Printing skills and precautions by JCTPRINT

Printing skills and precautions by JCTPRINT

First, the performance of the ink:

 

1) Concentration: The ink with large concentration is used less in the printing, the ink color is better; the ink with smaller concentration is used more in the printing, the ink color is lighter;

2) Fineness: the size of the ink particles, the fineness of the ink, the concentration of the ink is large, the dots of the printed matter are clear, full and powerful; the fineness of the ink is low, the dots of the printed matter are easy to hair, and the printing durability of the printing plate is low;

3) Viscosity and viscosity are high, which may cause uneven ink transfer, dot pulling and stenciling; the viscosity is small, which may cause ink emulsification and plate surface floating phenomenon;

4) Mobility: The fluidity is large, the image will be unclear, the ink color will not be full; the fluidity will be small, so that the ink will not spread smoothly and unevenly, which may cause the front and the back on the same printing surface to be light or weak. Deep post phenomenon

5) Light resistance: ink with good light resistance, printed with beautiful color, full and solid image, full of three-dimensional sense, and can be stored for a long time; ink with poor light resistance, the color of the printed product is easy to become lighter and darker;

6) Water resistance, acid resistance and alkali resistance: For offset printing inks, special attention should be paid to their water resistance, acid resistance, alkali resistance, water and acid resistance and alkali resistance. The printed products are bright in color, clear in layers and clear in dots. Water-resistant, acid-resistant, alkali-resistant, poor ink, the printed products are gray and weak, the level is unknown, and the outlets are not clean.

Second, dampening water

The PH planting of dampening water is generally between 3.8 and 4.6. In actual production, it should be adjusted according to the specific conditions of printing conditions. If the dampening water is too acidic, the lipophilic foundation of the blank part of the plate and the graphic oil. Corrosiveness will increase, which will easily cause the pattern phenomenon, which will reduce the printing durability of the printing plate; at the same time, the ink will be easily emulsified, the ink roller will be deinked, and the printed matter will be dull.

If the acidity of the dampening water is too weak, the hydrophilic and oil-repellent properties of the blank part of the printing plate will be weakened, the layout will be dirty and the paste will be caused by the enlargement of the printed dots (when the ink is printed, if the dampening water is acidic and too acidic, The layout is easy to get dirty)

Third, the color sequence

The color sequence refers to the sequential printing sequence of each color printing plate in multi-color printing. Different color sequences will produce various printing effects, and it is important to arrange the color sequence reasonably. But the color order is not absolute, the color order is generally arranged as:

Monochrome machine: yellow → magenta → green → black two-color machine: black → yellow, magenta → green (print landscape) or blue → red (printed characters);

When there are gold, silver, and full-page printing, it is generally necessary to first apply gold, silver, and full-scale on-site, and then set the four-color ink after the ink is dried. Fourth, batch printing

1) Check if the specifications of the four-color film are consistent (four sets of film are complete);

2) Check the proof and check whether the graphic is complete;

3) Stabilize the water and ink volume to achieve a flat ink mark to ensure the same color of the same batch of printed ink;

4) Try to clean the blanket after less downtime or downtime (some papers can be placed)

Fourth, official printing

When printing officially, the operator should concentrate on:

(1) Look: look at the operation of the machine, see the color of the sample, the registration and the quality of the outlet;

(2) Listening: Listening to the sound of the machine, whether there is any abnormality, whether there is noise in the sensitive area of the machine vibration;

(3) Touch: Touch the parts of the machine that are prone to heat due to wear and tear, and whether there is significant temperature change;

(4) Smell: I heard that there is no electrical burning and other abnormal smells. (When printing UV ink, pay more attention to the power line of UV machine);

(5) Inspection: Check the condition of the printed products and the abnormality of the machine, find the problem, and eliminate it in time.

Fifth, how to identify the size of water

To identify the big difference in moisture, first look at the moisture in the layout. This depends on the experience of the operator. Generally speaking, the water is large, the amount of reflected light on the plate is strong, and the side view is brighter; on the contrary, the amount of reflected light on the plate is weak, and the side view is dark;

If the water is too large, you can also observe it from the following points:

(1) Using a cardboard to shovel the ink on the ink roller, there will be fine water drops on the cardboard;

(2) There are fine water drops on the water roller, and the ink roller group deinks or has water drops;

(3) After the water is turned off or the machine is stopped for a long time, the moisture of the plate is still not dried up;

(4) The imprinted dot is empty, and the ink is dull and dull;

(5) Water shadow or water drops at the tip of the blanket cylinder.

Sixth, control the water balance

Ink and water are not absolutely incompatible. In the actual printing process, the ink and water are squeezed by the rubber roller and the rubber roller, and they are fused together to emulsify the ink. There are two kinds of emulsified state of the ink: when the water is large, the hour is "water-in-oil"; when the water is small, the water-in-oil is formed.

