What is “Drop-on-Demand” Printing?
In industrial inkjet printing, there are two basic kinds of printheads: Continuous Inkjet (CIJ) heads and Drop-on-Demand (DOD) heads. At Engineered Printing Solutions, we specialize in DOD industrial inkjet printing machines. What is the difference between the two technologies, and what are the advantages and disadvantages of each? This post will explore these questions. But first, a quick explanation of the two differing technologies.
As the name implies, CIJ printheads dispense a continuous stream of ink. The ink that is not needed for the print job is collected and recirculated back to the reservoir. With drop-on-demand inkjet printing, the printhead dispenses ink only when needed. Drop-on-demand technology, when combined with variable drop sizes, permits greyscale printing, creating both photorealistic gradients and also vivid blacks, even on porous surfaces such as corrugated cardboard.
Continuous inkjet printing is an older technology. The advantages that it provides include high drop velocity, permitting longer throw distances and faster throughput rates. Additionally, since the nozzle is in continuous use, clogging is not usually a problem. Drawbacks to CIJ printing include a high degree of wasted ink due to recirculation, and also the need for solvent-based inks in CIJ printheads.
Drop-on-demand inkjet printing, on the other hand, uses only enough ink to create the image, and DOD printheads can create gradients and greyscale effects at effective resolutions of 1200 dpi and higher. With the use of fast-curing UV-LED based inks, DOD inkjet printers can match the throughput rates of CIJ systems at a fraction of the unit cost.