Screen printing quality inspection
A. Appearance inspection: (test method: visual inspection, hand feeling)
1. The color is in line with the sample (no obvious color difference under natural light or fluorescent light with normal eyesight), and there is no color difference in the same batch of products (Note: color difference includes color and glossiness);
2. the surface of the coating is smooth, flat, and uniform, and the surface shall not have the following defects.
a) Not dry and sticky: the surface is dry, but not dry, the surface has (or easy to produce) grain marks, sticky fabric lint phenomenon;
b) hanging: the surface of the liquid flow-like protrusion, the top is bead-shaped;
c) granular: the surface is gritty, with a sense of obstruction by hand;
d) orange peel: the appearance of the orange peel-like bumpy, irregular ripples;
e) Leakage bottom: the surface is transparent green, revealing the color of the substrate;
f) Pockmark: the surface shrinkage and present small holes (pockmark), also known as pinholes;
g) flowering: the surface color varies in shades and is patterned;
h) wrinkling: local accumulation of raised, wrinkled (except wrinkled powder);
i) inclusions: the coating with debris;
j) mechanical damage: external force caused by scratches, scratches, wear and tear, bruises.
Evaluation method: normal vision in natural light or fluorescent light from the product at 1M observation.
Judgment: visible defects are not acceptable defects, the parts or products for unqualified parts or unqualified products.
Second, the coating adhesion: (test method: Hundred Gram test)
A. Test method
Hundred grid test on the surface of the coating, the test method is as follows.
Use a sharp blade to cut 11 parallel straight lines with a spacing of 2㎜ in the longitudinal and transverse directions on the coating surface, forming 100 squares with a side length of 2㎜ (Note: ① the blade should be perpendicular to the scribed plane when scribing ② a ruler should be used when scribing ③ the scratches should penetrate the coating), use ordinary sealing tape to stick to the scribed area, compact and squeeze out the air, stop for 10 seconds, hold the end of the tape, and the surface of the workpiece under test is 45 ° Direction, the tape will be quickly pulled up, check the square coating stick off, damage;
B. Rating method.
Level 0: There should be no shedding phenomenon (including crossover);
Grade 1: less than 5% of the crossover;
Grade 2: crossings greater than 5% less than 15% off;
Level 3: crossings greater than 15% less than 25% of the shedding;
Level 4: crossings greater than 25% less than 35% off;
Grade 5: crossings greater than 35% of the shedding (including crossings);
1. When the thickness of the coating is less than 40μm, the edge length of the square is not more than 1㎜, and it is qualified for level 2;
2. When the coating thickness is greater than 40μm and less than 9 0μm, the length of the square is greater than 1mm and less than 2mm, and it is qualified at level 3;
3. When the thickness of the coating is more than 90μm and less than 12μm, the edge length of the square is 2mm, and it is qualified for grade 4;
4. When the coating thickness is more than 120μm, the adhesion will be reduced, and the general requirement is that the coating thickness does not exceed 120μm, and the judgment standard is tentatively set at this time: a complete square is not qualified.
Third, the coating resistance to alcohol melt: wipe with white cotton cloth jiao alcohol in the coating surface repeatedly (without strong pressure) 10 times, the cotton cloth should not be visible on the coating off phenomenon; to be completely evaporated alcohol, wiped parts and not wiped parts should be no color and gloss differences.
Fourth, acceptance requirements: to send the number (purchase batch) as the inspection batch, a full inspection of appearance, other inspection items following GB2828-1987 sampling inspection, using a normal inspection sampling program, the body requirements are as follows.
1, size and location: special inspection level (S-2); qualified quality level AQL = 4.0;
2, adhesion: special inspection level (S-1); qualified quality level AQL = 6.5;
3、Alcohol melt resistance: Special inspection level (S-3); Qualified quality level AQL=2.5.