Common defects in printed products - flat screen printing (1)

Different printing process equipment, there are some differences in the production of printed defects, the following from the flat screen printing, rotary screen printing, roller printing, respectively, the name of the defects in the printing products processing, form, cause and prevent method. Since the vast majority of printing defects are difficult to repair, in order to improve the quality of products, the principle of prevention should be implemented in production to try to improve the technical level of operators.

One, the common flaws in flat screen printing

Most printing defects originate in multiple processes. The defects that have already appeared in the front are not repeated here.


(I) The defects caused by plate making

1. Plug (blocked version)
(1) Form: The type of printing on the fabric is incomplete and the color is uneven. Such as unclear outlines, broken stems, incomplete mud, fuzzy blocks and so on.
(2) Cause:
1 Black and white manuscripts are not enough, and they are not covered tightly, resulting in a certain degree of exposure and blocking the network.
2 When flushing, flushing is not clean, leaving part of the photoresist at the pattern.
3 The surface of the grey fabric is not clean, so that the impurities such as hairs are stuck on the floral plate, resulting in blocking the net.
4 Impurities in the color paste result in uneven feeding.
5 Paint printing, inaccurate or stop printing for too long, and the adhesive is slightly cross-linked and blocked.
6 When the manual platen printing, the platen temperature is too high, the printing speed is too slow, the color paste is dry on the screen and the net is blocked.
(3) Preventive measures:
1 Select the ink with strong coverage of the draft.
2 Wash flowers carefully and carefully.
3 Strengthen the pre-processing of semi-finished products and check before printing. Too much fabric can be treated by singeing first.
4 Check the floral version carefully before printing, paying particular attention to the phenomenon of blocking. Blocked nets were discovered and dealt with promptly. When preparing the color paste, the original paste must be filtered. If the paste is crusted after it has been placed, it may be filtered before it can be put on the machine.
5 Paint printing should use adhesives that are not easily crosslinked at room temperature, such as special screen printing adhesives. Blocked nets were found during printing and should be promptly cleaned up.
6 When printing fine patterns on a hot platen, always wash plates. In general, when the pattern is scraped to both ends, several blank plates are scraped on the wet cloth and the printing is continued.

2. Blisters

(1) Form: There are regular, different-colored dots such as sand. Contrary to the morphology of the scorpion.
(2) Cause:
1 The screen is not cleaned before the photosensitive coating is applied, and it is stained with dirt, which affects the normal light sensitivity of the photosensitive adhesive.
2 There are stains on non-patterned parts in black and white drafts.
3 The sensor has bubbles or improperly applied air bubbles.
4 When exposed to light, the exposure is insufficient or the photopolymer is not cured sufficiently, or the flashing is excessive, and the non-patterned photo resist is damaged.
(3) Preventive measures:
1 Strictly implement the technical requirements of each plate making process. When examining and proofreading, it must be comprehensive and careful. Repairs should be serious and thorough.
2 During the printing process, it is necessary to intensify the inspection of the fabric surface, to find the trachoma, and to repair it in time.

3. Leakage

(1) Morphology: regular, irregularly colored stripes, patches, or stains appear at regular intervals on the surface of the fabric. This is a common occurrence in production.
(2) Cause:
1 The emulsion is peeled off.
2 The plate was not repaired after the plate was made.
3 Flower damage creates holes.
4 Welt is not firm.
(3) Preventive measures:
1 When making the plate, clean the screen and put on the photopolymer. The photopolymer should be cured sufficiently.
2 Carefully and comprehensively when editing.
3 Stick firmly after stretching.
4 Intensify inspection during production, and repair in time when gliding occurs.

4. Wraps and whitening


(1) Form: Flowers are not allowed, and flower patterns are off-frame, that is, arbitrage. The flower-flower connection shows an undesired white background, that is, there is dew (2).
1 When the screen has stretched or stretched the tension is not uniform.
2 The black and white drafting performance is not uniform or it is not calibrated according to the standard line.
3 The color reproduction at the black and white manuscript is too narrow.
4 The instrument was not calibrated properly, resulting in inertial casing.
5 Gray cloth is too bulky.
6 The silk is not firm, and the fabric moves with the squeegee during printing.
7 When printing on the manual platen, the standard eye of the flower plate is inaccurate or slipped out of the standard eye, or the temperature of the platen is so high that the printing place is wrinkled, or the table plate is worn with regular eyes.
(3) Preventive measures:
1 Choose a screen frame with a stable shape, not easily deformed, strong applicability, moderate elasticity, and a screen as a stretch material.
2 The same lot number should be used for a set of film-drawing films, and the film should be cut in the same direction. The standard lines should be aligned. The black and white manuscripts shall be printed at the printing department, and the complex colors should be appropriate and not too narrow.
3 In the same kind of printing equipment, choose the equipment with high precision.
4 For fabrics with high hygroscopicity, they can be printed before moisture and then printed to ensure that the fabric is firm. When nylon fabrics are printed, they should be pre-formed before printing to stabilize the fabric and prevent moisture deformation.
5 Strengthen belt cleaning to remove surface impurities. If the paste fails, wash with acetone or reapply the paste.
6 When printing on the manual platen, it is necessary to calibrate the flower position of the flower plate before printing, and it is found that the rules and regulations of the table plate are worn out and they need to be replaced in time.

5. More flowers and more leaks

(1) Form: Patterns that do not exactly correspond to the spirit of the original appear on the surface of the fabric. More than the pattern of the original is more than one pattern, and less than the original pattern is the pattern of the missing flower.
(2) Cause:
1 The black and white manuscript described does not conform to the original manuscript. The omission of the inspection was not corrected.
2 When the plate was applied to the plate, the pattern was painted off.
(3) Preventive measures: Full proofreading, careful amendments, hard-to-revise, drafting or plate making.

6. Overlay printing

(1) Form: The patterns at the patchwork are overlapped, showing traces of patchwork.
(2) Cause:
1 When the open circuit is improper or the blank space and geometric pattern are connected, there is too much overlap to avoid whitening.
2 wire mesh expansion.
3 Wear eye or impact block.
(3) Preventive measures:
1 Open the right way.
2 After photographic exposure, carefully proofread and correct the overlaid portion to a minimum.
3 When stretching the net, the screen should be tensioned and the tension should be uniform. As far as possible, no nylon net with easy deformation should be used, and a small stretchable polyester screen should be used.
4 Correct rules eyes and crash blocks.