Analysis Of Folding Fault Of Commercial Cylinder For Rotary Printing

The commercial cylinder for rotary printing has the advantages of fast printing speed, many printing pages, and stable quality. However, the problems in production are also very complex. When there are problems, if we can not take corresponding measures in time and quickly, it will cause great economic losses. Among them, the accuracy of folding, as the last process of commercial rotary printing, is directly related to the smooth progress of the next process, and has a fatal impact on the quality of finished products, causing rework, increasing costs, and batch scrapping, resulting in serious quality accidents. In this paper, the author will analyze the common folding faults, hoping to help peers.

Folding process

The folding process is generally divided into the following steps:

(1) after the printed paper is vertically folded by the triangle plate, it is caught by the pick-up needle on the folding roller when passing through the guide roller and the paper clamping roller; 

(2) when the paper passes between the rubber pad of the cutting knife and the cutting knife roller, the serrated cutter cuts it into single sheets; 

(3) the planetary folding knife on the folding roller turns the single sheets horizontally; 

(4) after the transverse folding, the paper is handed to the grabber by the biting knife The paper thread is taken to the folding knife to finish the last folding; 

(5) the folded Book thread falls into the wing wheel and then is sent to the conveyor belt.

Common fold faults and measures

(1) skew, mainly divided into regular skew and irregular skew.

For regular skew, if the three folds are not on the same fold line, one side is on the fold line, and the other side is on the left or right side of the fold line, the following measures shall be taken:

① adjust the pressure of the elastic gasket on both sides of the folding knife to ensure that the force on both sides of the book post is balanced before folding;

② adjust the pressure of the brush on both sides of the folding knife to check the wear of the brush, and replace it if necessary;

③ check the bite knife and bite knife Wear of back and stopper. If the hinge skew is caused by wear, it must be replaced in time. When replacing a new folding knife, ensure that the highest point between the folding knife and the undercut is ≤ 3.5mm and ≥ 2.5mm. In addition, it is also necessary to ensure that each folding knife is consistent. When the folding knife and the undercut are handed over, there is a gap of 1mm between the folding knife and the undercut back. When replacing the new undercut and the undercut back, the biting force between the two will be tight. At this time, it is necessary to adjust the biting force between the two properly, so as to make the service life of the undercut and the undercut back longer.

For irregular skew: 

① check whether the wire belt is damaged, replace it if necessary, and when welding the wire belt, the interface must follow the direction of the book post, in addition, check whether the tension of the upper and lower two wire belts is consistent; 

② check the concentration of silicone oil when printing light coated paper and copperplate paper, the concentration of silicone oil shall be controlled to a small point (generally 10:1), and low quantitative cold fixed paper or overpressure paper shall be printed The concentration of silicone oil should be properly controlled.

(2) after the newspaper version of the book post rack knife, the inside and outside two fold a good and a bad phenomenon.

The measures to be taken are: adjust the pressure of the paper clamping roller and the direction of the paper guiding roller.

(3) the phenomenon of "eight character crease" appears after folding the paper with a large quantity.

The measures to be taken are: set up the ventilation knife to remove the gas generated during folding in time.

(4) eye position of pick needle in its mouth is damaged.

The main reason for this problem is that the picking needle did not retract in time during the folding process. At this time, it needs to adjust the retraction time of the picking needle. It needs to pay special attention to that the retraction time of the picking needle must be very accurate. If the time is too long, the paper will tear, and if the time is too short, the paper will lose control over a period of time, thus affecting the folding accuracy.

(5) when printing low quantitative light coated paper, the innermost sheet of book post is cracked.

The main reasons are as follows: 

① the printing drying temperature is too high, which makes the paper lose moisture and the paper brittle. 

② when folding, the pressure of the pinch roll is too large, which causes the paper to break or even break. 

The measures to be taken are: 

① set the printing speed and drying temperature as the best matching value during printing, and use the lowest drying temperature under the premise of ensuring ink drying;

② properly reduce the pressure during folding; 

③ install the folding auxiliary glue (water) spraying device on the offset press to wet and soften the inner paper folding.

The folding fault is caused by many factors, including not only the factors of the machine and raw materials but also the factors of personnel operation skills. This requires printing operators to grasp relevant knowledge, learn from each other, summarize carefully, and judge the problem in time and accurately, so as to take effective measures to reduce waste.