Problems and countermeasures related to accuracy in plate making process

The reasons that affect the accuracy of plate making are generally summarized as follows:

1. Wire mesh, including the type of wire mesh used, the height of mesh, the fineness of wire diameter, the size of the opening area of the wire mesh, the size of the expansion rate of the wire mesh, the spinning method of the wire mesh and the color of the wire mesh.

2. Net frame, including the material, size and strength of net frame.

3. Tension.

4. Selection of tension angle.

5. Bonding method of mesh frame and wire mesh.

6. Pretreatment of wire mesh.

7. Scraper material, scraper width, hardness, scraping angle, edge state, screen distance, scraping pressure, etc. are all very important. Polyester rubber should be used to make scraper. The hardness of the scraper is mostly within the range of shore a60-80, the scraping angle is 20-30 degrees, and the cutting edge must always be flat and sharp. The screen distance is generally 2-4mm and the screen plate is parallel to the table. The scraping pressure is suitable for printing clear graphics.

8. Photosensitive materials, including sensitivity, resolution, adhesion, expansion, thickness, hardness, water resistance, solvent resistance, friction resistance and printing resistance.

9. The mixing time of photosensitizer and the time after mixing.

10. Drying methods and conditions, including drying temperature, humidity and drying time.

11. In terms of plate printing, the type of light source used, the length of exposure time, the distance of light source, etc.

12. The density of the negative film obtained by photographing.

13. Development, including: development methods: water development, warm water development, drug development; development conditions: temperature, soaking time, type and use of water sprayer, etc.

14. Drying temperature and time after development.

15. Selection of secondary exposure time and revision.

Representative problems and solutions in the process of plate making.

1. The image resolution is low and the level is lost.

Causes

(1) When printing, the substrate and the film contact is not solid.

(2) The quality of the base plate (positive picture) is not good.

(3) The quality of photoresist is poor and its resolution is low.

(4) Improper selection of light source.

(5) Mesh count too low.

(6) Improper development processing.

Solution:

(1) Use vacuum adsorption or other methods to make it close to each other.

(2) Check the substrate density and image quality.

(3) High quality photoresist is selected.

(4) Use a light source that matches the spectral wavelength of the photoresist.

(5) Increase mesh size.

(6) Check development flushing procedure and adjust water pressure and temperature.

2. Poor edge definition.

Causes:

(1) When printing, the substrate and the film contact is not solid.

(2) Insufficient development and development.

(3) Scattering of exposure light lines.

(4) The photosensitive film is not evenly coated.

(5) The number of mesh selected relative to the image is too low.

Solution:

(1) Use vacuum adsorption or other methods to make it close.

(2) Wash the image from both sides until it is clean and clear.

(3) Use colored wire mesh.

(4) Check the coating process and increase the wire mesh tension.

(5) Increase mesh size.

3. Thin lines and small dots disappear.

Causes:

(1) When printing, the bottom plate and the screen adhesive film do not fit properly.

(2) The density of the substrate is insufficient.

(3) The exposure time is not long.

(4) The illumination of light source is uneven.

(5) Insufficient development.

(6) The residual solution of the photosensitive pulp is opened into a transparent impermeable layer, which blocks the screen plate. Images can be seen on the screen plate, but no patterns can be printed. It is often seen in small dots, lines and pattern edges with high mesh number.

Solution:

(1) Improve the vacuum of the vacuum printer.

(2) Select high density film to make photographic image and text plate.

(3) Reduce the exposure time, or increase the distance between the light source and the exposed body.

(4) Choose a point light source with a dark box.

(5) Develop fully.

(6) When developing the plate, pay attention to the details to be flushed through. After the plate is flushed, quickly absorb the residual liquid. If possible, blow through the mesh with high-pressure air pump.

4. The plate produces bubbles.

Causes:

(1) The photosensitive adhesive is not evenly stirred before use or there are bubbles in the photosensitive adhesive itself.

(2) There is a lot of dust in the plate making environment, and there is dust on the screen plate film.

(3) The speed of coating photoresist is uneven or too fast (gas remains in photoresist).

(4) When printing, there is dust on the plate making film.

Solution.

(1) Before coating the photoresist, mix the photoresist with glass bar or wood bar, or add defoamer properly.

(2) Pay attention to the degree of dust in the air of the plate making environment, try to reduce dust and prevent dust from falling in.

(3) In the coating, to keep the coating speed uniform, on the other hand, the scraping speed should not be too fast.

(4) When printing, the screen should be clean and dust-free, which is also an important aspect to avoid bubbles.