In the offset printing process, the mastery of the ink-and-wash balance has a very close relationship with the normal transfer of the print, the depth of the ink, the accuracy of the color registration, the dryness of the printed matter, and the dirt. Generally speaking, the water is large, the ink is emulsified, and the ink color is light; the water is small, and the blank portion of the layout adheres to the ink to cause dirt. Therefore, offset printing to control ink balance is the key to printing.

Seventh, control the balance of ink and wash

To control the balance of ink and water, it is generally necessary to grasp the principle of less water and less ink. Less water means that the blank part of the layout is not sticky; the thickness means that the amount of ink is appropriately increased on the basis of less water. In the printing process, the most taboo point is that the water is big and big. When considering the amount of water, it should be based on the size and distribution of the layout image, the thickness of the imprinted ink layer, the nature of the printing paper, the performance of the ink, the running speed of the machine, the temperature and humidity of the workshop, the pH of the fountain solution, and the added in the ink. Auxiliary agents and so on.

Eighth, clean the blanket, the ink roller must be cleaned when changing colors

After printing for a period of time, paper, paper powder, ink and other dirt will accumulate on the blanket, which will reduce the quality of the printed matter. Therefore, the blanket should be cleaned in time, especially when the paper with low printing strength is used. The accumulation of paper powder is more serious, so it is more frequent to clean.

If the ink roller group is not cleaned during color change, it will affect the purity of the new ink color. Pay special attention when changing from dark ink to light ink. If the black ink is replaced by yellow ink, if the black ink is not cleaned, the yellow ink will be blackened, which will affect the quality of the printed matter. Therefore, the ink roller set must be cleaned when changing colors.

Ninth, the main factors of overprinting

Before and after overprinting is not allowed:

(1) Printing press

a. The earth adjustment disc locking screw is not fixed, or the M5 hexagon socket screw on the paper feeding arm is fixed tightly;

b. Whether the pusher seat copper sleeve is worn;

c. paper feeding teeth are worn;

d. The printing pressure is too small;

e. Gear wear;

f. The blanket is too loose and not tied.

(2) Paper

a. Paper cutting accuracy is not high;

b. The amount of water is too large when printing, and the paper is stretched.

(3) Other

a. There is a problem with the plate or the original itself;

b. The jammed stack is too high or the platen is too heavy and the jam is skewed.

The left and right sets are not allowed:

a. The left and right baffles are too tight or the left and right baffle screws are fixed;

b. The length of the paper jam is different;

c. The drum is tilted left and right;

Tenth, the cause of oil dirty

Oil can be divided into two categories: one is because the blank part of the layout is sensitive to the ink, which appears in a greasy state, commonly known as "greasy"; the other is because the ink is emulsified and evenly distributed on the plate with very fine particles, commonly known as " Floating dirty."

The causes of oil dirty are:

(1) Plate

a. The quality of the printed version is not high (the base is not good or the recycled version);

b. The exposure time is insufficient and the developer concentration is too low when printing.

c. The protective layer of the plate layout is not cleaned;

d. The blank portion of the plate is oxidized;

(2) Printing machine

a. The pressure on the plate is too light;

b. The pressure between the water rollers is too light;

c. The viscosity of the ink is too low;

d. The surface of the blanket is aged;

e. paper powder and paper wool wear plates;

f. Dampening solution pH is not appropriate.

Eleventh.the reason for the different shades of ink before and after

In actual printing, sometimes the ink color on the same screen is different in depth, but often the ink color is darker and deeper.

The reasons for the inconsistencies in the ink color are:

(1) Roller section

a. The drum gear or bearing journal is worn for a long time.

b. The roller journal is not concentric with the drum housing.

c. The plate roller and the plate are overstressed, resulting in a beating

(2) Ink roller section

a. Use aged ink roller surface aging

b. The ink roller has not been cleaned for a long time, and the surface area ink is not able to be inked.

c. The viscosity of the ink is too large

Twelveth, what is the ink stick, how to eliminate it?

The ink bar refers to an obvious deep strip of the axial direction on the plate layout and the printed matter when printed on the flat screen or in the field. It is commonly called "black bar" or "black bar".

