We would like to share the silk screen processing quality description and conventional testing methods today. Due to different enterprise standards, this article is only for reference, welcome to discuss together:
一. Screen printing inspection environment
- Luminosity :200-300LX (equivalent to 40W fluorescent lamp distance of 750MM)
2. The surface of the product to be inspected is approximately 45° from the visual direction of the inspector (as shown below), and the time is about 10 seconds.
3. The distance between the inspector’s visual direction and the surface of the product to be tested is as follows:
- Class A surface (the external surface that can be directly faced):400MM
- Grade B surface (not obvious outside):500MM
- Grade C surfaces (internal and external surfaces that are not easily visible):800MM
二. Common defects of silk screen printing
1.Foreign matter: After silk screen printing, dust, dot-like, or thread-like foreign matter is attached to the coating film.
2. Exposed bottom: due to the silk screen printing position being too thin to reveal the bottom color
3. Missing print: The required silk screen position has not been silk-screened.
4. Fuzzy/broken lines; Poor silk screen printing results in the uneven thickness of silk screen lines and patterns, blurring, and partially disconnected word lines.
5. Uneven thickness of silk screen printing: due to improper operation of silk screen printing, the thickness of the silk screen printing layer of dots, lines, or patterns is uneven.
6. Dislocation: Due to the inaccurate position of the silkscreen, the position of the silk screen is offset.
7. Poor adhesion: The adhesion of the silk screen coating is not enough, and it can be pasted off with 3M adhesive tape.
8. Pinholes: Pinholes can be seen on the surface of the coating film.
9. Scratches/Scratches: Caused by poor protection after silk screen printing
10. Mottled/Stained: Non-screened color adheres to the screened side.
11. Color difference: the color deviation compared with the standard color plate.
三. Screen printing reliability Inspection method
We provide the following 15 testing methods, each brand can test according to their own business needs.
1.High-temperature storage test
Storage temperature: +66°C
Storage time: 48 hours
Acceptance criteria: After the sample is out of the oven and placed at room temperature for 2 hours, the printed surface has no wrinkles, blisters, cracks, peeling, and no obvious change in color gloss
2. Low-temperature test
Storage temperature: -40°C
Storage time: 48 hours
Acceptance criteria: After the sample is out of the oven and placed at room temperature for 2 hours, the printed surface has no wrinkles, blisters, cracks, or peeling, and no obvious change in color glossy.
3.High temperature and high humidity storage test
Storage temperature/humidity: +66°C/85%
Storage time: 96 hours
Acceptance criteria: After the sample is out of the oven and placed at room temperature for 2 hours, the printed surface has no wrinkles, blisters, cracks, or peeling, and no obvious change in color gloss.
4.Thermal Shock Test
Storage temperature: -40°C/+66°C
Cycle Description: -40°C~+66°C is a cycle, and the conversion time between temperatures does not exceed 5 minutes, a total of 12 cycles
Acceptance criteria: after the sample is out of the oven and placed at room temperature for 2 hours, check that the parts and the printed surface are free from wrinkles, blisters, cracks, and peeling and that no obvious change in color gloss.
5.Silk/Pad Printing Adhesion Test
Purpose of the test: To evaluate the adhesion of silk/pad printing paint
Test tool: 1.3M600 scotch tape or scotch tape with a viscosity greater than 5.3N/18mm
Test method: Paste 3M600 transparent tape on the printed font or pattern of the sample to be tested and flatten it by hand, then pull up the tail of the tape at 90 degrees to the test surface, quickly tear off the same part of the tape and repeat 3 times.
Acceptance criteria: Observe the surface with the naked eye, the silk/pad printing fonts or patterns should be clearly discernible, and there is no peeling off.
6.Friction test
Purpose of the test: To evaluate the adhesion of painted surfaces and silk/pad printing paints.
Test Equipment: Eraser
Test method: Fix the test piece, rub it back and forth with a vertical force of 500G and a stroke of 15MM, and every single stroke is one stroke. Silk/pad printing fonts or patterns, continuous friction 50 times.
