Continuous Ink Jet Printer (CIJ)
A Continuous Ink Jet Printer (CIJ) is a software-controlled, non-contact inkjet marking system. It applies pressure to the ink inside the system either by controlling an internal gear pump or through compressed gas supplied externally. This pressure forces the ink through a nozzle with a diameter of several micrometers. A crystal oscillation signal applied above the nozzle splits the continuous ink stream into droplets of equal size and spacing at a consistent frequency. As the droplets pass through a charging electrode, they are individually charged under control of the central processing unit (CPU). The actual charge and phase of each droplet are then verified by a detection electrode. Finally, the charged droplets are deflected by an electric field created by deflection electrodes, projecting them from the print head onto different positions on the product surface to form the desired text or patterns. Droplets that are not charged are collected in a recycling tank and re-enter the printer's ink circulation system.
Since the ink jetting is continuous, CIJ printers can use many types of inks, especially those that dry very quickly (within one second). Therefore, CIJ technology is ideal for products with non-porous surfaces that require immediate handling after printing, such as cans and plastics. Additionally, more vivid pigment-based inks can be used.
Due to the relatively high jetting speed of CIJ systems, the printing distance of CIJ is much greater than that of drop-on-demand (DOD) systems (generally over 10mm), without any loss in print quality. This allows for greater flexibility in placing the print head.
Most industrial inkjet systems use CIJ technology. Industrial CIJ printing systems can reach speeds of up to 1000 feet per minute, much faster than DOD systems, but the image quality is lower compared to DOD systems. CIJ is the best solution for large-scale direct mail order operations, numbering and marking of packaging printed products in the food, beverage, pharmaceutical, and cosmetics industries. It is also used for marking and coding lottery tickets.
Drop-on-Demand (DOD) Inkjet Printers
Industrial drop-on-demand systems consist of multiple high-precision valves. During printing, the corresponding valves open and close rapidly to allow ink, which is maintained under constant internal pressure, to be ejected onto moving surfaces to form characters or graphics. A digital signal produces a single ink droplet on paper rather than a continuous ink stream. The latest DOD print heads produce colors on paper using more precise dot matrices, resembling traditional offset printing. Therefore, in four-color high-precision printing where quality is the most important factor, DOD is the ideal choice, capable of producing near-photographic quality results. The printing speed of DOD ranges between 100 to 300 feet per minute. DOD applications include wide-format printing, colored icons on packaging, point-of-sale displays, textiles, and large format signage. However, in the industrial packaging industry, due to speed limitations, it cannot be applied on high-speed packaging lines. Many companies are developing high-speed DOD printing equipment suitable for packaging purposes, with nearly a dozen brands available just in Europe.
Drop-on-Demand (DOD) Inkjet Technology
DOD printers based on this principle are divided into three types: Piezoelectric Inkjet Technology, Valve-based Inkjet Technology, and Thermal Bubble Inkjet Technology.
1. Piezoelectric Inkjet Technology: Piezoelectric inkjet printers are also called high-resolution inkjet printers. Integrated print heads have 128 or more piezoelectric ceramic crystals controlling the nozzles. After CPU processing, a series of electrical signals are sent via a drive board to each piezoelectric crystal, causing deformation. This forces ink out of the nozzle onto the moving item’s surface, forming dots that create text, numbers, or graphics. Then, the piezoelectric crystal returns to its original shape, allowing new ink to enter the nozzle. Due to the high density of ink dots per square centimeter, piezoelectric technology can print high-quality text, complex logos, and barcodes.
2. Valve-based Inkjet Technology: Also known as Large Character Inkjet Printers, these have print heads consisting of 7 or 16 groups of high-precision intelligent micro-valves. During printing, the characters or graphics to be printed are processed by the computer motherboard and sent as a series of electrical signals to the intelligent micro-electromagnetic valves, which activate rapidly. The ink, maintained under constant internal pressure, forms droplets that are ejected onto the moving surface to create characters or graphics.