Above we discussed how to determine a suitable printing pressure and how to adjust the printing pressure. Its purpose is nothing more than to ensure that the printing pressure is within a reasonable range during printing. In actual production, no matter whether the printing pressure is large or small, it will cause one or other problems.
If the printing pressure is too low, the ink cannot be transferred normally, the printed matter is empty on the Internet, and other printing defects. We are used to thinking that the printing pressure is large, then the transfer amount of ink will be larger, but the printing pressure and the transfer amount of ink are not in a proportional relationship in production. When the printing pressure is greater than a certain range, the transfer amount of ink can not only increase with the increase of the printing pressure, but will become smaller. At the same time, excessive printing pressure will cause the printed matter to increase the Internet access point or even spread. Excessive printing pressure will also damage the mechanical structure of the printing press. The more direct performance is the wear of the printing plate and the damage to the surface of the substrate. From the above we can see that the printing pressure is too small and too large are necessary in printing, it is very necessary to accurately guarantee a reasonable printing pressure.
Analysis of other common problems caused by printing pressure (the pressure expression mentioned below is the amount of rubber compression), the following discussion will mainly be based on mechanical compression.
Ink stick
cause:
(1) Ink sticks caused by serious roller gear wear.
1. Adjust the center distance too large;
2. Or the drum gear is seriously worn, and the gear backlash is greater than 1.0 mm. When the drum is pressed, the gears tremble, which causes frictional sliding on the surface of the contacted drum, and finally causes the dots to deform during the transfer process.
Solution:
1. Replace the new gear;
2. Properly reduce the center distance of the drum, and mesh the gears tightly so that the side clearance is less than 0.1 mm;
3. Adopt soft bag lining. The compression amount between the plate cylinder and the blanket cylinder should not exceed 0.1-0.15 mm; the pressure between the blanket cylinder and the impression cylinder should not exceed 0.15-0.2 mm plus the thickness of a sheet of paper.
(2) Ink sticks caused by serious wear of roller bearing gears. When the shaft head and bushing are severely worn, the gripper immediately yields after being pressed, causing sliding friction and producing deep ink bars. Solution: â‘ Replace the new shaft sleeve; â‘¡If it is an old-fashioned low-speed offset printing machine, you can tighten the rigid band on the plate shaft head.
(3) The pressure between the plate cylinder and the rubber cylinder is too large. The ink bar feature is the ink bar in the fixed area. The pressure between the printing plate and the rubber cylinder is too large. Under the squeezing action, the rubber cloth produces a large friction and sliding, which causes the dots to deform and form an ink stick. Identify whether the pressure between the two cylinders is too high, the obvious feature is the "pop" sound when the pressure is combined, and generally after printing to 5,000 sheets, the surface of the printing plate shines.
Solution: The pads of printing plates and blankets should be digitized. The thickness of the printing plate pad should be within ± 0.03 mm of the standard, and the thickness of the pad in the blanket should make the pressure as good as possible.
2. Vertical ghosting
cause:
(1) Improper closing of the roller. The ghosting feature is the appearance of several longitudinal ghostings at the start of printing. This is because when the roller is pressed once, it can not be fit once. When it needs to be completed several times, its pressure is different, and the amount of compression deformation of the blanket is also different, so that when the dots on the printing plate are transferred to the blanket, The imprints cannot overlap and produce ghost images. The main reason is that the roller clutch mechanism is worn or loose, or the pressure between the rollers is too large.
Solution: Check the roller clutch mechanism. Tighten the loose screws and replace them if they are seriously worn. If it is a pneumatic pressure-combined model, pay attention to whether there is air leakage in the gas path, or whether there is a problem with the compressor air pressure. When the pressure between the rollers is too large, the pressure of the rollers should be reduced appropriately.
(2) The blanket is too stretched. The ghosting feature is full-length or partial vertical ghosting. There are two situations when the blanket is stretched too loosely. First, the entire blanket is stretched too loose, so that the blanket cannot be reset in time after being pressed, resulting in a large area of ​​ghosting. Second, the blanket is cut off or clamped. Inaccurate, causing local tension too loose and causing local ghosting.
(3) The pressure between the rollers is too large. The ghosting feature is large area longitudinal ghosting. The pressure between the rollers is too large, especially when the combined pressure of the rubber roller and the impression cylinder is too large, the displacement of the blanket is large, and it cannot be completely reset after each transfer, and a large area of ​​vertical ghosting occurs.
Solution: When large area longitudinal ghosting occurs, you should check whether the pressure between the rollers is too large. If it is too large, the pressure between the plate cylinder and blanket cylinder should be adjusted to 0.1-0.15 mm, and the pressure between the blanket cylinder and impression cylinder should be adjusted to 0.2-0.25 mm.
