After numerous visits to the printing plant where the Landa Nanopress is running, I have a pretty good idea of how that machine works. I am assisted by a very nice diagram on the wall adjacent to the machine.
Fundamentally, the Landa Nanopress is a production ink-jet printing press. Its maximum sheet size is B1, or 1000 mm x 700 mm (the press is slightly larger than B1). The ink is water-based pigment. There are seven colors on this model: CMYK, plus orange, green, and blue/violet. These additional colors add tremendously to the color gamut of the press, making it one of the largest of any production press.
The ink-jet heads are made by Fuji/Dimatix. The resolution of the machine is 1,200 spi (machine spots per linear inch), meaning that the resolution of the ink-jet heads is 1,200 spi. The resolution in the other axis – belt direction – is 600 spi, which is a function of belt speed and other factors (likely the speed with which electronic instructions can be delivered to the heads). This resolution is comparable to toner-based printers like the Konica Minolta production machines which also have 1,200 spi resolution.
Offset presses, by comparison, use aluminum printing plates that are imaged on machines with at least twice that resolution, typically 2,400 spi. A Kodak Trendsetter can render 2,400 spi images – and more – with its combination of extraordinary feed accuracy and laser imaging precision. Another machine with which I have experience is the Spark from ESKO, which has over 5,000 spi resolution.
Both of those machines are capable of “currency” resolution. The Landa press is not in that league.
However, for commercial quality printing, the Nanopress is capable of producing competitive quality with an expanded color gamut, the combination of which makes it a formidable machine in the marketplace. This is especially true for general commercial printing in short runs in nearly any category of printing. The example I wrote about in my last blog shows that this machine can print very high quality books in short runs at an economical price. Wth no plates, and a very short make-ready, the machine is a true short-run production printing press.
To understand the path of ink-to-paper, you can follow the accompanying diagram.
A job is imposed into pages and forms (a form is one complete side of one press sheet). The press can print on both sides of the sheet in one pass through the press, where most offset presses cannot do this.
Prepress for the Landa machine is similar to that for any offset press. A skilled prepress operator assembles files – typically PDF files – into their component parts, and then positions those parts in the correct locations for printing. This could be as simple as two large “pages” for a full-sheet poster, or it could be many smaller pages imposed for a book. In any event, the elements of the printing job are made into complete forms, then crop and bleed marks, register marks and labels are added to make the forms ready to print.
The prepared forms are sent to the EFI Fiery RIP that is embedded in the Nanopress. This device is customized to run the Nanopress with its seven-color ink system, and capable of delivering data to the Landa electronics about the colors and positions of every imageable spot in all seven colors on the press sheet – both sides, and at a rate that keeps the machine running at its production speed of 6,500 impressions per hour.
The press operator moves the files through the Fiery, and it in turn creates all of the instructions necessary to run the machine – instructions that fire an ink-jet nozzle at every possible location on the press sheet in every color. Those files are supplemented by machine instructions for paper feed, ink volume, drying temperatures, perfecting (as required), coating (optional) and delivery. The complexity of the systems on this machine is greater than that of an offset press because the machine is not only moving and putting ink on paper, the Nanopress is imaging billions of microscopic ink-jet spots on that paper as it goes through the press.
The image starts on the ink-jet Print Bars. When running, the print bars emerge from air-tight parking places and move to hover over the Imaging Belt. When instructed to do so, the ink-jet nozzles are activated, and thousands of microscopic droplets of ink are ejected from the print bars onto the moving imaging belt. Collectively, the image is made up of potentially billions of ink-jet droplets deposited onto the moving belt.
In general, printing presses image the darkest color first, and then work their way to the lightest color. This is true for the Nanopress. All of the ink is deposited onto the belt, which then moves under a series of air dryers whose purpose is to dry the thin film of ink on the belt. By the time the ink film reaches the right-hand end of the press, the image is dry.
The belt carries the ink around the corner and then turns left and into the press where it meets a sheet of paper that has been fed into the cylinders. As the image on the belt comes in contact with the paper, the thin film of ink is transferred by pressure from the belt to the paper. This transfer takes place between Blanket Cylinder 1 and the first Impression Cylinder (with the belt and paper between).
The ink on the paper is completely dry when it emerges from the pinch of those two cylinders.
The paper is then passed around an intermediate cylinder and on to a Perfecting Cylinder which can either pass the sheet onward, or flip the sheet over, handing its trailing edge to the next Blanket and Impression cylinder pair for printing the other side.
This technique requires that the front side and back-side images must be printed to the belt in alternating order to perfect a sheet. So, when perfecting, the belt will carry images in front-back-front-back order. If the sheet does not perfect, then there would be only one side imaged to the belt, and it will double the output of the press by printing only the one side of each sheet.
On an offset press, one tries not to lose control of the gripper-edge by delivering the trailing-edge of the sheet to the gripper. On Heidelberg presses, for example, the perfecting system flips the sheet when perfecting, but maintains register by holding on to the original gripper edge – even when it is feeding the opposite direction into the press when perfecting. I don’t know if the Nanopress does this, but I would be surprised if it does not.
Front-to-back register is controllable on the press console with register cameras capturing images of the register marks on both sides of the sheet as it is imaged.
Once both sides of the press sheet are imaged, the paper is carried toward the delivery pile. Along this path there is another set of cylinders that can optionally hand the sheet to a conventional coating unit (part of the Komori press components). Here, an aqueous liquid coating can be applied to the sheet on both sides if desired.
The press sheet is carried by the delivery chain and dropped onto the receding delivery pile. The printing is then complete.
When the press goes to its idle stage, the seven ink-jet bars recede into parking places where the heads are kept away from dust and air in the machine. Both humidity and temperature are maintained in these parking spaces to protect the ink-jet heads, keeping them ready to run the next job.
At Blueprint, they keep the press warm and humidified 24 hours a day. The press is run for two shifts, and stands idle for the third shift.
Post-press operations – cutting, folding and binding – can commence immediately because the press sheets are completely dry the moment they arrive at the delivery. Offset printing would be allowed to dry for at least a few hours before commencing on these operations.