Following his post last week about the speed and scalability of your raster image processor, in this film, Martin Bailey, distinguished technologist at Global Graphics Software, explains how to determine how much raster image processor (RIP) power you need to drive a digital press by calculating the press data rate. It’s the best way of calculating how much RIP power you need in the Digital Front End (DFE) to drive it at engine speed and to ensure profitable printing.
If you’re building a digital press, or a digital front end (DFE) to drive a digital press, you want it to be as efficient and cost-effective as possible. As the trend towards printing short runs and personalization grows, especially in combination with increasing resolutions, more colorants and faster presses, the speed and scalability of the raster image processor (RIP) inside that DFE are key factors in determining profitability.
For your digital press to print at speed you’ll need to understand the amount of data that it requires, i.e. its data rate. In this film, Martin Bailey, distinguished technologist at Global Graphics Software, explains how different stages in data handling will need different data rates and how to integrate the appropriate number of RIP cores to generate that much data without inflating the bill of materials and DFE hardware.
Martin also explains that your next press may have a much higher data rate requirement than your current one.
Direct™ product manager Ian Bolton explores the impact of using software that has evolved from traditional print processes to drive digital inkjet presses as they advance to print faster, in higher resolution, a wider variety of colors and applications. In particular, Ian focuses on the impact that rising data rates have on the workflow:
Digital press software evolved from traditional print processes has already reached its limit. Digital presses are becoming higher resolution – most are moving from 600 dpi to 1200 dpi, quadrupling the data. They’re also becoming deeper, with up to 7 drop sizes – and these drops are being made from a wider variety of colors. Digital presses are also becoming wider, up to 4 meters wide, and faster, up to 1,000 feet per minute!
And what if you need to print where every item is different? For example, fully personalized – like curtains, flooring, wall coverings, clothing etc. All of these require software that can deliver ultra-high data rates.
Let’s look at how those data rates scale up as digital presses advance:
If we start with 600 dpi, 20 inches wide, 3 drop sizes and 100 m per minute, then that’s 120 MBps per colorant, which is not too challenging. But once we move up to 1200 dpi, we’ve now quadrupled the data to 480 MBps, which is the read speed of all but the most bleeding-edge solid state drives today.
With printhead, nozzle and roller technology improving, the rated speeds also increase, so what happens when we go up to 300 m per min? It’s now 1.4 GBps and you will need one of those bleeding-edge solid state drives to keep up, bearing in mind you will now be writing as well as reading.
And if we go wider to print our wallcoverings at 40 inches wide, we’re now at 2.8 GBps … and we want our walls to look great close up, so we might be using 7 drop sizes, which takes us up to 5.7 GBps … and this is all just for one colorant!
Based on these numbers, it should be clear now that, for this generation of digital presses and beyond, a disk-based workflow just isn’t going to cut it: reading and writing this amount of data to disk would not actually be fast enough and would require ridiculous amounts of physical storage. This is where software evolved from traditional workflows hits a barrier: the data rate barrier.
To solve this we need to go back to the drawing board. It’s similar to the engineering challenge of moving from propeller-driven aircraft to jets that could break the sound barrier. Firstly, you need to develop a new engine and then you need to commercialize it.
So, if you’re looking for software to power your first or next digital press it’s going to need the right kind of software engine that isn’t based on disk technology so that you can drive your digital press electronics directly and smash through the data rate barrier. In other words, you need to go Direct.
Ever wondered what a raster image processor or RIP does? And what does RIPping a file mean? Read on to learn more about the phases of a RIP, the engine at the heart of your Digital Front End (DFE).
The RIP converts text and image data from many file formats including PDF, TIFF™ or JPEG into a format that a printing device such as an inkjet printhead, toner marking engine or laser platesetter can understand. The process of RIPping a job requires several steps to be performed in order, regardless of the page description language (such as PDF) that it’s submitted in. Even image file formats such as TIFF, JPEG or PNG usually need to be RIPped, to convert them into the correct color space, at the right resolution and with the right halftone screening for the press.
Interpreting: The file to be RIPped is read and decoded into an internal database of graphical elements that must be placed on the output. Each may be an image, a character of text (including font, size, color etc), a fill or stroke etc. This database is referred to as a display list.
Compositing: The display list is pre-processed to apply any live transparency that may be in the job. This phase is only required for any graphics in formats that support live transparency, such as PDF; it’s not required for PostScript language jobs or for TIFF and JPEG images because those cannot include live transparency.
Rendering: The display list is processed to convert every graphical element into the appropriate pattern of pixels to form the output raster. The term ‘rendering’ is sometimes used specifically for this part of the overall processing, and sometimes to describe the whole of the RIPing process.
Output: The raster produced by the rendering process is sent to the marking engine in the output device, whether it’s exposing a plate, a drum for marking with toner, an inkjet head or any other technology.
