The process of using electric pad printing machine
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1 Composition of electric pad printing machine
The main components of the electric pad printing machine are: rubber head, oil pan, scraper set, stepless speed governor, switch (run/manual), jig lift table, etc. Because it does not need the traditional air pump air source, and adopts the mechanical transmission system of 220V power supply and electronic stepless speed change, the equipment has good stability, controllable precision, low cost, small size, convenient use and reliable quality.
2 model of the plastic head
The rubber head should have good ink absorption and deinking properties, good resilience, fatigue resistance, solvent resistance and other properties. The size, shape, hardness and hardness of the plastic head should be selected according to the chart or physical model provided by the supplier, and then a model specification is determined according to the actual use and life.
The contact deformation between the rubber head and the substrate should be as small as possible, and its diameter is about 3 mm larger than the word. If the printing plate has many thin lines, the plastic head should be relatively soft. The extrusion depth of the plastic head and the substrate shall not exceed 1/3 of the height of the plastic head, otherwise the rubber head may be easily damaged and the ink case deformation is blurred. The newly purchased plastic head has a layer of release agent on the surface, which is cleaned with a clean cloth, ethanol or a washing agent before use.
3 type of ink
Common inks are often used. This type of ink and additives can print character patterns on pigmented rubber, metallic glass, nylon canvas and other materials. It is characterized by low cost, strong adhesion and ideal color. However, it is not applicable to PE/PP, baking ceramics, etc., and the corresponding thinner should be selected according to the pattern text, the size of the area and the adaptability of the substrate. Generally, the standard type is used.
4 fixture design
According to the shape of the substrate, a special fixture should be designed and manufactured to firmly hold the substrate, ensure the printing accuracy and repeatability in the printing process, and the convenience and simplicity of the pick-and-place operation. For a large number of prints, a conveyor belt structure can be designed for efficiency.
5 scraper
The quality evaluation indexes of the scraper mainly include hardness, thickness, elasticity, and straightness of the knife edge.
Generally, a straight steel strip with a good elasticity of 0.25 mm is used as a scraper. The cutting edge should be sharp, smooth and straight, and it can closely match the steel plate. If the blade edge is not sharp or defective, it will cause the ink to be clean and adhere to the edge of the image or cause the ink mark of the blade. The serious plate is scratched. When using, the scraper should be at an angle to the printing plate to prevent the squeegee from falling into the concave portion of the printing plate, and excessively squeegee damages the graphic. The length of the scraper should be greater than the width of the pattern text near the steel plate. The pressure of the scraper should be as small as possible on the premise of scraping the ink on the non-image part of the plate.
6 Early warning and countermeasures
1) Control of art conditions
·Printer operation
You should be familiar with the working conditions of each stage of the main organization and the operations that can be selected in turn. After the small test is normal, in principle, only the printing surface, buttons and display lights are used.
·Printing plate installation
The printing plate is fixed in the middle of the ink tray, and then the fixture of the substrate is adjusted so that the plastic head is aligned with the center of the printing plate and aligned with the printing center of the printing substrate, and the printing plate installation is completed.
·Adjustment of plastic head, control speed
In the pad printing operation, the falling and lifting of the plastic head determines the transfer rate of the ink to some extent, which affects the forming of the image. Therefore, under the premise that the rubber head, the substrate, the ink flow and the like are adjusted in place, appropriately slowing down the machine speed is conducive to improving the quality of the printed product.
· Add solvent to control ink flow
According to the amount of printing, the ink solvent is prepared at one time. Generally, the ratio of ink to solvent is 1:2 (winter spring and autumn)~2:5 (summer). That is, use a slow release agent when it is too hot or quick-drying; instead, use a quick-drying agent if it is too cold or slow to dry. At regular intervals, a certain amount of the diluted ink is added in advance according to the amount of ink used in the substrate.
·Control of wet temperature
The essence is to make the solvent in the ink have a relatively stable volatilization speed. An easy way to control temperature and humidity is to print in an air-conditioned workshop.
2) Problems and suggestions
· Graphic distortion
It is mainly caused by the deviation of the load, hardness, radius of curvature of the surface and the thickness, size, depth and relative position of the transfer. Choose more types of rubber heads, or use the normal steel plate and queue fault source to select the correct process.
·Return ink color, open field
Mainly due to improper ink selection and use, the ink should not be too thin to have a thick color paste to join.
·Blotting edge
Check if the scraper is sharp or notched, whether the ink is too thin, whether the rubber head or steel plate is worn or not.