Printing Problems and Solutions

Printing Problems and Solutions

1、 Deviation (i.e. lateral sleeve deviation):

It refers to two or more printing plates being asymmetric or overprinted during the printing process. Check if the shaft screws are not securely fastened or if the oven temperature is too high.

The main manifestations are: deviation in the same direction and deviation in the opposite direction

Handling method:

1. Notify other employees to place markings on semi-finished products;

2. Targeted pattern making, adjust the position of the pattern if any color deviation is found, and immediately mark it on the semi-finished product after adjustment;

3. If it is a frequent misalignment, it is necessary to check whether the plate is loose, whether the plate shaft fixing seat is locked, and if it is not locked, it needs to be re locked;

4. Adjust the temperature and pressure of each version. If both sides protrude, increase the temperature of the previous version, and if the opposite is true, decrease it. (Especially those that deviate in the opposite direction);

5. Observe the dry humidity and temperature in the workshop. If the temperature is high and the humidity is low, water can be sprayed onto the workshop floor to humidify and cool down. (Especially in the opposite direction).

2、 Longitudinal misalignment:

Reasons and solutions:

1. Check if the color code is clear and if there are any wrinkles on the paper. If there are any, immediately eliminate them.

2. Check the installation of the printing plate. If there is frequent misalignment, it may indicate that the printing plate is loose and needs to be stopped and re locked.

3. Observing from computer adjustment, the first step is to accurately measure the circumference of the printing plate. If it is due to errors between printing plates, fine tune the color chart.

4. Adjust the lens of the coil and the shooting plate.

5. Check if the shaft screws are not securely fastened or if the oven temperature is too high

3、 Unclear font and dots:

Reasons and solutions:

1. Ink sealing: (1) Clean the printing plate; (2) Add an appropriate amount of slow drying agent; (3) Reduce the viscosity of ink (decrease the number of seconds); (4) Replace the ink.

2. The angle adjustment between the scraper and the printing plate is not good: stop the machine for inspection, adjust the knife or replace it with a new knife.

3. Quality issues with printing plates or scrapers, such as wear and tear caused by prolonged printing time, require replacement in severe cases.

4、 Dragging knife:

It refers to the situation where there is ink or paper debris on the cutting edge, or where the printing scraper is worn or chipped.

Reasons and solutions:

1. Scraper wear: Replace with a new blade.

2. The angle and pressure of the scraper: adjust the angle and pressure.

3. Stick ink on the scraper: Clean the scraper or change the blade.

4. Ink powder is too coarse or ink dries too quickly: Add an appropriate amount of slow drying agent or reduce the viscosity (decrease the number of seconds).

5、 Drag the line

Reasons and solutions:

1. Stick ink on scraper: Use a bamboo stick to lightly pick it a few times (try to do it once at the beginning or end of each semi-finished product roll to avoid rewinding). If it cannot be eliminated, move the scraper far or near or adjust the pressure. If it still cannot be solved, change the knife or fix the knife holder. Caution!

2. If changing the knife cannot eliminate it, the viscosity of the ink should be measured. If the ink is coarse, the knife can be used with a blade back, but it should be noted that using a blade back will shorten the life of the printing plate.

3. If there is no problem with viscosity, check if the printing plate has been scratched. If it's serious, you need to change the version.

Attention: If the printing ink stops halfway, the base plate may be easily sealed. It is necessary to use ethyl grease to wipe the plate, and the pressure stick switch must be turned off before wiping. To control the ink seconds well, thin or thick ink on the surface can cause poor coverage.

4. If not, consider whether there are impurities in the ink. Use a funnel to filter out the impurities or replace the ink.

5. Check if the scraper is broken.

6. Black ink dragging is more common. In the solvent ratio, too much isopropanol can cause the ink to not completely dissolve, and particles can lead to stringing. If the bottom ink has stringing, a small amount of ethyl alcohol can be dissolved and diluted before use.

6、 Wrinkled paper

Reasons and solutions:

1. The quality of the original paper itself: If any problems are found, they should be removed and not printed.

2. The paper stick is stuck with ink: Clean the paper stick thoroughly, increase the temperature of the plate appropriately, clean the dust screen of the fan in the plate sequence, and increase ventilation.

3. Sticky Ink Wrinkle Paper: First, check which rotating axis sticks the ink, then use a scraper to scrape off the ink stuck on the stick, and then check the weight of the wrinkled paper before placing the label.