Acceptance criteria: Observe the surface with the naked eye, the wear cannot be seen at the bottom, and the silk/pad printing should be clearly distinguishable
7.Anti-solvent test
(1) Isopropanol test
Take 1 ml of isopropanol solution and drop it on the sprayed surface of the sample or silk/pad printing surface. After 10 minutes, dry the isopropanol solution with a white cloth
(2) Anti-alcohol test
Test method: Soak a cotton ball or white cloth with a 99% alcohol solution, and then wipe back and forth 20 times at the same position of the printed font and pattern of the sample with a pressure of 1kg and a speed of 1 reciprocation per second.
Acceptance criteria: After the surface of the sample is wiped, the printed characters or patterns should be clearly visible, and the color should not lose light or fade.
8.Thumb test
Conditions: 5PCS or more of experimental samples
Experimental procedure: Take a sample, put your thumb on the printed picture, and wipe it back and forth for 15 times with a force of 3+0.5/-0KGF.
Experimental judgment: the printed pattern of the product must not have gaps/broken lines/poor ink adhesion, etc., otherwise it is unqualified.
9.75% alcohol test
Conditions: more than 5PCS of experimental samples, white cotton gauze, 75% alcohol, 1.5+0.5/-0KGF
Experimental procedure: tie the bottom of the 1.5KGF tool with white cotton gauze, dip it in 75% alcohol, and then use the white cotton gauze to go back and forth on the printed pattern 30 times (about 15SEC)
Experimental judgment: the printed pattern of the product must not have falling off/broken lines/poor ink adhesion, etc., and the color is allowed to be light, but the printed pattern should be clear and not blurred, otherwise it is unqualified.
10.95% alcohol test
Conditions: more than 5PCS of experimental samples, white cotton gauze, 95% alcohol, 1.5+0.5/-0KGF
Experimental procedure: tie the bottom of the 1.5KGF tool with white cotton gauze, dip it in 95% alcohol, and then use the white cotton gauze to go back and forth on the printed pattern 30 times (about 15SEC)
Experimental judgment: the printed pattern of the product must not have falling off/broken lines/poor ink adhesion, etc., and the color is allowed to be light, but the printed pattern should be clear and not blurred, otherwise it is unqualified.
11.810 tape test
Conditions: Test samples above 5PCS, 810 adhesive tape
Experimental procedure: Paste the 810 adhesive tape completely on the screen printing, then quickly pull up the adhesive tape at an angle of 45 degrees, and measure three times in a row.
Experimental judgment: the printed pattern of the product must not have gaps/broken lines.
12.3M600 tape test
Conditions: more than 5PCS of experimental samples, 600 adhesive tapes
Experimental procedure: Paste the 3M600 tape completely on the screen printing, and quickly pull up the tape at a 45-degree angle. Just test it once.
Experimental judgment: the printed pattern of the product must not have gaps/broken lines.
13.250 tape test
Conditions: more than 5PCS of experimental samples, 250 adhesive tapes
Experimental procedure: Paste 250 pieces of tape completely on the screen printing, quickly pull up the tape at an angle of 45 degrees, and do it three times in a row.
Experimental judgment: the printed pattern of the product must not have gaps/broken lines.
14.Gasoline Wipe Test
Conditions: more than 5PCS of experimental samples, white cotton gauze, gasoline mixture (gasoline: 75% alcohol = 1:1), 1.5+0.5/-0KGF
Experimental procedure: tie the bottom of the 1.5KGF tool with white cotton gauze, dip it in gasoline mixture, and go back and forth on the printed pattern 30 times (about 15 SEC)
Experimental judgment: the printed pattern of the product must not have falling off/notches/broken lines/poor ink adhesion, etc., and the color is allowed to be lighter, but the printed pattern should be clear and not blurred, otherwise it is unqualified.
15.n-Hexane Wipe Test
Conditions: more than 5PCS of experimental samples, white cotton gauze, n-hexane, 1.5+0.5/-0KGF
Experimental procedure: tie the bottom of the 1.5KGF tool with white cotton gauze, dip it in n-hexane solution, and go back and forth on the printed pattern 30 times (about 15 SEC)
Experimental judgment: the printed pattern of the product must not have falling off/notches/broken lines/poor ink adhesion, etc., and the color is allowed to be lighter, but the printed pattern should be clear and not blurred, otherwise it is unqualified.
