Some twenty years ago I interviewed a printer who certified as a bond and shares printer. He challenged me to see the difference between a 1200 dpi text printed with a monochrome laser printer and the 3600 dpi version printed with his Heidelberg press. Even with his 10x loupe, I couldn’t, and neither could he. Industrial inkjets such as EFI’s VUTEk and Jetrion range or Océ’s Jetstream models are closing the gap with screen print and increasingly also with offset by using a trick called variable drop grayscale technology.
Grayscale printing doesn’t mean you’re going back to monochrome times, but involves changing the amount of ink fired into each pixel, depending on image data. This creates an illusion: a higher resolution than the one the printing engine is capable of. For example, a print head with a resolution of 600 dpi using one size ink droplets will output 600dpi material. However, if a printer has the ability to fire droplets as fine as 6 pL or less, it will produce sharp, precise images with smoother transitions, while firing larger droplets up to 36 pL or more delivers denser, more uniform solid image areas. The resulting image quality competes favourably with genuine resolutions of 1,200 dpi or higher. Additionally, the variable drop technology uses up to 35% less ink than fixed droplet printers.
Francis McMahon, VP marketing of the production printing systems department at Océ North America, notes two compelling reasons for the likely emergence of inkjet as the dominant colour printing technology: “The first has to do with ink costs and availability. Inkjet inks are widely manufactured, lower priced, and more versatile. They include pigment, dye-based, UV, solvent, and aqueous inks. The second reason is the flexibility of the technology itself. It’s relatively compact. It’s extendable, either by adding inkjet printheads or replacing existing ones with faster versions. It allows brightly saturated, vibrant color printing on an array of media.”
SGIA spoke to Chris Lynn, Vice President of Sales and Marketing at Xaar America Inc. about the increased use of variable drop (or grayscale) technology for wide/grand-format printers. Mr. Lynn said: “Variable drop or grayscale printing combines the image quality that is achievable using the smallest drop size with the productivity achievable with the largest. Therefore, a single pass head with 360 nozzles/inch and eight gray levels (6-42pl drop sizes), delivers an image quality that looks more like 900dpi at a speed of 80 ft/min. The speed or the image resolution also can be doubled by adding another printbar. The advantage of variable drop compared to binary inkjet is high-quality text and graphics in a single pass.”
EFI’s latest UV-curable digital press represents a true replacement for analogue equipment with the productivity of screen and image quality approaching offset. It is the 3.2 meter EFI VUTEk HS100 Pro, a high-speed digital UV press with productivity and image quality that will appeal to screen printers and the commercial sector wanting a cost-effective digital platform to produce longer sheet runs at a low total cost of ownership.
EFI’s Pin & Cure imaging technology, driven by the Orion OS platform, delivers precise ink lay-down for critical colour accuracy and consistency, gloss control and an increased colour gamut. This printer can fire drops of between 0 to 36 pL. With throughput speeds at rates of up to 100 boards per hour and up to 50 boards per hour in P-O-P mode, the VUTEk HS100 Pro comes with true grayscale print head technology and up to eight colours (a minimum requirement for a large gamut), including white and specials, for maximum ink yield and a low cost per print over analogue.
The Océ JetStream Dual series comprises the Océ Jetstream 1500, JetStream 2200 and JetStream 3000 models available with speeds of respectively 100, 150 and 200 meter per minute. They are all variable grayscale systems with droplet sizes from 5 to 12 pL and a perceived resolution of 1,200 dpi.