Tested to destruction

_DSC8885_Web_RicohITCEarlier this year Ricoh set up a European Inkjet Technology Centre at its sprawling base in Telford, UK, to support sales of its inkjet printheads and I went along to check it out.

The Ricoh printheads are essentially stainless steel units that are bonded together with laminates to form the fluid chamber and ink channels. Using stainless steel means that the heads are compatible with many different types of ink, including UV, solvent, oil and water. They are used in various markets, including wide format, which accounts for over half the uses, as well as 3D, textiles and ceramics.

The main R&D work in developing them is carried out in Japan but the new centre will complement an existing facility in the US that works with customers to understand their applications. Part of this involves feeding customer requests back to the main development teams. But much of the work involves testing customer inks, as Graham Kennedy, business development manager for Ricoh’s industrial print division explains: “It’s important that we understand the chemistry that our customers are looking to put through the head, so we qualify and grade the inks for use with our head technology.”

This involves what amounts to a torture chamber for printheads.  Ricoh carries out a number of tests to see how the inks react with the heads, such as soaking the heads within the inks and leaving them for a set amount of time before measuring the effect on the adhesive used within the printheads.

_DSC8890_Web_RicohITCAnother test involves the way the ink reacts to the coating that Ricoh puts on the nozzle plate to ensure that waste ink will sit on the surface and can be easily cleaned away. Keeping the nozzles free of ink that might otherwise dry and cause them to become blocked is a key part of prolonging the lifespan of a printhead. But some inks can react adversely with the coating. Kennedy adds:  “We can change the type of coating but some customers use it without a coating.”

Ricoh also tests for whether or not the inks will cause corrosion within the heads, which is a particular cause of concern with water-based inks such as latex inks. It’s not normally an issue with stainless steel but can affect the metal diaphragm, which is a nickel alloy. The actual corrosive penetration can be measured to give a value of mm/ year of corrosion, with samples from the past that have failed in the field that are used as references.

They also measure the viscosity of the inks in order to see how well the droplets form and when the tail breaks off. This involves dropping 0.5 ml of ink and measuring it. A water bath is used to control the temperature but if the ink is too viscous to flow properly then the temperature can be increased to reduce the viscosity range. But Masohiro Yagi, senior sales engineer, points out: “Sometimes UV ink will cure thermally so we have to be careful, but most inks are fine below 60°C.”

Ricoh also supplies the electronics to drive the printheads, which are analogue and so need a digital signal to fire the ink, though some customers prefer to supply their own. Ricoh develops a standardised waveform to fire the heads, but most customers will adapt this as it’s a key element in ensuring that a given ink can be jetted through the printheads.

Ultimately, the main aim behind this facility is to help Ricoh sell more printheads to its OEM customers. So, even though these printheads end up making the ultimate sacrifice, it’s good to know that it’s not in vain.

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