Causes and solutions of problems in flexographic printing quality

details make a difference! ! ! There are many factors that affect the quality of flexographic printing, and almost all are small details. But if we don't pay attention, these small problems will cause big trouble.

Missed print

1. Reason analysis

â‘  Dust adheres to the printing plate.

â‘¡ The printing pressure is not enough.

â‘¢ The printing plate is not flat, so that the lower part of the transfer blank.

2. Solution

â‘  Shut down to wipe off the dust on the printing plate and check whether static electricity is generated in the plastic film printing, because static electricity is very easy to attract dust.

â‘¡ Properly increase the printing pressure.

â‘¢Check the printing plate to ensure that the printing plate is flat.

Beard-like marks around the picture

1. Reason analysis

â‘  The ink dries too fast, the ink on the edge of the printing plate is sticky, the film of the printing material is separated from the printing plate, and the ink drawing phenomenon occurs on the printing surface.

â‘¡ The viscosity of the ink is too high.

2. Solution

â‘  Properly delay the drying process of ink to reduce printing pressure and minimize the occurrence of edge bands.

â‘¡Check and adjust the viscosity of the ink to dilute the ink to a suitable level.

Irregular stripes or tiny spots on the printed surface

1. Reason analysis

â‘  The ink of low viscosity gives too much ink.

â‘¡ The fluidity of the ink is poor.

â‘¢The film thickness of the substrate is uneven.

â‘£ The surface of the printing plate is in bad condition, especially the photosensitive resin plate is improperly stored.

2. Solution

â‘  Adjust to use ink with slightly higher viscosity.

â‘¡Use fluid ink.

â‘¢ Check the film material, replace with a film with a relatively uniform thickness, or replace a plate with low hardness to improve.

â‘£Replace the new version.

Poor overprint

1. Reason analysis

â‘ The drying speed of the front color ink is too slow.

â‘¡ The printing pressure is too large during the printing of the back color ink.

â‘¢ The viscosity of the back ink is too low.

2. Solution

â‘ Front color ink should use faster drying ink, or use quick drying solvent to adjust or print as thin as possible.

â‘¡ Light pressure should be used when printing with back color ink.

â‘¢Pay attention to the viscosity of the ink of the back color, generally higher than the viscosity of the front color, but if the drying effect between the colors is good, the same viscosity can be used.

Overprint is not allowed

1. Reason analysis

â‘  The pitch space is inconsistent, or there is a crest.

â‘¡ The tension of unwinding or unwinding is uneven, resulting in uneven transmission of the film.

â‘¢The film has ruffles, uneven thickness and gas in the material.

â‘£The joint of the film affects the overprint.

⑤The pressure of the previous color has been deformed by the ambassador's printed graphics

â‘¥The quality of the printing plate is not good and the thickness is uneven.

2. Solution

â‘  Shutdown maintenance, pay attention to adjust the crest.

â‘¡Check and adjust the tension of the receiving and discharging materials to ensure their balance.

â‘¢ Replace the film without ruffles or release the gas in the material.

â‘£Pay attention to the bonding of the joints and ensure a uniform.

⑤Adjust the printing pressure to match the printing pressure between the colors.

â‘¥Check the printing plate, grind the back part properly, or pad properly in a thin place. If the problem cannot be solved, the printing should be replaced.

Poor ink adhesion

1. Reason analysis

â‘  The wrong ink type is used.

â‘¡Excessive dilution of ink.

â‘¢The surface treatment of the film is bad.

â‘£ The ink has deteriorated.

2. Solution

â‘ Check whether the ink is suitable for the film type, and select the appropriate ink.

â‘¡ Add appropriate original ink, adjust the ink to adjust for printing.

â‘¢ Detect the surface tension of the film.

â‘£ Replace with new ink.

The back of the printed film is dirty

1. Reason analysis

â‘ Ink drying is poor or solvent remains.

â‘¡The accumulated or remnant heat of the drying equipment is stored at high temperature.

â‘¢ The winding tension is too large.

2. Solution

â‘  Increase the drying temperature or reduce the production speed.

â‘¡Ensure that the ambient temperature is suitable for printing requirements.

â‘¢ Avoid the excessive pressure of the printed product winding, you can use the offset printing powder before winding.

Pile of ink

1. Reason analysis

â‘  The printed version is of poor quality and uneven thickness.

â‘¡The quality of plate making is poor.

â‘¢ The pressure between the printing plate and the impression cylinder is too high.

2. Solution

â‘ Check the printing plate, if the thickness is uneven, you can grind the thick part properly; if the thin part is properly raised, the picture and text of the solid part and the thin text part should be raised on the solid part, if it is resolved If there is no problem, replace the good quality plate.

â‘¡Re-make the plate, pay attention to improve the plate-making technology to ensure the quality is qualified.

③ Speed ​​control to control the pressure between the plate cylinder and the impression cylinder. Under the premise of ensuring the printing quality, try to adjust the pressure to the minimum, that is, slight contact, to avoid squeezing the ink to the surroundings and the edge of the plate due to excessive pressure The ink is transferred to the film in a stacked state and the edge of the ink stack failure occurs.

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