The reason why pad printing is used for lens printing is that pad printing can print on a smooth and curved surface, and laser marking will cause damage to the lens surface. In addition to pad printing, the frame printing can also be done by laser marking. Both pad printing and laser marking can achieve decoration on a very small area, but they have obvious differences: laser marking actually has an etching effect and can be stored forever: pad printing pictures and texts are easy to peel off, but you can choose whatever you want Color to increase the eye-catching effect.
Control of pad printing elements
The most significant feature of pad printing is indirect printing. The biggest advantage of indirect printing is to maintain the independence of the printing plate and the substrate. The change in the shape of the pad printing rubber head that transfers the ink on the printing plate to the surface of the substrate makes the shift The adaptability of printing technology to the shape of the substrate is greatly enhanced.
The following is an introduction to the process issues involved in the printing of pad printing technology on glasses:
1. Ink selection
Ink selection occupies a very important position in pad printing technology, which is related to the wide range of printing materials involved in pad printing technology. Since the frame is made of metal, the ink is required to have good adhesion on the metal surface. Now, two-component inks are commonly used, and they are dried by drying. The printing of lenses requires glass ink, which is usually a two-component ink and is dried by drying. The cured ink layer of the two-component ink has the characteristics of high hardness and good adhesion, but the operation is slightly more troublesome.
The use of two-component ink is briefly described as follows:
(1) First add the hardener to the ink according to the instructions of the ink, stir it evenly, and pour it into the oil pan for printing. Since the two-component ink will cure slowly, the dosage should be controlled.
(2) After printing, it should be placed in a drying box for drying treatment to speed up the drying speed. Two-component inks generally have a drying time of up to 10 hours at room temperature, which will affect production efficiency. Drying is ideal. Usually the drying temperature is between 150°C and 180°C, and the time is 5 minutes to 10 minutes. minute.
2. Pad printing plastic head
The choice of the pad printing rubber head in the pad printing process is very important. First of all, the shape of the pad printing rubber head must be able to print to the specified position, and secondly, ensure that the deformation is small. Since the printing area of the frame is very small, the pad printing rubber head should be slightly pointed. Through the test, the A7 rubber head with a cross-sectional area of 38mm is more suitable. The printing effect of the A3 plastic head is also very good, but because the cross section is slightly smaller, the printing distortion is slightly larger.
The hardness of the pad printing rubber head is another indicator that should be considered when choosing. The softer rubber head has a wider adaptability, but the printing image and text are deformed. Especially for printed products as small as glasses frames, the graphic text is very small, and the large deformation of the graphic can easily cause the adhesion between the graphic lines and the blur, so it is better to choose a harder plastic head. Our test The result is that the plastic head with a Shore hardness of 32 degrees can achieve the best printing quality.
The rubber head selected for the printing of the nose pad should be selected with a smaller cross-sectional area in consideration of location limitations. Our test results are that the rubber head with a cross-sectional area below 15mm is more suitable, and the hardness should also be above 32 degrees.
3. Steel plate
The printing plate of the pad printer is a steel plate, and the method of making the steel plate is the corrosion method. The printing pictures of the frame and the lens are very small.