3. Paste version, flower version
Cause: The pressure between the cylinders is too high, sometimes the pressure between the impression cylinder and the rubber cylinder is insufficient, and the pressure between the plate cylinder and the rubber cylinder is just right, the operator then adds a liner through the blanket, causing the plate cylinder The pressure between the blanket rollers is too large, which increases the friction.
Solution: When the above defects occur, check whether the pressure of the roller is too high.
â‘ Recalculate and check whether the roller pillow clearance is normal (old-fashioned domestic models should be re-measured by pressing the fuse between the rollers)
②Is it appropriate to measure the thickness of the blanket and printing plate (± 0.03?);
â‘¢ Check whether the blanket has local unevenness.
4. Unilateral outlets are empty
Cause: The influence of roller pressure. The center distance between the two ends of the drum, or the pressure at both ends of the drum, should be kept equal, but some machines will move from one side to the center, resulting in a lighter pressure on one side and unsatisfactory unilateral outlets.
Solution: Before checking the pressure adjustment, factors such as pattern, large water on one side, and light pressure on the inking side should be excluded.
First use the method of pressing lead wire to measure whether the pressure of the roller is consistent on both sides of the roller. If the pressure at both ends of the roller has an error of 0.05? Or more than the other side, it is confirmed that the pressure is reduced. Then remove the printing plate and blanket, and then measure the naked cylinder and correct the center distance.
5. Blanket sticker
(1) The transfer time between the roller gripper and the delivery gripper is incorrect. The paper rolls from the paper gripper to the paper gripper to the roller gripper to complete the printing process and is passed to the receiving gripper. There must be a certain handover time between them to ensure accurate overprinting and continuity of paper transfer. The handover time between the paper teeth and the take-up gripper is too short, which will cause the paper to lose control in an instant and cause the paper to stick to the blanket. Paper sticky blankets caused by this reason often occur in the second group of two-color printing machines and the last group of multi-color printing machines. In addition, this situation may occur in each color group of multi-color printing machines. .
(2) The pressure between the rubber cylinder and the impression cylinder is too large. In the printing process, excessive pressure will cause the paper to stick to the rubber blanket. Even if the gripping force of the roller gripper and the delivery bite (or transfer roller bite) is increased, this phenomenon also occurs from time to time, especially in the printing ink layer. Thicker, smoother coated paper is more common. This is due to the friction caused by excessive pressure and the surface adhesion is greater than the gripping force of the gripper. The paper sticks very firmly to the surface of the blanket, and it feels strenuous when peeled by hand.
Solution: Adjust the time for handing over the teeth and adjust the printing pressure.
6. The roller can't close and press
cause:
(1) Low speed clutch slips. Low-speed machine rollers can't close up, the common is the clutch (mechanical) crescent bump slip
Solution: (Mechanical) Remove the clutch, chisel a few diamond-shaped grids on the plane of the crescent block, or do the repair welding pile height treatment on the convex block.
(2) The roller is loose from the pressure against the mountain screw. One of the reasons why the high-speed machine can not close the pressure is the loosening of the "backward" screw from the pressure. The "backer" screw is installed on the wall plate of the transmission surface. After loosening, the roller will be excessively depressurized. At this time, the clutch on the operating surface passively supports the teeth and turns back. When the pressure is closed again, the electromagnet will push the active brace up, and the active brace cannot slip with the passive brace, causing the roller to not be closed. If this phenomenon is not discovered early, the solenoid coil will soon be burned. Sometimes the operator makes a wrong judgment and thinks that the electromagnet has failed. As a result, the replaced electromagnet coil will be burned out successively, causing losses.
Solution: When the roller is not closed, remove the protective cover and jog the machine to check whether the electromagnet is working. If it is burnt out, replace it with a new one. At the same time, check whether the clutch clutch pressure is too heavy. When the clutch pressure is excessive, the active supporting teeth cannot be engaged with the passive supporting teeth. At this time, the transmission mask shell needs to be disassembled and the roller clamping pressure "backward" screw is tightened in the direction of the instantaneous needle. When tightening, it can be tightened by 1 to 2 more turns, so that the active brace enters the brace of the passive brace with a margin of 0.1 mm, and then the "backer" screw can be locked.
7. Clutch shaft buffer
In the printing process, the working mechanism of the pressure and closing pressure is the eccentric bushing. The clutch movement is operated by the roller clutch pressure mechanism. However, due to mechanical wear and improper adjustment, the buffering action of the clutch shaft will occur after the drum is pressed. Its root is mainly on the roller clutch mechanism, this phenomenon mostly occurs after adjusting the pressure or replacing the liner. It is characterized by the first lap after closing, the three points of the clutch shaft, swing rod and connecting rod are not in line, and it will be practical after a few weeks of operation.
