Tableware, tiles, corrugated cardboard, clothing, window frames, license plates—these are all items found around us. These products differ in use and materials, yet they share a common characteristic. That is, all of them can be printed onto using inkjet heads.
This time, we spoke with two individuals responsible for inkjet head product planning at SII Printek Inc., one of the Seiko Instruments group companies. We will introduce the company’s technology as it advances toward a new frontier in industrial inkjet printing, as well as the future that lies ahead.
Industrial inkjet printing is rapidly spreading. While it was once primarily used for printing on advertising signage, in recent years its applications have expanded to a wide range of materials and shapes, including ceramic tiles, corrugated cardboard, tableware, construction materials, and textile printing.
The greatest feature of inkjet printing is that it is “non-contact.” Because the head does not directly touch the print surface, it can handle uneven ceramic tiles and three-dimensional tableware. Conventional methods such as screen printing, gravure printing, and offset printing use printing plates, whereas inkjet printing is an on-demand method that does not require plates, enabling different designs to be output one by one.
“Over the past 10 to 15 years, ceramic tile printing has rapidly shifted from analog printing to inkjet, and in our experience, more than 90% of the market now consists of digital printing. Corrugated cardboard printing is also gradually being replaced, and this trend is accelerating alongside the expansion of e-commerce,” explains Mr. Yamamura, General Manager of the Planning and Sales Department.
In recent years, inkjet printing has also gained attention not only for “printing beautifully” but also as a means of expressing material textures and adding functionality. For example, by layering transparent ink to create surface relief or by dissolving surfaces with special inks to reproduce the feel of wood grain, inkjet technology is moving beyond 2D printing into the realm of material processing.
Inkjet printing is also attracting attention from an environmental perspective. In conventional analog printing (such as screen and gravure printing), a certain amount of ink waste is generated during color changes and cleaning processes. In contrast, the inkjet ejects ink only where needed, significantly reducing ink loss. In textile printing, the spread of water-based pigment inks has greatly reduced the amount of water used in cleaning processes, and in Europe, legal frameworks are being developed—particularly in the textile industry—positioning inkjet as an environmentally friendly printing technology.
What SII Printek manufactures is the “printhead,” the component that can be considered the heart of industrial inkjet printers. Rather than the printer body itself, the company handles the core component that ejects droplets. Each unit is about the size of a B6-format paperback (approx. 5 x 7 in), and it is not uncommon for more than 100 printheads to be installed in a single industrial printer.
All manufacturing is carried out at the company’s own factories in Japan. The Takatsuka facility in Chiba Prefecture handles the upstream processes for the core component, the piezo actuator, while the Akita facility in Akita Prefecture is responsible for the downstream assembly processes.
The company’s printheads use a piezo (piezoelectric) system. A piezo actuator is a ceramic piece (piezoelectric element) that deforms when voltage is applied. This deformation is used to push out ink, enabling the high-speed, high-precision ejection of extremely small droplets on the order of picoliters (one trillionth of a liter).
The grooves through which ink is ejected are several tens of microns wide—finer than a single strand of hair. The processing technology (dicing) that precisely cuts these microscopic grooves one by one is one of the foundations of the company’s manufacturing capabilities. Piezoelectric ceramics are brittle and are known to be prone to cracking during machining. The ability to process them stably at a mass-production level is due to the accumulated watchmaking technologies of our parent company, Seiko Instruments.
“RC1536,” SII Printek’s flagship product, was originally developed for ceramic tiles. However, it is now used across a wide range of applications, including corrugated cardboard, textiles, glass, metals, and 3D additive manufacturing.
While many manufacturers in the industry pursue miniaturization and thinning of heads to improve resolution, our company deliberately chose the opposite direction. Our design philosophy is to maintain a large piezo actuator volume to secure power.
A larger head size is a disadvantage in terms of compactness. However, it also leads to the strengths of RC1536, including high-gap capability, high-volume ejection, and support for high-viscosity inks.
● Maximum gap: 20 mm
● Droplet range: 13-150 pL (picoliters) (RC1536-M), 25-225 pL (RC1536-L)
● Supported ink viscosity: 10-30 mPa-s (Typical: 5-10 mPa-s)
RC1536 has a wide print width and can eject large volumes, allowing the number of heads installed in a printer to be reduced. For example, in glue printing on ceramic tiles, where competing heads may require four bars, RC1536 can handle the task with just two bars, contributing to overall cost reduction of the printer.
It also supports water-based inks, which allow for lower costs due to higher water content and reduced environmental impact. This has strengthened RC1536’s presence in the Chinese market, where environmental regulations are strict and cost efficiency is required.
In addition to water-based inks, it also supports a wide variety of ink types, including solvent, UV-curable, and oil-based inks.
The first strength of SII Printek’s flagship product, RC1536, is its high-gap capability. This refers to the ability to accurately place droplets even when the distance (gap) between the head and the printing target (media) is large.
Accordingly, in developing RC1536, we increased the droplet ejection speed by approximately 1.8 times compared to conventional models. By ejecting droplets at high speed, the influence of slight air currents is minimized, allowing accurate delivery to media positioned at a distance.
