Pad printing process flow and process abnormality analysis

Pad printing is a supplementary expansion method of screen printing. It refers to the use of copper or steel gravure plates to cast a hemispherical pad printing head through silicone rubber, which is pressed against the layout to transfer the ink to the substrate to complete transfer printing. Way.The substrate is an irregular shaped surface (such as instruments, electrical parts, toys, etc.).

1) Typical products: used for surface printing of vehicle interiors, electronic consumer products and sports equipment.
(2) Suitable output: from single piece to large batch.
(3) Quality: Able to achieve clear printing details, even on uneven surfaces.
(4) Speed: single printing time (1-5 seconds).
2. Advantages:
(1) Wide range of applications: Pad printing is generally used on workpieces that cannot be processed by silk screen printing such as grooves and the back of the workpiece. Because there is no mesh limit for screen printing, the accuracy of pad printing patterns is relatively high. Since the pad printing machine is automatic The equipment has high precision, so it can perform color printing. Theoretically, the number of colors can be unlimited, but in actual operation, it will not exceed 7 colors.
(2) Easy to operate: the equipment operates fully automatically.
(3) Low cost: Except that the equipment is much more expensive than the screen printing machine, other cost factors are the same as those of the screen printing machine.
3. Disadvantages:
(1) Average effect: The visual effect of the finished product is slightly smoother than that of silk screen printing, but not far behind.
(2) Area limitation: Since the silicone pad printing head relies on elasticity and has an upper limit on the production size, pad printing cannot produce patterns that are too large.
(3) Color gradation limitation: Although pad printing can be used for color registration, it is still impossible to produce gradient colors due to the clear edges of the grooves processed by corrosion of the steel plate.
(4) Construction taboos: When using UV ink for construction, you need to use a darkroom or pay attention to shading to prevent the UV ink from curing and damaging the pad printing die and steel plate.
4. Pad printing process:
The steel plates are all coated with ink;
The pad printing machine starts up;
The silicone pad printing head is lowered to the steel plate;
Stick the ink on the character pattern to the silicone pad printing head;
The pad print head moves above the substrate and descends, and the ink on the surface of the silicone pad print head is transferred to the surface of the substrate;
Repeat the above operation.
Water transfer printing process:
Transfer batch film → Activation (use special solvent to activate the pattern on the film into ink state) → Transfer (use water pressure to transfer the pattern to the printed object) → Wash (rinse the remaining film with water) →Dry (dry the printed material) →Spray topcoat (spray PU transparent paint to protect the surface)

5. Process anomalies and analysis
(1) Phenomenon: bubbles or sand holes
Original solid: The pad printing rubber head is too soft, the rubber head is too flat and difficult to vent, and the surface of the rubber head is damaged; the steel plate is not etched in place; the ink is too thick or dries too fast; there is dust or oil on the surface of the product; the ink is deteriorated or expired.Solution: Replace a suitable rubber head; redo the pad printing steel plate; add corresponding additives; clean the surface with alcohol; replace with new ink.
(2) Phenomenon: The pattern is blurred and solid: the pad printing rubber head is too soft; the clamp is loose; the rubber head falls too fast; the steel plate is etched too deeply; the ink is too thin or too thick; there is dust or oil on the surface of the product.Solution: Replace the rubber head with suitable hardness; check whether the clamp that fixes the product is loose; adjust the descending speed of the rubber head; replace the steel plate with a moderate depth; use additives to adjust the consistency.
(3) Phenomenon: The rubber head does not stick to the original ink: there is oil on the surface of the rubber head; the ink concentration is too high and thick; the ink dries too fast; the etching pattern is too shallow, or the printing plate is defective; the angle of the rubber head is too large; the pattern If the color block is large, the scraper will scrape away the ink in the middle of the pattern; the ink taking pressure is too high.Solution: Use alcohol tape to clean it; add an appropriate amount of diluent; use slow-drying diluent; replace the printing plate; use a rubber head with a slightly flat angle; increase dots or use thick steel plates; reduce the ink pressure.
(4) Phenomenon: Ink drawing is original: the ink viscosity is too large; the rubber head rises too fast; the surface of the rubber head is damaged or deteriorates after being used for too long.Solution: Adjust the most suitable viscosity or consistency of the ink; adjust the rising speed; replace the rubber head; add filler to the ink to improve the drawing condition.