4. Pressure stick: Check if the air pressure of the cylinders on both sides of the pressure stick is the same. Increase the air pressure on one side of the corrugated paper of the pressure stick, or adjust the air pressure on the other side appropriately to make the air pressure on both sides parallel; If the wrinkling paper is caused by the deterioration of the adhesive stick, the bearing or the entire adhesive stick should be replaced.

5. Check if the tension during winding and unwinding is too high. You can reduce the tension and adjust it according to the needs of each variety.

7、 Blocked version (sealed version):

The ink on the printed pattern is incomplete, resulting in insufficient ink on the printed material. Some parts of the pattern cannot be printed, and the area remains unchanged. Mainly caused by ink drying and clogging the mesh holes in the gravure printing plate drum.

Main reasons: 1. Ink aspect. If the ink particles are coarse, the ink connecting material has poor solubility, high viscosity, or dries too quickly.

2. In terms of printing plates. Shallow mesh holes can also easily cause such malfunctions.

3. The rubber roller is not smooth and has grooves. Replace the rubber roller to solve the problem.

Handling method:

1. Generally, it is necessary to clean the printing plate, carefully soak the dry area with solvent, then dip it in dirty powder, gently rub it to suck out the ink in the mesh hole, and then clean it with solvent,

2. Use ink with finer particles to give it good transfer performance.

3. To improve the solubility of ink, choose solvents with good solubility and slightly slower drying speed, such as butyl ester (ethyl ester dries faster than butyl ester). If pure butyl ester also dries quickly, a small amount of slow drying agent can be added.

4. Attention should also be paid to reducing the temperature of the drying oven appropriately and preventing hot air from blowing directly onto the printing plate cylinder during operation.

5. When the rubber pressure stick is not smooth or has a concave position, it needs to be replaced.

8、 Partial loss of graphics and text:

During the printing process, it is common to encounter the phenomenon of partial loss of graphics and text, as well as defects.

Main reason: Generally, it is because the cohesive force of printing ink is relatively high, and the surface of the paper is relatively rough. Although some pressure is applied during printing, the ink in the printing small holes is still not easy to transfer to the substrate.

Solution: 1. Check whether the printing plate drum is blocked by mesh holes and whether the surface of the pressure roller is smooth and intact.

2. Increase the pressure on the rubber stick or use a lower hardness embossing stick

3. Reduce ink viscosity while increasing printing speed

4. Using materials with low surface roughness may have better results

5. Activate the electrostatic ink aid device

9、 Starting line:

Linear marks in the circumferential direction of blank areas in printed materials, which are common problems in printing. Generally, the cause can be identified on the printing plate, ink, and scraper.

main cause:

1. In terms of printing plates. The surface quality, smoothness, and hardness of the chromium layer (electroplated layer) have a significant impact on the formation of lines (insufficient polishing of the printing plate). Because the pigments in gravure ink generally exist in the form of particles, during the printing process, the ink fills the printing plate and is scraped off by a scraper, while constantly creating friction on the surface of the plate. If the hardness of the chromium layer on the layout is not high, it is easy to be scratched by coarse pigment particles and dents may appear. In severe cases, it can cause stringing. Another situation is that if the chromium layer has poor smoothness, it is easy to retain active substances in the ink, which are not easily scraped off even after being scraped by a scraper. When transferred onto the substrate, irregular and shallow lines are produced.

2. In terms of ink, drying too quickly, high viscosity, and coarse pigments can all cause incomplete ink scraping and the formation of streaks.

3. Scraper is a very important component in the printing process. When the inlet of the scraper is damaged and there is a gap, there will be regular left and right movement of ink marks on the product, which is relatively easy to identify.

Handling method:

1. In terms of printing plates

① If this type of problem is mild, it can be carefully polished with fine sandpaper (using 800 grit sandpaper);

② At the same time, the accuracy of the installation of the printing plate cylinder should be strictly controlled to prevent eccentricity from exceeding the standard, so as not to cause excessive impact on the scraper during high-speed printing, which is also beneficial for reducing the occurrence of lifting lines.

2. In terms of ink.

① Pay attention to selecting high-quality ink and matching solvents, and control the appropriate printing viscosity;

② At the same time, it is necessary to regularly check and clean the filtering device in the ink delivery system. It is best to use a sieve to separate it to prevent impurities and coarse particles from leaking into the ink and damaging the scraper and printing plate.

3. Fine knife notches can be polished with oilstone or fine sandpaper until smooth and even. If the notch is large, it needs to be replaced. During operation, it is important to control the angle and pressure between the scraper and the printing plate to reduce the friction of the scraper on the printing plate.

