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Flexography has developed rapidly in China, and the technical capabilities of various manufacturers are uneven. Various problems often occur in the printing process. This article is the experience summarized by a professional flexographic technician in handling customer complaints, and is now shared with everyone.
Case 1: Pasting/Blocking, Phenomenon: Excessive ink sticking on the side of the printing plate image or text, or blocked word grooves.
Reason:
Ink A is evenly distributed. It is recommended to use ink with good dispersibility.
There are impurities in ink B. It is recommended to filter the ink.
C text, patterns, and dots are not suitable for printing. Suggestion: Consider the printing capacity of the printing machine and redesign it.
Improper pressure on the ink bucket roller. Suggestion: Use reasonable pressure.
E. The pressure between the Anilox and the printing plate, or between the printing plate and the substrate is adjusted improperly. Suggestion: adjust the pressure reasonably.
Ink from other units is threaded onto the printing plate. Suggestion: Adjust the drying state and solvent volatility between different color groups.
G ink has high viscosity and a large amount of ink passing. Suggestion: Reduce the viscosity.
H ink dries too quickly, blocking the printing plate's word groove. Suggestion: Add slow drying agent appropriately
Relationship with printing plate:
1. The printing plate relief is too shallow. Suggestion: It is best to use a bisection method between the printing plate relief and the base. For example: KY394JM-A base 2.00MM.
2. The gaps between fonts are tight and the contrast is too light. Suggestion: Check the film blackness and reduce the main exposure time or mask some printing plates.
Case 2: Image and text bleeding. Phenomenon: The pigment in the pattern is dissolved and diffused.
Reason:
Poor drying of ink A. Suggestion: Use appropriate solvents.
B is affected by the plasticizer or fuel in the printing material. Suggestion: Avoid using fuel based colorants.
Stability of C ink (dispersed before printing). Suggestion: Stir thoroughly before use or replace with ink with strong stability.
Relationship with printing plate: None.
Case 3: Adhesion, phenomenon: Two surfaces adhere to each other (rubbing dirt)
Reason:
Poor drying of ink A. Suggestion: Use a complete drying system.
Improper use of solvent B. Suggestion: Use appropriate solvents for balance.
C receives the material in the hot roll state. Suggestion: Cool the printed material before rolling.
D Excessive winding pressure. Suggestion: Reduce the winding pressure.
Relationship with printing plate: None.
Case 4: Hairing, Phenomenon: Irregular burrs in the graphics and text
Reason:
A The pressure between the Anilox and the printing plate is improper. Suggestion: Adjust the pressure.
B layout ink dries quickly. Suggestion: Cover the ink fountain and use appropriate solvent.
C printing plate reuse is not clean. Suggestion: Clean the printing plate before use.
Damaged D printing plate during cleaning. Suggestion: Use appropriate cleaning agents.
Improper pressure on the ink bucket roller. Suggestion: Adjust appropriately.
F The Anilox does not match the plate. Suggestion: Replace the Anilox or printing plate (depending on the printing pattern).
Improper viscosity of G ink. Recommendation: Replace the Anilox.
The surface of the H substrate material is rough. Recommendation: Replace the Anilox.
Relationship with printing plate:
1. The pattern is blurry. Suggestion: Check if the film is qualified and increase the exposure time.
2. Improper debonding of the printing plate. Suggestion: Fully debonding the printing plate.
Case 5: Lack of printing, phenomenon: unclear fine lines and dot prints, white spots in the pattern, and curved lines.
Reason:
The imprinting force of A is too light. Suggestion: Increase stress appropriately.
Poor adjustment of printing machine B. Suggestion: Adjust the printing mechanism to ensure balanced operation.
C printing plate scrolling jumps. Suggestion: Check the ovality of the printing plate cylinder and gear.
Excessive ink transfer in D. Suggestion: Control the ink transfer amount.
E ink has high viscosity. Suggestion: Reduce ink viscosity appropriately.
F The thickness of the Double-sided tape is uneven or there are bubbles when the plate is installed.
Missing dots/bent lines in G printing. Suggestion: Consider the compatibility between the ink solvent and the plate.
Relationship with printing plate:
1. The printing plate image is missing. Suggestion: Check if the film is qualified or increase the exposure time.
2. The thickness of the plate is uneven. Suggestion: Use qualified plates.
3. The washing time is too long or the brush is too hard. Suggestion: Use an appropriate washing time and replace with a more commonly used brush.
