The pad printing pad is the iconic part of the pad printing machine, how to choose the pad printing pad is the most important part of the pad printing process.
The raw material of pad printing head is silicone rubber. Silicone rubber is vulcanized in different proportions with silicone oil and poured into molds of different shapes to make rubber heads of various shapes. Usually, the shape of the rubber head needs to be selected according to the shape of the printed image and necessary tests.
Polished aluminum or crystal glue is used as the mold when making the rubber head. The hardness of the pad printing rubber head is determined by the silica gel and silicone oil prepared according to different proportions. After 24 hours or longer vulcanization time, the pad printing rubber head It took shape.
The glue head is generally shaped with wood or aluminum. Wooden board and aluminum board are also fixed boards installed on the pad printing machine. The shape of the glue head has a common feature: the central area is raised, and the surrounding area is slowly descending, similar to a hillside. This structure is conducive to the transfer of ink and the discharge of air from the central area.
The ideal shape is a hemisphere. When the round rubber head is squeezed, the force on the side is balanced, and it is impossible to leave air bubbles between the rubber head and the ink during printing. By squeezing, the glue tip does a good job of picking up ink from the plate and transferring it to the substrate.
The cross-sectional area of the rubber head is similar to a square, but it will gradually rise in the center of the rectangle. For some square patterns, the square rubber head should be preferred. The center point of the square rubber head must also be in a raised shape, which is also conducive to the extrusion effect of exhaust.
3. Long strip
For some slender products, the strip-shaped rubber head should be considered. It is squeezed more in the length direction than in the width direction, but the deformation is small. It is often used to print egg packaging boxes, rulers and remote controls. Due to the different pressures on the length and width of such products, the necessary cutting can sometimes be performed.
4. Special shape
If the pattern is not concentrated enough, there is a raised part in the middle of the printed pattern of the product, the edge of the dial, and the product of the step shape, it may be necessary to make a special shape of the rubber head. The special shape of the rubber head may be different due to the different pressure on each part. If the deformation of the pattern is uneven, necessary corrections should be made. How to make the product pad printing in the best state is the most important criterion for selecting the rubber head.
The cross-sectional size of the pad printing head should be larger than the pattern to be printed, so that the deformation of the pad printing head will be smaller, and the smaller the deformation, the deformation of the pattern will be the smallest. Sometimes, you need to change the contact angle between the pad and the product Only then will a very ideal imprint be obtained.
The hardness of the rubber head is measured by the Shore durometer. The larger the degree, the greater the hardness, the smaller the deformation during pad printing, and the higher the precision. The hardness of the rubber head depends on the ratio of silicone rubber and silicone oil when making the rubber head, and the proportion of silicone oil The higher the rubber head, the softer it is. When printing more curved substrates, soft rubber heads should be used, and for relatively flat products, choose pad printing rubber heads with higher hardness.
Complete solidification requires 2-5 hours. Adjust the percentage of silicon oil can adjust the the hardness of rubber pad. Less percentage of silicon oil will produce a harder pad. When you increase the percentage of silicon pad, please add corresponding percentage of hardener. But, too much percentage of silicon oil will affect pad quality negatively. Precision hardness of rubber pad need measure with Shore durometer.