Shade and color variation in textile printing – why it’s important and what you can do about it

Printing soft furnishings

With fewer design limitations, a faster turnaround, no minimum run length and higher margins (not to mention reduced use of power and water, and of pollution), it’s not surprising that the digitally printed textile market is growing.1 Inkjet has certainly made textile design and printing much more flexible than screen printing – and that goes for everybody involved, from the designer through the printing company, to the buyer.

But printing textiles on inkjet doesn’t come without its challenges: as a software provider focusing on print quality issues, we often hear from print service providers who can only digitally print two thirds of the jobs they receive because they would not be paid for the quality they could achieve on the others.

Shade or color variation is a common problem. It’s not new in digital printing (it’s always been an issue for screen-printed and dyed textiles as well) and is usually managed by providing a shade band, which printer operators refer to, to check allowable color variations between pieces.

But, unlike screen-printing or dyeing, the color variation on an inkjet press can be visible over a small distance, just a few centimeters, and this results in visible bands across the output. Banding describes features that tend to be 1 – 10 cm across and they’re often caused by variation of inkjet pressure or voltage differences within the head, which typically results in a frown or smile shape. We also see a certain amount of manufacturing variation between heads so that one may print lighter or darker than the head next to it in a print bar. Some types of heads can also wear in use, which can result in less regular banding that can change over time. This means that large areas which should be flat color may not be.

When such a variation occurs it can greatly complicate a lot of post-print steps, especially if you need to put more than one piece of textile together, either in sewing or use (such as a pair of curtains). If that’s the case, then a significant difference may be unacceptable and your printing rejected by your buyer. Ultimately this leads to print service providers rejecting jobs, because they know their digital press can’t handle printing those tricky flat tints or smooth tones.

What can you do about it?

The first thing many companies do to try to overcome this banding is to adjust the voltage to the inkjet head, but this is often time-consuming and expensive because it requires an expert technician. A better alternative is to make the correction in software, which is a more cost-effective and faster solution. It means it can be automated and can act at a much finer granularity, so printing is more accurate. There’s no need to mess with controls that could damage the press, and printing companies themselves can make corrections without the vendor sending a technician on-site.

Our solution at Global Graphics Software for improving banding is PrintFlat™. It corrects tonality to hide banding based on measurements from the press. It adjusts every nozzle separately and doesn’t need a specialist engineer to make press adjustments. PrintFlat can be integrated into different digital front ends, using a variety of RIPs, including Caldera and Colorgate and, not to mention, our own Harlequin RIP®.

Over the years of working with many press manufacturers we’ve discovered that many technical issues and solutions are common across different sectors, including transactional, wide-format, commercial, labels and packaging, and industrial, including ceramics, wall coverings, flooring and of course textiles. That means that we already have years of experience in correcting for banding. Using PrintFlat in your press means print service providers can now take on those jobs they would normally reject.

To learn more about how to eliminate shade and color variation when printing on an inkjet press, listen to Global Graphics Software’s CTO Martin Bailey’s talk for FESPA 2020:

“New techniques to eliminate in-lot shade variation when printing textiles with inkjet.”

Or visit the PrintFlat website: https://www.printflat.com/

Further reading:

  1. What causes banding in inkjet? (And the smart software solution to fix it.)
  2. Streaks and Banding: Measuring macro uniformity in the context of optimization processes for inkjet printing

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  1. Digitally printed textiles are estimated to be between 2% – 5% of the total printed textiles market. Estimated at $146.5 billion in 2018 by Grand View Research

There really are two different kinds of variable data submission!

There are two completely different forms of variable data handling in  the Harlequin RIP®, and I’m sometimes asked why we’ve duplicated functionality like that. The simple answer is that it’s not duplication; they each address very different use cases.

But those use cases are not, as many people then expect, “white paper workflows” vs imprinting, i.e. whether the whole design including both re-used and single-use elements is printed together vs adding variable data on top of a pre-printed substrate. Both Harlequin VariData™ and the “Dynamic overlays” that we added in Harlequin version 12 can address both of those requirements.

Incidentally, I put “white paper workflows” in quotes because that’s what it’s called in the transactional and direct mail spaces … but very similar approaches are used for variable data printing in other sectors, which may not be printing on anything even vaguely resembling paper!

The two use cases revolve around who has the data, when they have it, whether a job should start printing before all the data is available, and whether there are any requirements to restrict access to the data.

When most people in the transactional, direct mail or graphic arts print sectors think about variable data it tends to be in the form of a fully resolved document representing all of the many variations of one of a collection of pages, combining one or more static ‘backgrounds’ with single-use variable data elements, and maybe some re-used elements from which one is selected for each recipient. In other words, each page in the PDF file is meant to be printed as-is, and will be suitable for a single copy. That whole, fully resolved file is then sent to the press. It may be sent from one division of the printing company to the press room, or even from some other company entirely. The same approach is used for some VDP jobs in labels, folding carton, corrugated, signage and some industrial sectors.

This is the model for which optimized PostScript, and then optimized PDF, PDF/VT (and AFP) were designed. It’s a robust workflow that allows for significant amounts of proofing and process control at multiple stages. And it also allows very rich graphical variability. It’s the workflow for which Harlequin VariData was designed, to maximize the throughput of variable data files through the Digital Front End (DFE) and onto the press.

