Industry colleagues in the field of digital printing have their own understanding and respected brands for the core components of printing equipment - inkjet print heads, and they also have certain requirements for the characteristics of print heads from different angles.
Some focus on cost, some focus on life, some focus on the ink compatibility range, and some focus on after-sales service. Of course, in the final analysis, print quality is the indicator that everyone pays most attention to, and it is also the product feature that all printhead manufacturers have been committed to improving.
As a latecomer in the inkjet printing market, Kyocera inkjet print heads stand on the shoulders of giants. It summarized the pain points and needs of the existing market and fully utilized its deep understanding of ceramic materials and organically combined the core technologies and experience accumulated in the electrical, audio, and mechanical fields. Based on it, Kyocera developed a piezoelectric inkjet print head with a whole-piece piezoelectric ceramic as the core. From the first day of entering the market, Kyocera print heads’ high print width, high ignition frequency, and high-precision print quality have received widespread attention and recognition from the market.
Even today, more than 10 years later, Kyocera inkjet print heads still have a strong advantage among all print head brands, and have almost become synonymous with high-end inkjet print heads. So where is the technical source of Kyocera print heads’ high print quality?
Kyocera Inkjet Print Heads: High-speed ejection
A key factor affecting the quality of printing is the accuracy and stability of the ink droplet landing point. The accuracy of the ink droplet landing point is also affected by many factors, such as the processing accuracy of the nozzles, the uniformity of the inductance of the piezoelectric ceramic, the stability of the ink temperature, and the printing spacing. However, except for the temperature and printing spacing, the above-mentioned factors cannot be changed after the printhead is manufactured. In other words, it mainly depends on the manufacturing process and processing accuracy. So when the mass-produced Kyocera inkjet print heads are delivered to users, how can we ensure that the printing accuracy of each nozzle is reliable?
First, during the processing stage, Kyocera has optimized and inspected the flow path and processing technology to ensure that all the printheads shipped out of the factory are of high standards. However, the physical processing technology used in nozzle manufacturing is not photolithography after all, which will cause slight differences within the tolerance range between the thousands of nozzles in a printhead, and such differences will also cause the flight speed difference of ink droplets spit out by different nozzles.
Single nozzle - 20μm diameter (5000x magnification)
The intuitive effect of this difference is that when printing a straight line perpendicular to the relative moving direction, the straight line will be slightly fluctuated after being magnified. Usually, this fluctuation can only be seen by the naked eye when it is 10~20 cm away from the printed screen.
However, as an industrial-grade printhead, Kyocera has developed a countermeasure to improve this tiny difference. Through the matching of high-performance piezoelectric sheets and waveforms, the initial velocity of the ink droplets when they are spit out is increased as much as possible under the premise of complete ink droplets, and the high flight speed of the ink droplets is used to compensate for the tiny individual differences between the nozzles. The effect of high-speed spitting speed is shown in the figure below.
High-speed spitting
(similar to the visual effect of real ink droplets magnified 100 times)
Ink droplet-one drop
When talking about image quality, a word that is often used to praise the image quality is "clean". So what is the fundamental difference between a "clean" image and a slightly "dirty" image?
When talking about a "dirty" image, colleagues in the industry will immediately respond with "floating ink (scattered dots), noise (satellite dots), and tailing". On the contrary, when talking about a "clean" image, there is only one standard: the ink droplets fall in a rounded shape, the edges are clean, and there is not a single ink spot in the blank space of the image. Kyocera has achieved such image quality.
Those who have a deep understanding of piezoelectric inkjet print heads know that each ink droplet is the result of the resonance of the sound waves generated by the deformation of the piezoelectric film. The resonance of the sound waves is the power source of inkjet, but if the residual sound waves are not properly handled, it will affect the formation of ink drops. Kyocera simulated the flow path and fluid, and emphasized the dual control of the transmission and suppression of sound waves in the flow path design during the research and development stage. On the basis of reasonable flow path design, combined with Kyocera's waveform debugging, it has achieved that each droplet volume can be reduced to a single drop of ink.
Kyocera Inkjet Print Heads: Control of droplet volume
Digital printing is also divided into two categories in terms of droplet volume, two-state printing and variable dot printing. Kyocera printheads belong to the latter, and achieve 4~5-order variable dot printing at high ignition frequency (30~40kHz). At the same printing concentration, the printing effect of variable dots is more uniform, especially when printing pure color blocks, delicate gradients and patterns with rich details, the advantages of variable dots are particularly obvious.
Kyocera's small droplets are a well-known feature and advantage. Small enough droplets that can ensure landing accuracy are essential for high-quality printing.
Kyocera KJ4B-YH water-based print head printing on white cardboard
(on-site mass production photo of the end customer)
Kyocera Inkjet Print Heads: Vibration suppression
It is not realistic to control the vibration of sound waves in the nozzle flow path in real time. Therefore, the printhead developers are required to consider the stability of ink supply, smooth transmission of sound waves and effective suppression of residual vibration during the design stage, and gradually optimize the design through flow path simulation technology, so as to achieve transmission or suppression through the flow path structure on the path of sound wave transmission. This is also another key technology for Kyocera inkjet print heads to establish quality barriers in addition to the core technology of piezoelectric ceramics.
Therefore, when Kyocera talks about print quality, it is actually talking about: how to increase the spitting speed; how to ensure that the ink droplets are one drop; how to accurately control the amount of droplets while ensuring the accuracy of the landing point; and how to achieve the suppression of harmful sound waves and the smooth conduction of beneficial sound waves through sophisticated flow path design.
To make good products, we need to maintain respect for technology, organically combine decades of technology accumulation, accurately grasp market needs and pain points, establish our own quality barriers, and constantly make up for shortcomings. Kyocera inkjet print heads have been sharpening their swords for ten years. It seems that there has been no innovation for a long time, but we have never stopped investing in new technology research and development and improving shortcomings. We hope to bring surprises to everyone in the next ten years.
