Ilisna O’Reilly, Sales Manager Southern Africa at NUtec Digital Ink, says nozzle open time (also known as decap time or latency) refers to the duration that a nozzle remains open when a printer is idling or not firing. This is critical in ink chemistry because it directly affects print quality, reliability and the operational efficiency of the ink and the equipment.
When a digital printer is not being used, is inactive, dormant or in standby mode, things can go wrong, especially because the nozzles on a printhead want to be firing and used for what they are intended. This is why chemistry matters. The nozzle open time ‘decap’ relates to how long the printhead/ ink can be left in idling mode and the print will still be of good quality. Most digital printing equipment runs a circulation or ‘spitting’ function that assists with nozzle open time when the ink channels or printers are not in use.
We want the inks to dry quickly on the media, what we don’t want is for the ink to dry in the printhead. This is where the chemistry comes in.
In the real world, no printer is operational 24/7/365 and printers often pause between jobs. The nozzle open time in this case would mean that the ink does not dry/cure in the nozzles during this downtime. Good nozzle open times ensure that the inks stay fluid and are ready to fire on demand.
When developing ink chemistries, nozzle open time is one of the many crucial factors our R&D chemists focus on. Not only must the ink have a good decap during idling or standby mode, but it must be stable under varying temperatures and humidity. The components that relate to this ‘balancing act’ are humectants, solvent volatility control, as well as surfactants and co-solvents.
We focus hugely on optimising nozzle open time to ensure longer idle duration without clogging when the machine is idling or not in use. This ensures improved print consistency and minimises printer operator interventions to do multiple cleans after the machine has not been in use.
Different ink types have different nozzle open times. UV has longer nozzle open times when compared to solvent, while water-based inks have the shortest nozzle open times. UV-curable inks don’t dry until exposed to UV light, whereas solvent-based inks start evaporating as soon as the printer is in idle mode.
If for whatsoever reason the printer will not be used for periods longer than 1-2 weeks, consult the relevant maintenance guide and follow the ink manufacturer’s recommendations on how to prevent the ink drying in the printhead nozzles.
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NUTEC DIGITAL INK
https://nutecdigital.com
