I was helping a client recently with a high page count print book with a short press run: 500 copies of a 488-page, 8.5” x 11” perfect-bound book. The inside text was to be 4-color throughout. I assumed that due to the short run length, this would be a perfect fit for a digital press. Since I had worked closely with a printer with an HP Indigo, I approached my sales rep with the specs, but I was surprised by her answer.
She said the print book would be cheaper to produce via offset lighography due to the 4-color process work on each page. She said the “click charges” would be a killer when you factored in four clicks per page (C, M, Y, and K) for 488 pages. So she bid the book for me on her commercial printing company’s offset equipment.
What Are Click Charges?
Most printers lease their digital printing equipment. They don’t own it. Therefore, digital press manufacturers charge printers a fee (a per-click charge) to cover the cost of maintenance (repairing equipment on-site to keep “down-time” to an absolute minimum) and sometimes consumables (liquid toner, for instance). This click charge is usually added on a per-page and per-color rate (i.e., the number of impressions made by the digital press). Therefore, the commercial printing supplier passes this cost on to the customer.
So the printer to whom I had bid my client’s job was saying that assuming 500 copies of a 488-page book with four click charges per page for cyan, magenta, yellow, and black, the price would actually exceed the cost to print the job via offset lithography.
How Does Digital Printing Compare to Offset Lithography?
A digital press (the HP Indigo in the case of the commercial printing vendor I was working with) produces four individual images (layered on top of each other) to create the full-color image on a blanket cylinder and then transfers the image from the blanket to the printing paper. Electrostatic charges hold the liquid toner (ink) on the blanket until it is transferred to the paper.
In a similar manner, an offset press prints an image, color by color, as the paper travels through the press, from inking unit to inking unit. The four printing plates (cyan, magenta, yellow, and black) produce an image on each press blanket, and the blankets transfer the four process images onto the substrate (one on top of the other). Once the press sheet has traveled through all four inking units, the paper has received images in all process colors laid over one another. (Keep in mind that process colors are transparent, so the cyan, magenta, yellow, and black images don’t obscure one another. Rather they work together to create and enhance the full-color images.)
You could say that digital and offset commercial printing are similar in that both transfer the final printed image onto a blanket and from the blanket onto the printing paper. Therefore, it didn’t surprise me that a bid on the HP Indigo digital press for my client’s four-color, 488-page book would be high and would actually cost more than an offset lithographic press run of the job.
What’s the Alternative?
With this in mind I was pleased to hear from a colleague that custom printing work priced for the HP T410 digital press was based on the actual use of printing ink rather than on a per-click charge.
So I did some research. The HP T410 is a large-format, roll-fed book press. Essentially it is a web press (much like an offset web press). But in this case instead of using printing plates, the digital press prints book pages via its array of inkjet print heads (like a huge, roll-fed version of a desktop inkjet printer).
When you compare the literature describing these two presses (HP Indigo and HP T410), you will see that the drying of the ink is handled differently on each machine. On an electrophotographic digital presses (the HP Indigo, for example), the image is already dry when it is transferred from the blanket roller to the substrate (all four colors transferred at one time). Therefore, there’s a lot of flexibility in what printing substrate you can use, because the dry image won’t seep into the paper fibers.
In contrast, on the HP T410, an inkjet press, the specification sheet references float infrared (IR) scalable dryer zones as the drying method. So basically a specific frequency of light will cure the ink (presumably instantly, as with UV inks, which are cured under UV light).
Why Does This Matter?
My colleague noted that there were no click charges for this digital printer, that clients only had to pay for color by the square inch. With this information, I did more research. I verified his claim (the product literature confirmed that you only pay for the ink you use).
Now this is a novel and rather dramatic claim for the following reason. In offset lithography, if you put any process-color images on even one page, you are still paying for 4-color on all pages on that particular side of a press sheet. (This may be 8 pages of a 16-page press form or 16 pages of a 32-page press form.) In short, you’re paying a lot to “open” a side of a press form to process color. So if you’re wise, you’ll take advantage of the expense and put process color on (many) other pages of this particular side of the press “form” (one side of a press sheet that will eventually be folded into a press “signature”) in order to distribute the cost.
In contrast, on the HP Indigo, if you print any process color on any individual page of a book, you’re charged for all four colors (four click charges). This is true even if your 4-color image is a small logo.
But based on HP’s literature, if you’re using the HP T410, your charge for the same process color distribution will be higher or lower depending only on the size in square inches of the color printed image.
For my client’s print book, pricing the job based on the amount of color rather than on the number of color pages may yield a huge savings. We shall see.
What I Would Need to See First
My assumption is that not all printers have the HP T410. In fact, I would assume that relatively few printers do. After all, the concept of printing books on a web press using inkjet technology is relatively new.
However, if I can find such a commercial printing supplier, and if the samples of inkjet printed work produced on coated paper compare favorably to the electrophotographic digital printing of the HP Indigo, I will be pleasantly surprised.
And the cost may just make the difference for my client.
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on Sunday, February 12th, 2017 at 5:02 pm and is filed under Digital Printing.
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