First, the plate making problem
1. **No Overprinting Allowed**
When setting up the layout (imposition), if the graphic or rule lines are not properly aligned, it can lead to difficulties in achieving accurate overprinting during printing. To prevent this, it's essential to ensure precise imposition, especially when using high magnification for detailed work.
2. **Multiple Exposures Can Cause Issues**
If multiple exposures are necessary, poor overprinting may occur. It’s best to avoid multiple exposures unless absolutely needed. If they are required, use exposure paper and apply zone exposure to maintain accuracy.
3. **Virtual Edition Problems**
A "virtual net" issue can happen if the PS plate is not tightly attached to the film’s photosensitive layer. This can result in ghosting or blurring on the printed plate. To fix this, tilt the PS plate slightly, place a few sheets of paper underneath, and increase the exposure time.
4. **Shrinkage of Outlets**
This usually happens due to overexposure, high developer concentration, long development time, or high temperature. Adjusting these factors can resolve the issue.
5. **Loss of Small Dots and Poor Field Density**
These issues often stem from low image density or overexposure. Recopying the film and reducing exposure time can help improve print quality.
6. **Sticky and Dirty Printed Material**
Caused by underexposure, underdevelopment, or overexposure, as well as faulty developers or fogged film. Solutions include increasing exposure time, adjusting developing conditions, replacing the developer, or re-copying the film.
Second, **ink-related problems**
1. **Flying Ink**
Ink may scatter like mist from the ink rollers. Causes include high ink viscosity, long filaments, or static electricity in dry air. To reduce this, lower ink viscosity, add a debonder, control ink flow, slow down the printing speed, and install a static eliminator.
2. **Sticking**
The back of one printed sheet may get smudged by the ink on the front of the next. This occurs when ink penetrates slowly or the paper has poor absorption. Solutions include improving ink drying, reducing ink volume, and using better-absorbing paper.
3. **Paper Brushing**
During printing, the paper may fluff as it leaves the blanket. This is caused by high ink viscosity. To fix, add a thinner or adjust the adhesive content to reduce ink viscosity.
4. **Block Version**
Ink and paper dust can mix into a scum-like substance that sticks to the plate, blanket, and printed material. Causes include too much ink, incorrect viscosity, uneven pigment dispersion, or weak paper surface strength. Solutions involve reducing ink amount, adjusting viscosity, replacing pigments, cleaning regularly, and controlling paper dust.
5. **Powdering**
The ink on the printed surface may flake off in powder form. This is due to insufficient film-forming agents, excessive powder in the ink, or soft ink films. Adding a gloss paste with more resin and desiccant, or mixing with harder ink, can help improve adhesion.
Third, **blanket-related issues**
1. **Plastic Deformation of the Blanket**
Uneven pressure during printing can cause the blanket to deform, leading to thickness inconsistencies. Avoid excessive pressure, ensure proper tightness, and clean the blanket regularly to prevent buildup of paper fibers and dust.
2. **Blanket Tightness**
Too loose or too tight can cause ghosting or reduced elasticity. A newly installed blanket should be stretched gradually after some use to stabilize its tension.
3. **Torsion Deformation**
Uneven forces on the blanket can twist its shape, affecting print accuracy. Ensure roller alignment and proper installation of the blanket.
4. **Substrate Problems**
Paper quality greatly affects print results. Factors like moisture content, smoothness, pH, and surface strength all play a role. Proper humidity control and paper selection are crucial for consistent printing.
5. **Printing Machine Adjustments**
Modern offset presses like Heidelberg, Manroland, Komori, and Mitsubishi require careful management of water-ink balance, pressure, and speed. These settings must be adjusted based on the substrate and ink properties for optimal results.
In real-world production, additional challenges may arise, requiring further analysis and troubleshooting. Always stay attentive to the process and make adjustments as needed for the best outcome.
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