Discussion on Principle of Pad Printing and Adaptability of Ink

A: Pad printing is a printing technology that transfers the pattern on the steel plate to the object through the concave plastic head as an intermediate.

B: When printing, the depth of the steel plate, the hardness of the glue head, the size, shape, characteristics of the ink, the volatilization speed, the surface characteristics of the printed object (smooth or rough, the size of the arc, etc.), the control of the working environment (such as temperature, Color, humidity, dustproof, etc.). The changes of the above-mentioned related parameters must be dealt with and adjusted to be successfully transferred.

C: Whether the depth of the steel plate is appropriate. 1. Measured with a depth gauge, the depth of conventional pad printing steel plate is about 2.4 microns. For small text, the line is 2 microns. For solid graphics, less than 3 microns is also suitable, and the dots of 1.6 microns may be too deep. The difference between the specific steel plate depth. 2. The actual use depends on the requirements of the pattern and the ink layer. It is also like a picture and text. If the printing work surface is rough, pitted or smooth, the required steel plate depth has a printing effect. For example: if oil return occurs, the picture is blurred, the possibility is that the steel plate is too deep, and if air bubbles (trachoma) appear, it may be too shallow. If the printing head is not printed on the object, the ink on the head has been dried up, the steel plate is too light. If the ink on the glue head is uneven (orange peeling), the steel plate is too deep. Since the glue head can only pick up a small part of the ink in the pattern area of ​​the steel plate, there will be no benefit if the etching depth is too large. When the etching depth is 25 microns, the glue head can only pick up the ink film of 12 microns, and the rest is left on the steel plate. Since the ink film contains at least 40% of the thinner, this part of the thinner is completely evaporated in the ink transfer and drying, so the ink layer left on the printed object is about 7 microns.

D: Selection of glue head. 1. Flexible. 2. There are radians. 3. Not infinite. This means that pad printing cannot print large-area patterns, but it is very suitable for irregular shapes and uneven workpiece printing. At present, the diversification of the color of the plastic head (red, white, yellow, blue) is mainly determined by the color of the raw material of the plastic head. From the point of view of the printing head, the color does not affect the transfer of the head (whether the ink is soaked and deinked completely), and the material and process of the head are the most important.

More than 100 plastic heads made by KAIYI are all made with crystal molds and vacuum exhaust. Not only the appearance is smooth and smooth, but even the fine lines and text can be clearly transferred. And there are no bubbles in the plastic head, trachoma, more durable. The hardness of the glue head affects the quality of the print pattern and the durability of the glue head itself. The hard plastic head can transfer the pattern very well and has good durability. However, when the printed object has a large arc, a soft plastic head is used because it is easier to touch the various parts of the arc. In this way, the smaller the deformation of the plastic head, the more accurate and clear the printed pattern. The ink sticking effect of the new plastic head is not ideal. It can be solved by first printing multiple times or wiping the surface with alcohol or neutral solvent. Wipe with a strong solvent such as ink thinner, although the glue head will soon be inked, but the effect of transferring the pattern will be poor, and accelerate the aging of the glue head. The print quality of the glue head will gradually decline, because the silicone oil is slowly scrubbed off, so the surface will become rough and absorbent.

E: Ink characteristics: Pad printing requires quick drying with oil and water to avoid the ink head from transferring ink well. Screen printing requires slow drying to avoid blocking the screen. This is also the difference between screen printing and pad printing thinner. However, under certain conditions (such as drying and high temperature), silk screen printing oil can be used for pad printing.

Single-component ink, the durability of the plastic head is better. The two-component ink is usually corrosive and easy to foam, which will make the silicone oil of the glue head consume faster, so the service life of the glue head will be shortened. When the glue head is not printed on the object, and the ink on the glue head is dry, the thinner dries too quickly. When the printing is completed, the pictures and text on the printed matter appear fluffing and drawing, and they dry too quickly. Oil return is fuzzy; it is too slow to dry, and it has broken into pieces, it has no adhesion, and it is too fast to dry;

F: Why the phenomenon of air bubbles (trachoma) often occurs in printing. Mainly focus on three aspects of plastic head, steel plate and ink. 1. The shape of the plastic head is not suitable, too flat or the curvature is wrong. 2. The center point (highest point) of the plastic head is printed on the pattern, forming air that cannot be discharged and generating bubbles. 3. The aging of the glue head is sticky and damaged, and the oil head causes poor printing of the glue head. 4. Steel plate etching, the oil layer is not thick enough. 6. The ink is too thin or too slow to dry. 7. The ink is too dry or too fast.

G: Working environment for pad printing: room turbidity (optimally 18-20 ° C). Humidity is (optimally 60% -070%). dust-proof. Light white wall etc. For beginners, we can start with monochrome machines, small patterns, and round plastic heads with pointed tips. Choose easy-to-print materials such as PVC and PS. Introduction to light or white background, when the effect is not ideal, it can be improved by adjusting or replacing the plastic head, steel plate or ink separately.

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