is erased. The phenomenon is prone to happen. It affects the reproduction of graphic products of printed products and the integrity of outlets so that printing cannot be carried out. Ink is printed on paper to cause waste. If it is not found that the blanket will be indented or the printing cylinder will transfer the paper adhered to the surface of the blanket to the ink roller, so that the print adheres to the paper residue and the printing is interrupted. The improper adjustment of the paper-feeding mechanism of the offset printing press is one of the causes of paper stickiness and eraser. There are other aspects as well.

1. The biting force of the embossing cylinder biting paper teeth is not enough

Offset printing, especially in the printing of high-grade coated paper, textured paper, offset paper, etc., encountered a large area in the field, with a large amount of ink, the ink layer required full and thick, paper sticky rubber is prone to occur, mainly due to the imprinting cylinder bite paper Insufficient biting force.

Solution: The nip bite force of the impression cylinder is not enough, it will cause the problem of inaccurate printing overprinting, increase the biting force of the impression roller to bite the paper teeth, and can bite the force of biting the paper teeth, so that the bite of the bite paper teeth Uniform force. If the overall teething force is still insufficient, the strength of both sides of the brace spring can be increased; if the bite piece or pressure pad is too smooth to cause the paper to stick to the rubber, it can be solved by sticking fine gauze on the tooth pad to make the bite paper pad rougher Only bite the paper to prevent the bite force of the bite paper teeth from being insufficient, causing the paper to stick to the rubber.

2. The transfer time between the roller's bite teeth and the delivery teeth is not correct

During the offset printing process, the paper is bitten from the swinging paper feed teeth, to the roller bite paper teeth to complete the printing process, and then delivered to the delivery teeth, there must be a certain transfer time between them to ensure the accuracy of overprinting and paper transfer process Continuity, if the transfer time between the roller bite and the delivery bite is too short and the transfer time is too early, too late or incorrect, it will lose control of the paper in an instant and cause the paper to stick to the eraser.

Remedy: Adjust the position of the opener at the junction of the delivery paper catcher and the roller holder, so as to prevent the user from tearing the paper, control the delivery time of the two in the range of 3 to 6 mm.

3, receive paper teeth bite too light

When the delivery bite bites into the paper, the back end of the paper does not come off the roller. At this time, the paper will still be in a rolling state. If the bite force of the delivery bite is small, it is impossible to bite and bite the paper. The back of the paper is easily adhered to the surface of the blanket. This also causes the paper to stick to the blanket.

Solution: The bite force of the delivery teeth is determined by the spring force of the four springs on the axis of the delivery teeth. If the bite force of the overall delivery bite is too light, the four springs can be pressed at the same time to increase the bite. Force, and then adjust the bite force of each bite, with 60g/m2 kraft paper into the teeth, pull the test out, so that the teeth on the middle and both ends of the bite force uniform, if the bite paper or tooth pad is too smooth cause the paper to stick the rubber , Can be stuck on the toothpaste sticky gauze or tape paste on the bite pad to eliminate the malfunction.

4, excessive pressure between the blanket cylinder and the impression cylinder

In the offset printing process, if the printing pressure is too high, it will cause the paper to stick to the blanket. Even if the bite force of the roller bite and the delivery teeth is increased during the failure, this phenomenon occurs frequently, especially in the printing ink layer. Thicker, more glossy coated paper is more common on paper. At this time, the frictional force generated due to excessive printing pressure is greater than the bite force of the bite. This causes the paper to stick to the blanket and make the paper on the blanket. The surface layer is very tightly adhered and it is very laborious to tear off the paper by hand. This explains why.

Solution: The entire offset printing process is to solve the contradictory process between ink and paper. To transfer a certain thickness of ink graphic on the printing plate to the printed paper, it must be transferred during the graphic transfer process. Apply a certain amount of pressure. People often say that "without pressure, it is not a matter of printing", which fully explains the importance of printing pressure.

Since printing pressure is so important, is it better that the pressure is greater? Of course not. In general, the appropriateness of printing pressure is often manifested by the print quality of printed products. Printing pressure should be based on the premise that prints have strong dots, clear graphics, bright colors, and light shades, and the smaller the application, the better.

In order to avoid the printing pressure is too large, resulting in paper sticky rubber, so that clear and complete printing dots, should use the minimum pressure, use neutral and soft lining material.

5, delivery paper bite shaft positioning is incorrect

Under normal circumstances, the position of the delivery nipper axis before the offset printing machine is basically correct. However, in the processing of the delivery nib shaft cover, it is inevitable that there will be some errors. During the adjustment of the delivery clenching process, each row of delivery teeth and the dental pad can not maintain the consistency of the position, in the transfer of paper with the impression cylinder teeth, reflecting the distance between the delivery teeth and the impression roller front mouth is not consistent, if Some distances are too large, which will cause the receiving paper bite to bite the paper or bite the paper too little, causing the paper to stick to the eraser.

Remedy: For incorrectly positioned take-up teeth row, relocate by replacing the new shaft cap to solve. For improperly adjusted delivery teeth and teeth pads, re-adjust them so that each tooth pad is in the same parallel. on-line.

6, the viscosity of the ink caused by the paper sticky rubber

Offset overprinting y, m, c, Bk four-color commonly used ink, its viscosity is Bk> c> m> y, black ink viscosity, yellow ink viscosity is the smallest, so offset printing darker ink, due to viscosity , prone to paper glue eraser failure.

Solution: 1 In order to make the ink has a good printability, in the transfer of ink often according to the requirements of the printing, appropriate to add some auxiliary materials to adjust the viscosity of the ink. Can be added 6 # varnish, 6 # varnish is a dry vegetable oil obtained by heating and refining a yellow oil viscosity of a certain fluid material, 6 # varnish can play two roles : a, that is to play a dilution role in the ink; b, play a role in reducing the viscosity of the ink, when the 6 # varnish is added to the ink, reducing the viscosity, concentration of the ink, increasing the flow of the ink, show Brushing enhances the printability of the ink.

2 Add a detackifier to the ink. The detackifier is a mixture of wax pastes and is an auxiliary material for adjusting the viscosity of the ink. Without increasing the fluidity of the ink, the viscosity of the ink can be reduced and the length of the ink can be shortened.

In summary, the failure of the paper glue eraser is caused by many factors. The problem of paper sticking and erasing in the work requires comprehensive analysis and differential treatment. In addition to failures in the delivery, receipt, and delivery of paper in the offset printing press, poor printability of raw paper and ink is one of the reasons.