The causes and elimination of the ink stick are:

(1) The drum gears are worn out for a long time and should be replaced with a new set of gears;

(2) The printing pressure is too high or the pressure between the plate cylinder and the blanket cylinder is too large. The appropriate pressure should be adjusted;

(3) Contaminants such as paper, ink, and the like are embedded between the gears. The dirt between the gears should be removed, and new gear lubricants should be added to enhance the cleaning and maintenance of the machine;

(4) The pressure between the plate and the plate roller is too large, and the pressure between the plate roller and the plate should be adjusted;

(5) If the surface of the plate roller is uneven or the roller core is bent or not straight, a new ink roller should be replaced;

(6) If the ink is too thin, an appropriate amount of 0# varnish should be added to enhance the viscosity of the ink;

(7) The paper is rough and the surface strength is poor. The blanket should be washed frequently, and 6# varnish should be added to the ink to reduce the viscosity of the ink and reduce the degree of powder removal and hair loss.

Thirteenth, the cause of the water bar How to solve?

The water bar refers to an obvious shallow strip of the axial direction on the plate layout and the printed matter when printing the flat screen or the solid print, commonly known as "white bar" or "white bar".

The water bar is generally caused by the water delivery part. The causes and solutions are:

(1) The pressure between the upper water roller and the main ink is too large, and the pressure between them should be readjusted to make it appropriate to relieve some pressure;

(2) The ink is emulsified, and the surface area of the water roller is too much;

(3) If the layout moisture is too large, the water supply should be reduced, the blanket should be cleaned, and the ink roller should be cleaned in severe cases;

(4) The dampening water is too acidic and should reduce the acidity of the dampening water.

Fourteenth, the reason for the flower version, how to eliminate?

The flower version means that the dots on the printing plate are reduced, empty, weak in fat, fine dots are lost, and the color is dim.

The cause and elimination of the flower version is:

(1) The pressure between the plate cylinder and the blanket cylinder is too large, and the thickness of the liner of the roller should be reduced;

(2) The pressure between the watering roller and the watering roller is too small (large water), and the pressure of the water roller and the water roller should be properly adjusted;

(3) The dampening water is too acidic, it should dilute the dampening water and reduce its acidity;

(4) If the amount of water is too large, the amount of water supply should be reduced;

(5) The viscosity of the ink is too large, a certain amount of varnish should be added to the ink to reduce the viscosity of the ink;

(6) The printed version has a pattern in the process of plate making and printing, and should be replaced with a new version.

Fifteenth, what are the reasons for the paste? How to eliminate?

The reasons for the paste and the elimination are:

(1) The pressure between the plate cylinder and the blanket cylinder is too large, and the pressure between the plate cylinder and the blanket cylinder should be reduced;

(2) The pressure between the plate roller and the plate should be too light, and the pressure should be adjusted (2.5-3mm);

(3) The pressure of the plate roller and the plate should be too heavy, and the pressure should be reduced;

(4) The acidity of the dampening water is too strong, and the acidity of the dampening water should be appropriately reduced;

(5) If the ink is too thin, add "0#" varnish to the ink;

(6) If the amount of ink is too large, the amount of ink supplied should be reduced;

(7) If the desiccant in the ink is excessively added, the ink roller should be cleaned to reduce the amount of desiccant in the ink;

(8) The printed version of the body is too thin and should be replaced with a new version.

Sixteenth, the back of the dirty reason and troubleshooting

The back smudging means that the newly printed sheets are stacked together, and the ink of the lower one is smashed to the back of the one sheet, causing contamination of the sheets.

The reasons for the dirty back and the elimination method are:

(1) If the ink is not dry well or the amount of ink is too large, an appropriate amount of desiccant and anti-adhesive agent should be added to the ink or the amount of ink should be reduced;

(2) If the stack of paper is too high, the stacking height of the paper should be reduced;

(3) The ink is not dry and the paper is too heavy;

Seventeenth, the cause of ghosting

Ghosting, commonly known as double-printing and ghosting, has two types: axial ghosting, that is, the imprint of the ghosting portion is approximately parallel to the axis of the roller; the circumferential ghosting, that is, the imprint of the ghosting portion is perpendicular to the axis of the roller.

Reasons for axial ghosting:

(1) The machine has poor precision and the bearing is worn.

(2) Axial displacement of the plate cylinder or blanket cylinder.

(3) The ink roller is tilted axially (or the plate roller is not matched with the original machine)

(4) Paper "Ruffled Edge"

The reasons for the circumferential ghosting are:

(1) The blanket is not stretched tightly

(2) The drum is not in place

(3) The machine has been used for many years, the roller gear, bearing wear or the gap between the three rollers is too large

 

More related information please contact with:

Melody Liang

Jinan Jinchangtai Industry And Trade Co., Ltd  

Add:Lushangshengjing Plaza Building B-1406, No.6 Qingfeng Road,

Jinan, Shandong, 250014, China

Tel:0086-0531-61300169

 

Fax:0086-0531-61300169

Mobile/wechat/Whasapp/skype:0086-18660813189

 

Email:[email protected]

 

http://www.jctprinting.com/