Seiko Industrial Instruments has introduced a new inkjet printhead, the RCH1536, which is an update to the existing RC1536, but with the promise of more durability and uniformity. The existing RC1536 features recirculation of the ink through the head and behind the nozzles so that it already has a good reputation for reliability in applications such as textile and ceramic printing.
The RCH model features a metal nozzle plate which Aliasgar Eranpurwala, head of sales for inkjet printheads for Seiko Instruments in Germany, says is a first for a head designed around the shear mode approach. This involves flexing the walls of the ink chamber to eject the ink droplet and requires a degree of flexibility, which is why most of these heads come with plastic nozzle plates. The Shear mode method was developed by Xaar and is also used by those companies that started by initially licensing head technology from Xaar, which includes Seiko as well as Konica Minolta and Toshiba Tec.
Eranpurwala says that it took the engineers two years to perfect the metal nozzle plate, explaining: “Finding the right thickness of the nozzle plate, finding the right materials, finding the right glues – it was a lot of work.”
He says that this gives the head a more industrial look though it’s not been available for long enough in the market place to be sure if it actually is more robust. However, he notes that a metal nozzle plate is easier to clean without scratching than plastic, saying: “So that’s where we think that it will help in the durability and the long lasting nature of our print heads.”
The new head has the same electronic interface and the same plumbing as the existing RC1536, so that it can be used as a drop-in replacement. Eranpurwala says that this backwards compatibility is very important: “The idea is to let existing customers expand their market segment.”
Eranpurwala says that the waveforms may change since the metal plate will affect the movement around the nozzles. He told me: “That might just be a software change and it may be just increasing the voltage.”
Otherwise the RCH head has the same 108.3mm print width of the RC1536 head, with the same drop sizes and running at the same speed. As the name implies, the head contains 1,536 nozzles, which are arranged in four rows, with 384 nozzles per row. This equates to 360 dpi resolution.
Eranpurwala explains that each nozzle has two electrodes which are used to fire a drop out of the printhead, adding : “We take a piezo element. We dice the channels in it. Then we do a process of sputtering where we put the electrodes on to their piezo elements to make them drivable, to give an electronic signal to it and to move the piezo so that a drop can be jetted out. Putting these electrodes on the piezo is a little challenging as you can imagine as the sizes are all at micron levels.
He says that for this new version Seiko has managed to improve the way these electrodes are applied, which allows for an even amount of energy to be transferred to the drops, regardless of whether or not that nozzle is located at the end or middle of a row. He adds: “That’s important when you want to print something wider, when you are printing single pass or printing unique colours. It’s important to get the same amount of drop sizes and drop speeds coming out of the printhead, and that’s what we’ve achieved with the RCH print head.
Seiko has also extended the fluid compatibility so that it will work with more inks. This involved finding new glues to use within the head since some fluids will cause the adhesives that bond the layers together to break down. Naturally the new RCH version will also work with all the inks that have already been certified for use with the existing RC version.
He says: “We have done a lot of testing in the market and the customers are very happy with it,” adding “We have tested it with automatic cleaning and compared it with the old head, which shows some wear and tear, but the metal didn’t show any wear and tear after 2000 actuations.”
The RCH head is aimed at industrial markets such as corrugated and ceramics as well as coding and marking. Initially it will only be offered for use with UV inks as Seiko will need to carry out more testing to understand how water-based inks might interact over time with the metal nozzle plate, since water doesn’t generally play nicely with water. However, it’s worth noting that the existing RC version does also work with oil and solvent-based inks, and there is an RCA variant for water-based inks.
The RCH 1536 printhead is already available though Seiko hasn’t got around to publishing the technical details yet. There is a choice of two native drop sizes, medium and large, as is also the case with the existing RC head.
Seiko has also developed a higher resolution print head, the RCE2560, which will offer up to 600 dpi resolution. This is still in progress and is likely to be announced commercially next year.
You can find further details on Seiko’s printhead range from seiko.instruments.de. There is also a YouTube video from the FuturePrint Tech conference earlier this month where Eranpurwala discusses the RCH 1536.
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