Trouble shooting analysis of Heidelberg M600 web offset press
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Fault: When the Heidelberg M600 rotary offset printing machine transfers 105g/m2 double-sided coated paper from 65g/m2 light coated paper, the back of the signature appears traces of dirt from the mouth to the tip. After careful inspection, it was found that there was a dirty phenomenon from the oven to the cooling unit, and the dirt inside and outside the oven was cleaned, and no effect was obtained.
Analysis: The most fundamental and direct reason is the quantitative change of the printing paper. Firstly, the tension of the paper strip is not increased enough. Secondly, the pressure of the platen roller and the platen roller and the air volume of the triangle plate are improperly adjusted.
Paper frame tension
The paper frame of M600 is zero-speed paper, the tension between the paper-storage rollers is the first tension, and the paper path between the paper-storage rollers is lengthened when the paper is fast-connected, which is convenient for paper-feeding in an instant; there is a secondary tension under the paper-storing roller. The roller is driven by a secondary tension motor, and is pressed against the platen roller (pattern rubber roller) to increase the pressing force of the paper; and then there is a regulating roller below to detect the tension of the paper tape, meet the printing requirements, and stabilize the second The effect of the secondary tension, improper adjustment of the adjustment roller will affect the overprinting accuracy; there is a correcting device behind the paper storage roller, its function is to control the paper strip into the left and right position of the printing unit, and has little effect on the change of the tension of the paper strip.
Printing unit tension
The tension of the tape between the printing units is the tension of the printing unit. The tension between the printing units is not adjustable during the printing process. The hardness, elastic deformation, plastic deformation of the blanket, whether the blanket belongs to the same brand, the newness and the thickness of the lining, the printing pressure of each group, the blanket The degree of tightness, etc., will affect the change in tension of the printing unit, causing ghosting and overprinting to be inaccurate.
Oven tension
The tension through the oven paper strip from the last set of printing units to the cooling unit is the oven tension, which is the longer section of the paper path. The size of the oven tension plays an important role in normal printing and is also the main cause of the above-mentioned scum problems. If the tension of the paper tape in the oven is not well controlled, it will cause paper breakage (excessive tension) and smudging (too small tension). The cooling drum rotation speed should be appropriately adjusted according to the quantitative, brittleness, toughness, etc. of the paper, and the pressure between the last cooling drum and the pattern rubber roller should be adjusted accordingly.
Paper guiding force
The tension of the paper strip from the cooling unit to the platen on the triangular plate is the paper guiding force. There are two sets of platen rollers. The pressure should be adjusted according to the quantitative or thickness of the paper. The pressure of the front group is higher than that of the rear group. The pressure roller (on the triangle) is slightly lighter or the same. The function of the platen roller is to maintain a constant tension in this section, and the pressure is generally 0.25 to 0.3 MPa.
Triangular tension
The tension of the paper strip from the platen roller to the pinch roller in the folder is the triangular plate tension. The pressure of the upper and lower two sets of paper-feeding rollers in the folding machine is twice the thickness of the printing paper. It is better to feel that the paper is not pulled by the hand and the paper tape is not broken. Once the adjustment is not good, the paper break will often occur. The adjustment of the air volume in the triangular plate can solve the smear caused by this part. The distance between the paper guide rollers under the triangular plate should be adjusted properly. According to the principle of symmetry, the tip of the triangular plate is used as the reference, generally 3 to 4 of the thickness of the printing paper. Double, otherwise it will cause the left and right deviation of the joint jam or the signature fold and the local smear when the paper is picked up.
In short, one of the distinguishing features of a rotary press differs from a sheetfed offset press in the adjustment and control of the printing tension. Grasping the tension can avoid the occurrence of many faults in the printing, and can efficiently produce high-quality prints.