The magic of tangent cutting in offset presses
When printing thin paper, the paper is prone to drilling under the double-sheet control wheel and the side gauge pull wheel. Many printers do not need the double-sheet control mechanism, and some put a piece of transparent glue on the notch of the paperboard under the side gauge pull roller.
The surface looks like the paper is thin, so it is easy to drill the paper. In fact, it has nothing to do with the thickness of the paper, but it is related to the cutting line.
In the printing process, the paper of the offset press inevitably interacts with the tangent line: there are tangent lines during the handover process, as well as tangent lines during the paper transport process. Today I will focus on the tangent lines that affect the paper transport and positioning.
1. The tangent under the double-sheet control wheel.
2. The side gauge pulls the tangent under the paper wheel.
Legend: Bearing: represents the roller (0709-10) in the double-sheet control mechanism and the paper-pulling bearing in the side gauge.
Pulling wheel (roller): represents the bearing in the double-sheet control mechanism and the pulling wheel (0601-31) in the side gauge.
Paperboard: represents the iron plate (0709-27) in the paper feeder, and the paper guide (0601-48) in the side gauge.
The pulling roller (roller) is generally positioned. The bearing is movable back and forth, the bearing forms a tangent line a--a at the position of OA, the bearing forms a tangent line b--b at the position of OB, and the bearing forms a tangent line c--c at the position of OC. (Pictured)
If it is line b--b, there is basically no drilling paper phenomenon, but sometimes due to the problem of the paper itself (such as ruffles, etc.), the drilling paper phenomenon will also occur.
If it is a-a line, then there will definitely be a phenomenon of drilling paper, because the tangent between these two rounds has a driving force to drill down on the paper (regardless of whether it is a lotus leaf edge, unless it is very thick paper, hard Lift it after touching, but then the time when the paper reaches the front gauge will be affected).
If it is the c--c line, then there must be no paper drilling phenomenon, because the tangent line between these two rounds has an upward force on the paper, so that the edge of the paper skips the gap and then hits the board, so the paper feeding process smooth.
We understand the impact of tangent on paper, so how can we grow our strengths and avoid weaknesses?
The roller of the double-sheet control mechanism itself cannot be moved. Only by borrowing the support (0709-18) to reach the position of the tangent line c-c, but sometimes it cannot be reached: after taking care of the tangent line, sometimes the two wheels cannot be contacted, so that the two wheels are in contact It cannot reach a reasonable tangent state. The shaft of the double-roller-controlled roller should be designed as an eccentric shaft so that it can be adjusted.
The principle of the side gauge is the same, but the upper wheel of the side gauge is a bearing, and the bearing shaft is eccentric. Although this eccentricity is not used to adjust the tangential position, when adjusting the gap under the side gauge plate, we should make the eccentric shaft The upper bearing and the paper pulling wheel form a tangent line that is beneficial to us, so that when the side gauge pulls the paper, the phenomenon of pulling the paper will not appear.
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