This high-gap capability was initially developed with ceramic tile printing in mind. However, it has since proven useful in applications beyond the original scope, including warped low-cost corrugated cardboard, deep tableware interiors, and uneven construction materials. “Through repeated testing at customer sites, we discovered features even we were not aware of,” recalls Mr. Yamashita, Section Manager of the Planning and Sales Department.
Currently, there are cases of successful printing at gaps of up to approximately 50 mm, and the product has secured a high share in tableware (porcelain) printing markets in China and Europe. In the future, combining it with robotic arms is expected to enable printing from various angles and orientations, further expanding application fields.
The second strength is the ink circulation structure. RC1536 is designed with ink inlet and outlet ports on both sides of the head, allowing ink to circulate continuously inside the head during printing.
This mechanism addresses the long-standing issue of “nozzle clogging” in industrial printing. Pigment particles in the ink (especially inorganic pigments used for ceramic tiles, which tend to be heavy and hard) can settle and block nozzles, or air bubbles can interrupt ejection. Continuous ink circulation suppresses these causes and maintains stable ejection. It also offers advantages such as eliminating ink loss during filling.
During development, a key technical challenge was how to keep internal pressure differences caused by circulation within acceptable limits. If pressure differences become too large, droplet size will vary between nozzles, affecting print quality. We derived the optimal internal structure through repeated fluid simulations and real-machine testing.
The third strength is the “grayscale function,” which flexibly controls droplet size, along with support for high-viscosity inks.
A single droplet is extremely small at about 10 picoliters, but by continuously ejecting multiple droplets from the same nozzle and merging them in flight, droplets exceeding 200 picoliters can be formed. This allows fine details to be expressed with small droplets, while solid areas can be printed quickly and densely with larger droplet, enabling digital control suited to each application.
While the typical viscosity range supported by industrial inkjet heads is about 5-10 mPa-s (millipascal-seconds, an SI unit indicating a fluid’s viscosity or resistance to flow), RC1536 supports a broader viscosity range of 10-30 mPa-s. This enables compatibility with various inks, including water-based, UV, solvent, and oil inks, for use in diverse applications.
The source of SII Printek’s technological strengths lies in the precision processing technologies it has built over many years. “SYOism” is the technological philosophy upheld by the Seiko Instruments Group, and the printhead business embodies this philosophy.
Precision dicing of piezoelectric ceramics applies technologies originally developed for cutting quartz resonators. The meticulous, craftsmanship-driven manufacturing culture—assembling components under a microscope using tweezers and ultra-small screwdrivers—stems from the expertise accumulated through watchmaking at Seiko Instruments. These technologies enable the mass production of printheads with grooves finer than a human hair.
The origins of the business date back to the late 1990s. Within Seiko Instruments, efforts began to explore whether a new business could be created leveraging the company’s own technologies. By combining patented technologies held by overseas printhead manufacturers with its own mass-production processing technologies, the company successfully commercialized inkjet heads. Mr. Yamashita, Section Manager, reflects, “It was precisely our company’s unique precision processing technologies that made mass production possible.”
The development approach of directly measuring droplet flight using an in-house “Droplet Observation System” and physically verifying simulation results reflects a philosophy not of simply accepting good results, but also of thoroughly confirming whether outcomes match intended targets, a mindset cultivated through the precision measurement culture of watchmaking.
RC1536 was originally developed for the ceramic tile market. Today, however, its applications are rapidly expanding to corrugated cardboard, tableware, window frames, license plates, and even the bio and medical fields.
In the medical and bio fields, inkjet technology is being studied for applications requiring precise dispensing of fixed quantities at specific positions. We have already received inquiries for testing in these areas. Applications such as micro-dispensing of diagnostic reagents and applying biomaterials to cell culture substrates are emerging, requiring droplet control technologies in entirely new contexts.
Mr. Yamamura, General Manager, comments as follows.
“Inkjet technology originally began with printing text and photographs. However, going forward, applications beyond printing—such as creating surface textures, adding functionality, and dispensing chemicals—will continue to expand. It is already being used in surprising applications in the bio and medical fields.”
Behind these “unexpected discoveries” is the company’s proactive approach of working closely with customers during testing. When inquiries arise, staff visit customer sites and finely adjust ink types, machine specifications, and ejection waveform settings. By carefully optimizing the “trinity” of head, ink, and machine in this way, the company is opening up new applications.
We entered the ceramic tile market—then largely untapped—around 2001-2002. Today, we hold a top global share in the inkjet head market for tiles and rank among the leading group in the European corrugated cardboard printing market. We also maintain strong competitiveness in tableware (ceramic) printing. These achievements result from the alignment of our precision processing technologies and unique technical characteristics—high gap, high volume, and ink circulation—with market needs.
Inkjet technology is now expanding beyond the framework of “printing” into manufacturing processes, functionalization, and even medical and bio fields. Mr. Yamamura states, “We believe it will continue to be used in applications that even surprise us.” Beyond that surprise lies the next frontier for SII Printek.
Interview cooperation
From left: Mr. Yamamura, General Manager of the Planning and Sales Department; Mr. Yamashita, Section Manager