The streak is commonly known as "bar", the dark streak is called "ink streak", and the light streak is called "water streak".
Streaks are a difficult problem to solve in offset printing, especially when printing solid or spot colors, the appearance of streaks directly affects the printing quality.
The characteristics, causes and elimination of a trace
The streak is caused by the instant friction and slippage caused by the blanket, ink roller, water roller, etc. contacting the surface of the printing plate, resulting in the destruction of the balance of the relationship between the ink and the ink. Graphic, changed the shape of the dot and the thickness of the ink accumulation, forming a streak.
According to the obvious characteristics of streak marks, ink streak marks and white streak marks can be divided.
The dots in the area of ​​the ink streaks are irregularly enlarged, the dots are elongated, the text is embossed, and the ink color is accentuated, forming an obvious deep streak on the layout.
White streak, also known as water streak, refers to the irregular shrinkage of dots in the streak area, forming an obvious shallow streak.
According to the type of streak failure, it can be divided into gear streak, vibration streak, roller streak and other factors.
The way to check the streak is: use a 50% dot screen to print on the coated paper with thin ink, and observe whether there is a streak.
Streak faults often occur when the machine is installed in the trial operation stage or the machine is out of repair. The modern high-speed multi-color offset printing machine has rarely seen streaks during the printing process. 8-1).
Table 8-1 Characteristics and identification of the marks, causes and solutions
Category characteristics and identification causes and solutions Rack marks 1. Streaks appear on the entire layout, resembling a rubbing plate. The first streak is 10 mm from the gripper and is fixed on each sheet. (1) The pressure of the inking roller against the printing plate and cross-ink roller is too large. (1) The pitch of the rack marks is consistent with the pitch of the ink roller gear. (2) The precision of the ink distribution gear is poor, and the part that has the greatest impact on vibration is detected. (2) The pitch of the rack marks is consistent with the pitch of the drum gears. (3) The installation and pressure of the impression cylinder are too large. (4) The accuracy of the drum gear is poor. Change the gear position. (3) There are 5 to 8 rack marks in a fixed position. (5) The reciprocating motion of the ink transfer and cross-inking mechanism is not properly matched with the printing time or there is a gap at the shaft end. (4) There are 2 to 3 rack marks in a fixed position. (6) Impact caused by cam mechanism or other problems. There is a problem with individual gear teeth, or inclusion of foreign objects. Roller streaks 2. There are ink streaks after the roller is depressurized. (1) The gap between the drum journal and the bearing is large. (1) The color of the ink on the front and back of the printed matter is inconsistent. (2) The roller is unbalanced and eccentric. (2) In one ink streak of the printed product, the thickness on the left and right is inconsistent with the middle. (3) The roller is unbalanced. 3. There are still ink marks after the roller is pressed. (1) There is a problem with the arrangement of the rubber roller and the diameter of the ink roller. (1) The color of the ink on the front and back of the printed matter is inconsistent. (2) The ink color is heavier, the stripe band is wider, the spacing of the ink stripe is small and even, and the position is not fixed (Place the paper on the impression cylinder and find the occurrence of the stripe on the machine correspondingly according to the position where the stripe is generated The cause of the mark). (3) The gap between the ink roller shaft and the bearing is large. (4) Ink roller accuracy: eccentricity, bending, deformation. The balance of each ink roller is not good. (3) Ink marks appear on the front of the blanket. The width of the strip surface is equal to the circumference of the rubber roller. (4) The pressure of the inking roller is large. (4) The position of the streak is fixed, and the ink color is heavy first and then gradually reduces menstruation. (5) Large rubber roller hardness 4. Wetting system problem (1) The contact pressure between the water roller and the printing plate is too large. (1) Most of the white streaks appear on the graphics of the mouth and the position is relatively fixed. (2) The transmission gear of the water string roller is seriously worn. (2) A white streak occurs in a certain area when printing the ground. (3) Improper adjustment of the water transfer roller. (3) White streaks appear in the printing area and are fixed. Vibration streak 5. The position of the streak on each sheet is fixed, and the width of the streak is the circumference of the rubber roller. (1) There is an impact when the plate cylinder and rubber cylinder come into contact. (1) Appears in the second half of the page after the middle of the paper. a The pad is too strong. b The plate at the contact area of ​​the cylinder is raised, or there is a transitional slope at the neutral position. (2) Appears in the front half of the paper. The distance from the front end of the streak to the gripping mouth is consistent with the distance from the impact point of the blanket cylinder and the impression cylinder to the beginning of the impression. (2) The gap between the drum journal and the bearing is large. a Adjust the center distance between the rollers. b Print with roller pillow contact. (3) There are ink streaks in the local area of ​​the printed matter, and the position rule is uncertain. (3) The impact of the mechanism prone to impact is transmitted to the impression cylinder, and vibration occurs in the printing part, which directly changes the printing pressure. a Eliminate the irregular vibration of some institutions. b Printed with contact roller pillow. [next]
2. Other causes of streaking
(1) The rubber blanket with poor quality is more likely to produce ink streaks than the high-quality, flat blanket, and the air cushion blanket is better than the ordinary blanket.
(2) Liner The hard liner has a good printing effect, but it is very sensitive to the accuracy of the machine and is prone to streaks. The printing pressure of blanket cylinder and plate cylinder is small, which is easy to produce ink streaks.
(3) The printing plate mesh plate has high friction and is not prone to ink sticks, but the field version and the thin line version are easy to slide, especially the large area of ​​the field version, the thin line version is most prone to ink streaks.
(4) Paper with high paper smoothness is prone to ink streaks. Example: Aluminum foil paper, high-quality coated paper.
(5) Thick inks with large ink viscosity are not prone to ink streak marks, while thin inks with large transparency have obvious ink streak marks. In addition, the type of ink also has an effect on the appearance of ink sticks. Black ink and blue ink are prone to ink sticks, while yellow ink has a color tone similar to that of paper, and the ink streaks are not obvious.
Three about ghosts:
Ghost image refers to different dark tone images of the same color block in the finished product. The initial cause of ghost images is often improper imposition. Put images that are not in a hue on one layout. Because different hue requirements are different, calibrating the hue of an image will destroy the hue of another image on the same layout, especially when the layout is crossed horizontally and vertically. One problem is particularly prominent. For example, when the dot density of CMYK is between 50% and 70%, the printing adjustment is not in place, and ink sticks similar to ghosts are also prone to appear.
Mommy Backpack
There are three modes to use the big diaper bag. It can be on the back with shoulder straps. It can be a diaper bag tote with handle straps. And with stroller strips, the diaper bag for dad and mom can be hanged on the stroller.
Best Mom Backpack,Biggest Diaper Bag Backpack,Baby Backpack For Mommy
Longzhao Technology (Guangdong) Company Limited , https://www.gdprincebag.com