10、 Guiding stick adhesive ink:

The phenomenon is that the guide stick after coming out of the oven is stained with the color of the printed ink, which brings dirt to the product.

Main reason: Poor drying of printing ink.

Attention: 1. Check if the machine speed is too fast first;

2. Whether to turn on the cooling fan;

3. Is there too much slow drying agent added to the ink.

11、 Ink dots

Fingerprint brushes have a lot of ink falling or splashing on the substrate.

Handling method:

1. First, check whether the paper baffles on both sides of the printing plate can effectively prevent ink splashing or dripping during high-speed operation. If there is splashing, check if the baffle paper is damaged or if the cloth under the baffle paper is loose. Adjust the position of the paper baffle or replace it with a new one and use cloth to block the triangular area between the cardboard, printing plate, and knife. (Note: Do not insert your fingers into the printing plate area to arrange the cloth fragments. Use a bamboo stick to straighten or stop the machine to redo.)

2. The scraper failed to adhere tightly to the printing plate, causing ink to flow out from under the scraper. In the printing process, the total pressure on the scraper is the sum of the pressure required for the scraper to remove the ink from the surface of the printing plate and the pressure required for the scraper to resist the ink impact. As printing speeds up, the impact force increases accordingly. Therefore, when it is necessary to increase the printing speed during the printing process, the pressure of the ink scraper should also increase accordingly, otherwise ink is easily flowing out from under the edge of the ink scraper.

3. Check if there are any cracks on both sides of the scraper.

4. If there is dirt in the horizontal area, it is necessary to check whether there are foreign objects embedded in the scraper mouth, whether the pressure of the scraper blade is uniform, whether the blade is installed flat, and whether the scraping angle is appropriate. After finding the cause, adjust it accordingly.

12、 Color difference

Main reasons and solutions:

1. Ink sealing: Clean the printing plate with cleaning powder.

2. Plate bounce: Reinstall or replace the plate holder.

3. The pressure stick is unbalanced, with both heavy and light pressure: adjust the pressure.

4. Plate wear: Plate replacement

5. Quality issues in printing plate manufacturing, with deep edges and shallow edges: changing the plate

6. Appearance of yin and yang colors. If it is vertical yin-yang color: change the version. If it is horizontal yin-yang color, that is, one end of the printing plate is darker and the other is lighter: the pressure and angle of the scraper on the left or right side should be adjusted according to the color of the template.

7. The error of ink blending by operators: Firstly, it is necessary to correct the work attitude and focus on the work; Secondly, it is necessary to continuously accumulate experience and pay special attention to whether the quality of ink has changed.

8. Long term printing causes excessive wear and tear on the printing plate, resulting in localized copper layers: replace with a new printing plate.

9. Ink viscosity is low, resulting in a lower color; If the viscosity is high, it will make the color darker: control the ink within the required range.

13、 Ink Shadow

When an ink shadow is detected, first quickly and gently press the scraper, and then check if there is another ink shadow or if the scraper is pressed too tightly, causing dragging of the blade. If the problem still exists after treatment, the degree of wear of the scraper should be checked to see if it needs to be replaced.

14、 Ink not dry enough to stick stick:

Solution: 1. Increase the humidity of the oven;

2. Clean the filter screen of the fan;

3. Check if the inlet or outlet of the air duct is closed.

15、 When printing, the bottom and surface plates cannot be overlapped:

Raise or lower the oven temperature and pay attention to indoor humidity. If the left and right sides of the mask protrude, the oven temperature should be raised, and if the two sides shrink inward, the oven temperature should be lowered.

16、 One side of the printing roller wrinkles the paper:

Check if the air pressure on both sides of the cylinder is normal or if the pressure roller is worn.

17、 During the printing process, the font suddenly becomes thicker or does not meet the requirements

Solution: 1. Check if the viscosity of the ink is appropriate, as the ink is too thin

2. Check if the scraper is loose, lock it immediately if it is loose

3. If the above steps cannot solve the problem, check the wear level of the scraper, and if it is severe, replace it

18、 How to reduce the loss of raw materials in the production process

1. When trying ink, use leftover paper to test

2. Be careful not to let the forklift damage or collide with the raw paper when collecting it

3. In the process of ink testing, it is important to be fast and accurate, and the key is to master the ratio of various inks

4. Orderly conduct during the production process

5. Timely address quality issues

19、 How to effectively reduce the occurrence of quality accidents

Firstly, it is necessary to comply with the safety production management regulations and operate strictly according to the production procedures. Pay more attention, pick knives frequently, and scrape off the ink stuck on sticks.