Pad printing is to transfer the pattern LOGO trademark to the imitation of the product through the stamping method through the printing plate and the printing rubber head. Using the principle of imaging, the pattern to be printed is etched on the steel plate, and then printed on the flat screen The machine uses a soft rubber pad (silicone rubber head to transfer ink from the steel plate to the object to be printed. Pad printing can be suitable for printing of various workpieces, shapes, positions and high-speed printing, and the effect of the decorative pattern is better than Screen printing, oil injection, ironing, stickers and other methods are more detailed and beautiful.
2. Problems and solutions in the printing process of flat screen printing machine
1 The ink squeegee applies the ink to the etched recesses, and then the blade scrapes the ink on the steel plate back into the ink container on the return stroke. The etched ink left after evaporation can increase its surface viscosity.
2 The print head moves down to contact with the etching of printing.
3 When the print head rises, the ink in the etching will be sucked on the glue head.
4 During the process of moving to the printed part on the steel plate at the print head, the attached ink solvent gradually volatilizes, so that the viscosity of the ink increases again, and the print head will stay in the horizontal position above the printed matter.
5 The printing head presses down on the printing piece to transfer the attached ink to the surface of the printed matter.
6 The printing head rises again to return to the original position of the printing board.
3. Scope of application
Suitable for daily necessities, electrical products, optical products, plastics, toys, electronics, glass and metal industries.
Four. Flat screen printing machine
The flat screen printing machine is the core of pad printing production. It uses compressed air as the original power, and uses electrical signals to control the movement of the plastic head and pad printing actions (such as the number of prints) to print single-color or overprint two-color to multi-color patterns. Perform 1-3 times flow printing, 1-2 color turntable printing and 2-6 color push disk printing. (Note: The large pattern area needs to be printed in sections, but it is necessary to pay attention to the problem of misalignment.) According to the area and volume of the printed object, choose a flat screen printing machine, and choose monochrome, two-color or scroll printing according to the needs. Function, and select the dial and buttons according to the operating instructions of the k machine to determine the corresponding functions and set the process parameters.
5. Selection of steel plate, pad printing head and ink
(1) The choice of etching steel plate
1 The printed board includes steel plate, nylon board and quick printing board. Steel printing plates are the most durable and can be used almost indefinitely for long periods of time, while the service life of nylon plates and rapid printing plates can only be printed from 5,000 to 10,000 times, and the cost of steel plates is much higher than nylon plates and rapid printing plates.
2 The etching depth of the printed board is 0.015MM-0.035MM, the thickness of the printing ink film is 0.004-0.008MM, depending on the etching depth of the printing plate type and the hardness and shape of the print head, other such as temperature, humidity, and environment The thickness of the ink film may vary.
3 The size of the printed board is measured by the area of the printed pattern, usually the area of the printed board need not be too large, otherwise it is difficult to fix the steel plate on the oil pan. Therefore, steel plates of different sizes need to be matched with equivalent oil pans, blades and oil scrapers.
(2) The choice of printing glue
1 Hardness
Generally, printing pads can be divided into three kinds of hardness: soft S (30°A), medium M (35°A), and hard H (40°A). For finer printing patterns, harder printing pads can be used. If the printed parts are uneven, it is better to choose softer printing glue to reduce the loss. If the ink and thinner water have an erosive effect on the pad, you should choose an alternative ink or change the composition of the pad.
2 Volume
The size and size of the pad printing glue are better than that of the pattern, and it is best to be just enough. The volume of the glue head is too wasteful. Different types of pads need to use different types of pad printing glue.
3 Shape
The shape of the pad printing head needs to be adjusted according to the unevenness of the pad printing piece. If the surface of the piece to be printed is not flat, it is the key to choose the shape of the pad printing piece. Pad printing glue should bring the ink on the flat steel plate to the uneven printed piece, then the end of the pad printing glue should be very flexible, and the shape of the pad printing glue must be suitable for the width of the piece to be printed. Only the pressure can be spread evenly so as to avoid the printing paste obliquely printed on the plane of the printed object.
4 The glue head is made of three raw materials: rubber paste, silicone oil and drier.
(3) Selection of ink
1 Printed parts of different materials should use different series of inks.
2 Understand the gloss, hiding power and setting speed characteristics of ink.
3 Understand that ink and thinning water will not erode the pad printing head.
4 The speed of ink setting should not be too fast, otherwise it will be easy to dry in the oil pan, at this time, it can be diluted with thinner water. If you want to speed up the air drying speed, you can use quick drying agent or hair dryer to assist,
5 The ink should be adjusted to an appropriate viscosity. If the ink is too sticky, the lack of activity leads to difficulty in printing (easy to fluff); if the ink is too thin, the printed pattern color is not clear enough or the lines are not good; therefore, the ink blending is A major job. Pay attention to the viscosity of the ink on the steel plate. There are many types of inks, and it is necessary to use inks that match the characteristics to get the best results.
(4) Pad printing base
Do a good job of fixing the position on the printed workbench. The printed parts should be positioned accurately during printing and cannot be moved, and they can be easily taken in and out. Therefore, there must be a set of suitable fixtures for the printed parts. Determine manufacturing.
The bottom mold can be made of bakelite, bakelite, metal materials, plastics, gypsum, epoxy mud and other materials, with the principle of practicality, the form is eclectic.
(5) Dust is the biggest threat in the printing work, so dust prevention is also an extremely important task, so don't take it lightly.
