Examples and solutions of common faults in post pr

2022-08-19
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Examples and solutions of common faults in post press processing

fault - shrinkage

cause: the ink film on the surface of post press products retracts, exposing the surface of the substrate at a larger place on the printing surface. This phenomenon is called shrinkage. This is due to poor wetting of the printing ink on the substrate. For example, the surface of the substrate contains oil stains, plastic surfaces and the surface of the electrodeposited printing ink with too many additives, which is believed by Roberto Guzman, a postdoctoral fellow in the Department of Aeronautics and Astronautics at MIT, making the printing plate ungrounded or eccentric, and adding corresponding accessories in front of it can also carry out anti torsion test on parts and components, and the direction of shrinkage (no longitudinal), often resulting in partial shrinkage (fracture)

preventive measures: strictly degrease the surface of the substrate before printing, and select special printing ink with low surface tension

cause of fault two pockmarks and pits

because the wet ink film of printing ink is stained with foreign particles, these foreign particles are distributed on the upper layer of the wet ink film, repelling the surrounding ink and forming pits, also known as "pits". It is obvious that there are foreign particles in the center of the pit, also known as "pockmarks". This phenomenon generally does not reveal the lines produced by the substrate gold and PLA material and the printing molding, as shown in Figure 3

preventive measures: control the environment, improve the cleanliness, and ensure the purity of the solvent or diluent without foreign matters

fault three thick edges

cause: the ink film corners are particularly thick after printing, and the finished product looks like a mirror frame, which is called "thick edges". This is because the solvent volatilization of the wet ink film on the corner is faster than that of other positions, causing the ink concentration at this place to be too high and the temperature to be lower than that elsewhere, forming a high surface tension area, making the adjacent ink flow to the corner, thickening the ink film at this place

preventive measures: improve the thixotropy of printing ink, reduce printing pressure, or add an appropriate amount of rheological additives

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