Adjustment of the center distance of the drum
The adjustment of the center distance of the cylinder is a very important task, because the printing pressure is obtained by adjusting the center distance between the cylinder liner and the cylinder.
1. Working principle of roller center distance adjustment mechanism
The roller center distance adjustment mechanism has the following forms:
(1) The adjustment of the clutch pressure and center distance of the eccentric bearing type modern domestic offset printing press cylinder is mostly achieved by an eccentric mechanism. Its advantages are simple structure, convenient adjustment, accurate and reliable, but difficult to process.
The working principle of the eccentric bearing is shown in Figure 6-13. A shaft is eccentrically placed in the hole of the bearing, and the axis O1 and the rotation center O of the bearing are on the same horizontal line, and the eccentricity is Ï. If the eccentric bearing is rotated by an angle α around its center O, the position of the axis O1 will change accordingly. This is the basic working principle of the eccentric mechanism. Explain that the horizontal displacement and vertical displacement of the shaft center are not only related to the rotation angle α and eccentric distance Ï of the eccentric bearing, but also related to the circumferential relative position of the shaft center O1 and the bearing rotation center O. Therefore, the eccentric mechanism used to adjust the cylinder center distance (pressure adjustment) and realize the cylinder clutch pressure on the offset press has various requirements according to the cylinder arrangement form, and the circumferential position of the cylinder axis and the eccentric bearing center.
(Figure 6-10 Working principle of eccentric bearing)
Domestic offset presses are equipped with a set of eccentric bearings at the two shaft ends of the plate cylinder, whose main purpose is to adjust the center distance between printing and rubber, and two sets of eccentric bearings at the two shaft ends of the blanket cylinder. The outer eccentric bearing is used to adjust the center distance between rubber and pressure, while the inner eccentric bearing is used to control the clutch clutch pressure.
(2) Three-point support type (also known as three-point suspension type) The so-called three-point support means that the drum is supported by three support points at each end of the drum shaft.
As shown in Figure 6-11: The roller shaft 1 is installed in the rolling bearing, and the rolling bearing is installed in the steel sleeve 2, which is supported by three rollers (located at AA, BB, and CC, respectively). And the rollers 5 at AA and CC are mounted on the eccentric shaft 6. Turn the worm 4 to rotate the eccentric shaft 6 through the worm wheel 7, thereby changing the axis position of the roller to adjust the center distance between the rollers. BB is one Spring-loaded rollers, note the different labels).
(Figure 6-11 Three-point support structure diagram) [next]
The three-point support structure not only avoids the difficulty of processing the eccentric sleeve, but also has almost no precision requirements for the wall plate hole. The disadvantage of this structure is that it is difficult to install and adjust, and its seismic performance is poor.
(Figure 6-12 Center distance adjustment mechanism)
2. Adjusting mechanism of the center distance of the drum
The adjustment mechanism of the center distance of the cylinder of the domestic offset press is usually called "voltage regulator". As shown in Figure 6-12, the upper group is the pressure regulator of the plate cylinder, and the lower group is the pressure regulator of the blanket cylinder. The structure is basically the same. During adjustment, the shaft 1 is manually rotated, the screw 2 is driven, and the other is transmitted. A helical gear 3 on a shaft causes a sector gear 4 to rotate. The gear 4 and the eccentric sleeve 5 are fixed and rotate together, so as to adjust the center distance of the drum. In order to improve the accuracy of adjustment, the backlash of the meshing gear must be reduced as much as possible. The locking screw 6 should be loosened before adjustment and tightened after adjustment.
The direction (1) on the adjustment scale sign indicates that the center distance increases. (X) The direction indicates that the center distance decreases.
3 Measurement and adjustment method of the center distance of the drum
Domestic offset printing machines determine the center distance of the rollers by measuring the gap between the rollers and pillows to ensure the correct meshing relationship of the gears. Thick or thin gauges or soft lead wires are generally used to measure the rollers roller gap. Practice has proved. The soft lead wire rolling measurement is more accurate, and the effect of rolling the lead wire on both sides of the pillow at the same time is better. When measuring with a lead wire, place the lead wire in the gap between the pressed roller pillows and rotate the machine at a low speed. The lead wire is pressed into a sheet as the roller rotates, and then the thickness of the lead wire pressed into a sheet is measured, and then refer to the value given in the manual . Adjust the center distance of the drum.
For the printing machine without roller pillow and roller pillow contact, the distance between the two cylinders can be measured, and the measured distance can be determined with a special plug gauge.
Pay attention to when adjusting the center distance of the roller:
(1) Clean the dirt on the surface of the roller, so as not to affect the accuracy of the roller pillow gap measurement.
(2) Remove the roller pads and perform actual measurement without contact pressure of the roller.
(3) First adjust the center distance between the blanket cylinder and the impression cylinder, and then adjust the center distance between the plate cylinder and the blanket cylinder.
(4) After the adjustment, carefully check any three-point gap between the roller pillow and the surface of the roller. Make sure that the center distance and parallelism of the roller are kept correct.
[Related Links]
The micro-adjustment of the center distance of the cylinders of modern high-speed offset presses is done on the computer interface, and the basic principles are the same.
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