Inkjet product printing and coding has come a long way in a relatively short amount of time. Many of the biggest innovations in industry materials have come within the last twenty years, allowing for the establishment of newer and improved technologies. In this article, we’ll look at the history of inkjet product printing and coding technology, from the invention of liquid jet printing devices in 1948 to the cutting-edge equipment and materials being used today.
One of the very first “liquid jet” printing devices was invented by Rune Elmqvist in 1948. It essentially worked by squeezing a continuous stream of liquid through a fine tube displaced by an electrified coil of wire. This invention differed from other liquid jet printers established during this time because the ink tube didn’t require contact with the recording surface. This meant the Elmqvist printer could work much faster than one that relied on direct ink writing due to the decreased amount of inertia and increased range of signals it could record. The Elmqvist liquid jet printing device is considered by many to be the forefather of inkjet printing and coding.
The next major advancement in inkjet technology arrived in the late 1960s with continuous inkjet (CIJ) printing. This technology uses a continuous stream of ink that’s broken up into individual charged droplets using an actuator, a device that converts electrical impulses into mechanical movements. The charged droplets are allowed to hit the print surface, while the uncharged and unwanted droplets are diverted into a collection device and recycled to be reused.
CIJ technology was an immediate success, and these printing systems are still some of the most commonly used in high-speed printing and coding operations today. The technology remains popular partially because its inks can use strong solvents like methyl ethyl ketone that dry very quickly. Continuous inkjet printers can also use low solid, food-safe inks, even in high-speed manufacturing lines, which is why they’re often used in the food industry for printing dates on perishable foods like eggs.
Soon after the invention of CIJ printing, researchers began developing printing technology that used electrical signals to eject ink only when necessary. This technology became known as drop-on-demand (DOD) inkjet printing. Drop-on-demand printing reduced the amount of ink that needed to be pressurized and recirculated, which also meant less solvent was needed to control ink viscosity. DOD ink compatibility is much broader than in CIJ technology, and printable materials can include electrical insulators.
The method used to achieve drop-on-demand inkjet varies, so DOD is an umbrella term for multiple printing and coding technologies. The three most common DOD printing technologies are valve jet, thermal inkjet, and piezoelectric inkjet. Below we’ll examine the histories and current applications of each of these printing technologies in more depth.
Piezoelectric inkjet (PIJ) printing was invented in the early 1970s. It improved upon CIJ technology by applying an electrical signal to the piezoelectric actuator (an electrically polarized ceramic device) only when a droplet of ink is needed. However, several of these actuators are needed to charge multiple droplets at the same time to form characters. Researchers took multiple approaches to solve this problem, including stacking flat-shaped actuators on top of each other, but ultimately the issue was resolved using an array of channels and chambers with piezoelectric crystals to force out the ink. This became the basis for our current piezoelectric printing technology.
PIJ technology allows for a wider variety of ink formulations than its main competitor, thermal inkjet, but the PIJ print heads are generally more expensive to manufacture and purchase. Piezoelectric printing technology is used extensively in current product marking and coding applications, especially when high-resolution printing is required.
Approximately a decade after the first PIJ systems were invented, Canon, a leading digital imaging company, developed a competing technology that was originally called BubbleJet but is now mostly known as thermal inkjet (TIJ). This technology worked by thermally increasing the pressure of ink near the ejection nozzles using electrical resistors. At the same time that Canon was developing the TIJ printing technology, the company also developed the ink that would need to be used with it, ensuring that both the fluids and the mechanical parts would work together as a system.
Thermal inkjet print heads are less expensive than PIJ print heads and are usually easier to maintain. TIJ printers were designed for mass production and scalability, so they have many high-volume industrial printing operations applications.
Valve jet, which is also known as mechanical inkjet (MIJ), works by forcing pressurized ink through a large nozzle that is opened and closed by a mechanical actuator. An array of these fluidic valves can throw drops of ink across large distances thanks to the high pressure applied by the mechanical actuator. This allows for printing very large patterns, which is useful for marking materials like lumber and carpeting.
MIJ technology incorporates larger parts in its printers, which means it’s generally slower than competing DOD print heads. However, the viscosity range for valve jet ink is much broader than other inkjet technologies. This means MIJ can be used with high solid content inks like ceramic glazes and other abrasive materials, making it extremely popular in industrial applications.
This basic history of inkjet product printing and coding helps explain the competing technologies that are still in use today. All modern inkjet printers share a common ancestor, but each has improved upon the original technology to adapt to the changes in materials, manufacturing processes, and consumer demands over the last few decades.
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