Offset paper machine analysis (a)

1.2 Paperboard

The function of the paperboard is to accurately convey the paper from Feida to the rules. Paper does not allow relative sliding on the paperboard. This is the general guideline for adjusting the components on the paperboard.

1. Movement analysis of paper on paperboard. Paper in the feeder part is driven by differential pressure, so what drive is the paper on the paperboard? When a paper-feed failure occurs on the paperboard, it is usually necessary to check the elasticity of the cloth and the size of the pressure wheel. Why does this happen?

When you place an object on a smooth surface, you will find it easier to move it than it is on a rough surface. Put a heavy object and a light object on the surface of the same object. Finding heavy objects is more difficult to move than light objects. From this point of view, the pressure of the object and the smoothness of its contact surface determine the ease of movement of the object. The force that hinders the object is called friction. The drive of the paper on the paperboard actually uses the friction drive. Friction is equal to the product of the surface pressure (n) and the smoothness of its contact surface (friction coefficient u), ie

f=n·u

To make the paper not slide relative to the paperboard, there must be enough friction so the frictional conditions must be created on the paperboard.

The power that the paper drives forward comes from the paper feeding belt. At the same time, the paper drives the operation of the pressure roller, so the pressure roller has a friction force that hinders the paper from moving forward. Assuming that the friction force of the paper transport belt on the paperboard is f1=n·u (n is the pressure of the pressure roller). The frictional resistance of the platen to the paper is f2=n·u2. Other forces on the paper are negligible. The force on the paper is f=f1-f2=n.(u1-u2) Since the paper is moving at a constant speed on the paperboard, f=0 is u1=u2. Where u1 is the sliding friction coefficient and u2 is the rolling friction coefficient. In general, u1>u2, because the static friction between the paper and the cloth belt, that is not reached the maximum value of f1, which is always balanced with the f2, so the paper will not be on the paperboard in an accelerated state.

Through the above analysis can also be seen:

(1). The forward movement of the paper is independent of the pressure of the platen roller, that is, the paper will not accelerate or decelerate, no matter how large the pressure is.
(2). The function of the pressure roller is mainly to make a reliable contact between the paper and the cloth belt and generate enough static friction force.
(3). If the tape surface becomes very smooth, ie u1<u2, the paper slips on the tape.

2. The function and adjustment of various components on the paperboard. The components on the paperboard include the tying roller, guide plate, double sheet controller, paper feeding belt, paper roller, brush wheel, paper feed, suction hole, and paper pressing frame. The following detailed analysis of the role of various components.

(1). The role of the splicing roller The splicing roller is mainly used to guide the paper conveyed by the delivery nozzle to the feeding board. The horizontal lines on the splicing roller play an important role in increasing the friction, so as to prevent the tape and the splicing. Relative slip between rollers. There are two platen rollers on the take-up roller. Their role is to make the paper and the take-up roller contact reliably. The press time should match the transfer time of the delivery nozzle.

(2). The role of the guide plate guide plate is to guide the paper conveyed by the take-up roller to the feed plate. The degree of flatness can be adjusted with screws.

(3). How many sheets of paper under the double detector double detector? This issue is sometimes unclear, and the key issue is that it doesn't know what a double sheet detector is. The role of the double-sheet detector is to detect that each input paper cannot have two or more sheets, independent of several sheets below it.

Take 540mm wide paper as an example. Generally Heidelberg presses have a paper feed step of 200mm (the distance between paper feeds from two passes) is graphically represented as:

(Figure 1.10a)