4. The hardness of the printing plate is related. Suggestion: A dot fine line printing, using a higher hardness, such as KY394JM-AShoreA38 ° (for cardboard printing). B Use elastic pads. C Use more elastic Double-sided tape.
Case 6: Bubbling. Phenomenon: Ink bubbles.
Reason:
It is recommended to use appropriate defoamers for the internal friction of ink A.
B The peripheral speed of the ink bucket roller is equal to that of the Anilox. It is recommended to reduce the speed ratio of the two.
There is excessive fluctuation in the C ink cycle, it is recommended to check the oil pump impeller and gear.
Relationship with printing plate: None.
Case 7: Printed materials become brittle. Phenomenon: The printing surface is damaged when bent.
Reason:
The high heat in the drying system reduces the moisture and plasticizer in the substrate.
Suggestion: 1. Control the temperature of the material roll. 2. Supply water vapor after drying. 3. The substrate passes through the wetting chamber.
Relationship with printing plate: None.
Case 8: Ink coverage is light and sometimes heavy. Phenomenon: There are vertical stripes on the printed pattern.
Reason:
A ink transfer system has poor ink transfer and low ink flow. It is recommended to increase the ink flow rate appropriately.
Excessive use of defoamer B. Suggestion: Use defoamer reasonably.
Relationship with printing plate: None.
Case 9: Inaccurate pattern overprinting. Phenomenon: Misalignment and unclear layering of printing patterns.
Reason:
A. The thickness of the mounting tape is inconsistent. It is recommended to use double-sided tape with consistent thickness.
The diameter of the B version roller is different. Suggestion: Check if the diameter of the plate is consistent.
The C installation technology is poor, and it is recommended to pay attention to the installation and positioning.
D substrate stretching/shrinking, suggestion: pay attention to the feeding mechanism and temperature.
E bearing body is dirty and worn. It is recommended to clean the bearing and replace it with a bearing with greater wear.
Relationship with printing plate:
A plate making film is not aligned. Suggestion: Correct the alignment of the film.
The thickness of version B is inconsistent. It is recommended to use the same brand and model of plate material.
The drying temperature of C plate making is high and there is no response. It is recommended to use a temperature of around 65 ℃ to dry the plate and then let it sit at room temperature for a period of time before continuing the plate making process.
When making plates, consider the length of the plate making time for each color. It is recommended to determine whether to appropriately extend the main exposure time based on the distribution of images and text.
Case 10: Poor ink coverage, phenomenon: spots and striped markings.
Reason:
Ink viscosity is low. Suggestion: Increase ink viscosity appropriately.
Ink B dries too quickly. It is recommended to add a slow drying agent appropriately.
The C quantitative roller is damaged. It is recommended to replace the quantitative roller.
D The Anilox is damaged. It is recommended to replace the Anilox.
E scraper is worn, suggestion: increase ink flow rate.
There are impurities and oil stains on the G substrate. It is recommended to check the substrate.
Relationship with printing plate:
Excessive debonding during plate making. Suggestion: Control the debonding time.
The cleaning/wiping of version B is poor. It is recommended to clean the plate (with residue) and replace the plate washing water.
Case 11: Printing something on the part without a pattern.
Reason:
The A-mount is too loose, it is recommended to install it tightly.
When pasting, there are bubbles or dirt underneath. It is recommended to clean the back of the plate and the base of the hanging plate and pay attention to the problem of bubbles.
There is deformation in the base of the C hanging plate film. It is recommended to use a stable quality hanging plate adhesive.
D The adhesive tape is poor, and it is recommended to use a sticky Double-sided tape.
The printing pressure is too high. Suggestion: Reduce the pressure appropriately.
F ink dries too quickly, it is recommended to add a slow drying agent to the ink.
G paper, dust, dirt, suggestion: check the substrate.
Relationship with printing plate:
Negative film density is low. Suggestion: Use a reasonable negative film density.
The printed text is too light. Suggestion: reduce back exposure.
Insufficient washing time for C/insufficient brush pressure. Suggestion: Adjust the brush distance and use a reasonable washing time.
Case 12: Stripes appear at the beginning and end of the image and text, and the phenomenon is edge warping.
Reason:
A has no edge sealing. Suggestion: When pasting, pay attention to the edges being tightly attached or adding edge sealing adhesive.
Insufficient adhesion of the B-mount adhesive tape. Suggestion: Pay attention to the adhesion of the adhesive tape.