Working Principle of Coding Machines

A coding machine is a device that uses software control and non-contact method to mark products. According to the difference in working principles, coding machines can be divided into three categories: continuous inkjet printers, drop-on-demand printers, and laser coders. A coding machine is a device that uses software control and non-contact method to mark products. From the consumables used by coding machines: one type is ink-based coding machines; another type is non-ink coding machines (laser coders); from the working form: one type is inline coding machines, mainly used for assembly lines; another type is mobile coding machines, where the object is stationary and the coder moves, similar to handheld coders on the market. Currently, the Chinese market includes imported machines, domestic machines, and joint venture machines. In recent years, domestic coding machines have grown strongly, and some performances have matched or even exceeded imported ones. Coding machines are widely accepted by users due to their wide range of applications and strong adaptability. In the figure below, the left is a mobile coder (handheld coder), and the right is an inline coder.

Working Principle of Coding Machine:

(1) Continuous Inkjet Technology (Continuous Inkjet Printer) Working Principle: Under pressure, ink enters the print head, which contains a piezoelectric vibrator. Through vibration, the ink forms fixed-interval dots after being ejected. Through CPU processing and phase tracking, some ink droplets are charged with different charges by the charging electrode. After passing through a high-voltage magnetic field of several thousand volts, they deflect differently, fly out of the print head, and land on the moving product surface, forming a dot matrix, thereby forming text, numbers, or graphics. The remaining ink droplets are not charged and do not deflect; they directly shoot into the recovery tank for reuse. CIJ coding machine working principle diagram: Under the pressure of the ink supply pump, ink flows from the ink tank through the ink path pipeline, adjusts pressure and viscosity, enters the print head. As pressure continues, ink is ejected from the nozzle. When passing through the nozzle, the ink breaks into a continuous series of equally spaced and uniformly sized droplets due to the action of the piezoelectric crystal. The ejected ink stream continues downward and passes through the charging electrode to be charged. At the charging electrode, droplets separate from the ink stream. A certain voltage is applied to the charging electrode. When a droplet separates from the conductive ink stream, it instantly carries a negative charge proportional to the applied voltage. By changing the voltage frequency of the charging electrode to match the droplet breakup frequency, each droplet can be charged with a predetermined negative charge. Under continuous pressure, the ink stream continues downward, passing between two deflection plates with positive and negative voltages. Charged droplets deflect when passing through the deflection plates; the degree of deflection depends on the amount of charge. Uncharged droplets do not deflect and fly straight down into the recovery tube, eventually returning to the ink tank for recycling. Deflected droplets land at a certain speed and angle on objects passing in front of the vertical print head. The information to be printed is processed by the computer motherboard, changing the charge on the droplets to generate different identification information.

(2) Drop-on-Demand Technology (DOD) coding machines are divided into three types: piezoelectric inkjet technology, valve jet inkjet technology, and thermal inkjet technology. 1) Piezoelectric inkjet technology: Piezoelectric coders, also called high-resolution coders, have an integrated print head with 128 or more piezoelectric crystals controlling multiple nozzles on the nozzle plate. Through CPU processing, the driver board outputs a series of electrical signals to each piezoelectric crystal, causing deformation, so that ink is ejected from the nozzles, landing on the moving object surface, forming a dot matrix to create text, numbers, or graphics. Then, the piezoelectric crystals return to their original state, and new ink enters the nozzles due to surface tension. Because the dot density per square centimeter is very high, piezoelectric technology can print high-quality text, complex logos, barcodes, and other information. Electromagnetic valve type coder (large character coder): The print head consists of 7 or 16 sets of high-precision intelligent micro-valves. During printing, the characters or graphics to be printed are processed by the computer motherboard, and the output board outputs a series of electrical signals to the intelligent micro-solenoid valves. The valves open and close quickly, and ink is ejected as droplets under constant internal pressure, forming characters or graphics on the moving surface of the object being printed.

(3) Thermal Inkjet Technology: Thermal Inkjet Technology (TIJ) uses a thin-film resistor to heat less than 0.5% of the ink in the ink ejection area, forming a bubble. This bubble expands extremely quickly (less than 10 microseconds), forcing the ink droplet out of the nozzle. The bubble continues to grow for a few more microseconds and then collapses back onto the resistor. When the bubble collapses, the ink in the nozzle retracts. Then surface tension creates suction to pull new ink into the ejection area. Thermal inkjet printing technology is structured by such an integrated cyclic technical process.