Solution: First, carefully adjust and measure the roller pillow clearance according to the machine's instruction manual, strictly follow the data pad, to avoid any increase in pressure and the buffering phenomenon of the clutch shaft when the pressure is closed.
(2) The wear of the pawls or supporting teeth makes the clutch mechanism lose its self-locking ability. When the pawls or supporting teeth wear out, due to insufficient closing pressure, the three points of the clutch shaft, swing rod, and connecting rod are out of line and lose their self-locking ability. Buffering phenomenon.
Solution: After the pressure is pressed, a line is drawn from the center of the clutch shaft, through the axis of the swing rod to the axis of the connecting rod. When the three points are not in a line, and there is a gap between the closing pressure and the backing, you can try to add a plug between the pawl and the brace. When the three points are in a line, it may be better than a little. Measure the wear data, and then use the method of repair welding pawl or teeth to solve.
(3) The loss of control of clutch shaft sleeve wear is like the reason that the shaft diameter of the roller and the bush sleeve wear cause sloshing, and the "ink bar" appears, causing the clutch mechanism to lose the control of its due accuracy, causing the clutch shaft to buffer.
Solution: Set or replace in time to remedy.
8. Problems that should be paid attention to when adjusting the center distance of the drum
During the adjustment process, you must pay attention to:
(1) The liner (including printing plate, rubber, woolen cloth, and liner, etc.) of the plate cylinder and blanket cylinder must be removed, and at the same time, the cylinder gap, roller pillow gap and gear gap should be measured under pressure.
(2) A cylinder (plate cylinder or impression cylinder) without an eccentric bearing must be selected as the reference. This cylinder must be calibrated horizontally at installation and at a vertical angle to the wall panel.
(3) When rotating the eccentric bearing of the rubber roller to the stamping position, it must be noted that the position of the eccentric bearings at both ends should be in the same direction. In this way, it is possible to avoid a misalignment of the axis of the rubber cylinder with the axis of the reference cylinder.
(4) For offset presses without roller pillows, the gear mesh clearance must be adjusted within the specified range, beware of the "top teeth" of the tooth root. For offset presses measuring roller pillows, adjust the gap between the roller pillows at both ends to the standard value and roll at the same time The pillow must be kept clean and round. Then select two ends and three points on the surface of the drum to check whether the gap between the drums is the same and ensure the parallelism of the drum.
appendix:
One Color Pad Printer//Usage and characters
- With sealed cup to protect environment , VOC volatilization reduced 86% and save ink over 25%.
- With coin aluminum structure ensure more stabilization and long life.
- Independent cylinder to drive sealed cup ensure removing ink completely. Make min Pressure to remove ink and prolong the life of sealed cup and steel plate;
- Both thick steel plates and thin steel plates installed , Choose according to customer requirements.
- Can print almost small size objects . So sold very nice in the world.
- Widely used in the industry field of cosmetics case, electron parts, Toys, plastics production, Housewares, gifts, decorations.
- Completely printing solution including ink and thinner , fixtures, steel plates, rubber pads provided when you send us samples;
Application fields
Electrons, hardware, autos, toys, gifts, Plastics, household appliances, artwork, stationery, adornment, cosmetic, commodity, sport goods, decorative lightings, woodwork, office supplies, Photo Materials, Kitchen utensils, Hotel supplies, Computer, Mobile, etc., industrial field.
One color pad printer //Advantage
- Using the dimensional modulating table, can be up and down, front, left, and rotation of the adjustment, which will help precise printing;
- T-slot structure, easy installation of fixtures and products;
- Hand pick and place workpiece, operating more handy;
- Microcomputer program control, the movement is more accurate and reliable;
- Test machine can be a single action adjustment, adjustment is completed, you can use the automatic mode of operation;
- Equipped with four counters, can effectively measure the number of products;
- Structure using die-casting aluminum, lightweight and solid.
- Independent Rubber pad up and down stroke and speed adjustment function;
- Sealed cup ink system, ink savings, and also to prevent the ink in the VOC emission into the air pollution of the environment, health protection of operating personnel;
- Sealed cup glide independent driving cylinder Blade pressure and Ink Removing Completely;
- Either use the tungsten steel ring, you can use a ceramic ring, and easy to replace;
- Temporary shutdown can prevent the ink to dry within the Sealed cup with INK function;
- World famous pneumatic components to ensure the long service life of machine;
- Rubber sliding shaft with hardened guide shaft grinding of high hardness, good abrasion resistance.
One Color Pad Printer
One Color Pad Printer,Semi Auto One Color Pad Printer,Electric One Color Pad Printer,Durable One Color Pad Printer
KC Printing Machine (Group) Limited , http://www.kcautopm.com