Sometimes this step is completely decoupled from the RIP, perhaps because plate images are stored as TIFF files and then sent to a CTP platesetter later, or because a near-line or off-line RIP is used for a digital press. In other environments the output stage is tightly coupled with rendering, and the output raster is kept in memory instead of writing it to disk to increase speed.
RIPping often includes a number of additional processes; in the Harlequin RIP® for example:
In-RIP imposition is performed during interpretation
Color management (Harlequin ColorPro®) and calibration are applied during interpretation or compositing, depending on configuration and job content
Screening can be applied during rendering. Alternatively it can be done after the Harlequin RIP has delivered unscreened raster data; this is valuable if screening is being applied using Global Graphics’ ScreenPro™ and PrintFlat™ technologies, for example.
A DFE for a high-speed press will typically be using multiple RIPs running in parallel to ensure that they can deliver data fast enough. File formats that can hold multiple pages in a single file, such as PDF, are split so that some pages go to each RIP, load-balancing to ensure that all RIPs are kept busy. For very large presses huge single pages or images may also be split into multiple tiles and those tiles sent to different RIPs to maximize throughput.
To find out more about the Harlequin RIP, download the latest brochure here.
If you’re in the process of choosing or building a digital front end for your press, you’ll need to consider how much RIPing power you need for the capabilities of the press and the kinds of jobs that will be run on it. The RIP converts text and image data from many file formats including PDF, TIFF™ or JPEG into a format that a printing device such as an inkjet printhead, toner marking engine or laser platesetter can understand. But how do you know what RIP is best for you and what solution can best deliver maximum throughout on your output device? This is the first of two posts by Global Graphics Software’s CTO, Martin Bailey, where he advises how to size a solution for a digital press using the data rate required on the output side.
Over the years at Global Graphics Software, we’ve found that the best guidance we can give to our OEM partners in sizing digital press systems based on our own solution, the Harlequin RIP®, comes from a relatively simple calculation of the data rate required on the output side. And now we’re making a tool to calculate those data rates available to you. All you need to do is to download it from the web and to open it in Excel.
You will, of course, also need the specifications of the press(es) that you want to calculate data rates for.
You can use the spreadsheet to calculate data rates based on pages per minute, web speed, sheets or square meters per minute or per hour, or on head frequency. Which is most appropriate for you depends on which market sector you’re selling your press into and where your focus is on the technical aspects of the press.
It calculates the data rate for delivering unscreened 8 bits per pixel (contone) rasters. This has proven to be a better metric for estimating RIP requirements than taking the bit depth of halftoned raster delivery into account. In practice Harlequin will run at about the same speed for 8-bit contone and for 1-bit halftone output because the extra work of halftoning is offset by the reduced volume of raster data to move around. Multi-level halftones delivered in 2-bit or 4-bit rasters take a little bit longer, but not enough to need to be considered here.
You can also use the sheet-fed calculation for conventional print platesetters if you so desire. You might find it eye-opening to compare data rate requirements for an offset or flexo platesetter with those for a typical digital press!
Fortunately, the latest version of the Harlequin RIP offers a framework that can help you to meet all these requirements. It offers a complete scale of solutions from a single RIP through multiple RIPs on a single server, up to multiple RIPs across multiple servers.
In my next post I’ll share how the data rate number can be used to make a first approximation of which class of RIP integration you should be considering.
The above is an excerpt from our latest white paper: Scalable performance with the Harlequin RIP®. Download the white paper here.
Standards for variable data printing (VDP) have come a long way since the first work by CGATS to develop a universal delivery format in the late 1990s. In 2010 the International Standards Organization published the PDF/VT standard, marking the first really effective specification for a reliable, vendor-neutral exchange of variable data jobs, both within and between companies.
A special type of the PDF file format, PDF/VT is specifically used for variable data and transactional printing in a variety of environments, from desktop printing to high volume digital production presses. Built on PDF/X, it therefore brings all the advantages of that standard in enforcing best practices for reproducible and predictable color and appearance to the variable data and transactional print worlds.
The industry is gradually realizing its value to improve quality, competitiveness and productivity, and I’ve been working with the PDF/VT Competence Center, especially with Christoph Oeters (Sofha), Paul Jones (Teclyn bv) and Tim Donahue (technical consultant) to produce a new set of Application Notes highlighting the benefits of using PDF/VT and the workflows that it enables.
The Application Notes explain how to make the highest quality and most efficient PDF/VT files to achieve the required visual appearance of a job, so if you develop software to read and write PDF/VT files, for example in composition tools, RIPs, digital front ends and imposition tools, or if you work on print workflow integration, you’ll find the notes really beneficial. They also show how document part metadata can be applied and leveraged for VDP specific production workflows.
Of course, there are wider benefits to using PDF/VT: The adoption of PDF/VT will allow the industry to finally move towards a reliable, vendor-neutral exchange of variable data jobs, simplifying the process of variable data printing significantly.