But in some cases the variable data is not available when the job starts printing. Indeed, the print ‘job’ may run for months in situations such as packaging lines or ID card printing. That can be managed by simply sending a whole series of optimized PDF files, each one representing a few thousand or a couple of million instances of the job to be printed. But in some cases that’s simply not convenient or efficient enough.

In other workflows the data to be printed must be selected based on the item to be printed on, and that’s only known at the very last minute … or second … before the item is printed. A rather extreme example of this is in printing ID cards. In some workflows a chip or magnetic strip is programmed first. When the card is to be printed it’s obviously important that the printed information matches the data on the chip or magnetic strip, so the printing unit reads the data from one of those, uses that to select the data to be printed, and prints it … sometimes all in less than a second. In this case you could use a fully resolved optimized PDF file and select the appropriate page from it based on identifying the next product to be printed on; I know there are companies doing exactly that. But it gets cumbersome when the selection time is very short and the number of items to be printed is very large. And you also need to have all of the data available up-front, so a more dynamic solution is better.

Printing magnetic strip on ID cards
Printing magnetic strip on ID cards.

In other cases there is a need to ensure that the data to be printed is held completely securely, which usually leads to a demand that there is never a complete set of that data in a standard file format outside of the DFE for the printer itself. ID cards are an example of this use case as well.

Printing Example ID cards

Moving away from very quick or secure responses, we’ve been observing an interesting trend in the labels and packaging market as digital presses are used more widely. Printing the graphics of the design itself and adding the kind of data that’s historically been applied using coding and marking are converging. Information like serial numbers, batch numbers, competition QR Codes, even sell & use by dates are being printed at the same time as the main graphics. Add in the growing demands for traceability, for less of a need for warehousing and for more print on demand of a larger number of different versions, and there can be some real benefits in moving all of the print process quite close to the bottling/filling/labelling lines. But it doesn’t make sense to make a million page PDF file just so you can change the batch number every 42 cartons because that’s what fits on a pallet.

These use cases are why we added Dynamic overlays to Harlequin. Locations on the output where marks should be added are specified, along with the type of mark (text, barcodes and images are the most commonly used). For most marks a data source must be specified; by default we support reading from CSV files or automated counters, but an interface to a database can easily be added for specific integrations. And, of course, formatting information such as font, color, barcode symbology etc must be provided.

The ‘overlay’ in “Dynamic overlays” gives away one of the limitations of this approach, in that the variable data added using it must be on top of all the static data. But we normally recommend that you do that for fully resolved VDP submissions using something like optimized PDF anyway because it makes processing much more efficient; there aren’t that many situations where the desired visual appearance requires variable graphics behind static ones. It’s also much less of a constraint that you’d have with imprinting, where you can only knock objects like white text out of a colored fill in the static background if you are using a white ink!

For what it’s worth, Dynamic overlays also work well for imprinting or for cases where you need to print graphics of middling complexity at high quality but where there are no static graphics at all (existing coding & marking systems can handle simple graphics at low to medium quality very well). In other words, there’s no need to have a background to print the variable data as a foreground over.

So now you know why we’ve doubled up on variable data functionality!

Further reading:

  1. What’s the best effective photographic image resolution for your variable data print jobs?
  2. Why does optimization of VDP jobs matter?

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What is a Raster Image Processor (RIP)?

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.

The raster image processor pipeline. The Harlequin RIP includes native interpretation of PostScript, EPS, DCS, TIFF, JPEG, PNG and BMP as well as PDF, PDF/X and PDF/VT, so whatever workflows your target market uses, it gives accurate and predictable image output time after time.
The raster image processor pipeline. The Harlequin RIP includes native interpretation of PostScript, EPS, DCS, TIFF, JPEG, PNG and BMP as well as PDF, PDF/X and PDF/VT, so whatever workflows your target market uses, it gives accurate and predictable image output time after time.

Harlequin Host Renderer brochure

 

To find out more about the Harlequin RIP, download the latest brochure here.

 

This post was first published in June 2019.

Further reading:

1. Where is screening performed in the workflow

2. What is halftone screening?

3. Unlocking document potential


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Choosing the software to drive your digital inkjet press

When developing your first or next digital press, the software you use to drive it will be a key factor in its success, both for the data rates and output quality you can achieve. The time it takes to get your press to market based on the engineering effort involved to deliver and integrate that software is also a consideration.

A simple user interface to get  you started

The Press Operator Controller (POC) is an example front end or user interface available with Harlequin Direct™ , the software solution that drives printhead electronics at ultra-high data rates while retaining high output quality. The POC provides you with an initial working system, so you’re up and running without any significant in-house software development. We provide you with the source code so that you have the option to update and integrate it as part of your production system.

I have created a short video to show you its main functions:

You can find out more information about the Direct™ range of products by visiting our website: https://www.globalgraphics.com/products/direct

Further reading about considerations when choosing your digital inkjet press:

  1. How do I choose the right PC specification for my digital press workflow
  2. Future-proofing your digital press to cope with rising data rates
  3. Looking to reduce errors with simple job management, keep control of color, and run at ultra-high speed for jobs with variable data?

About the author

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

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How to accurately calculate the ink costs for your digital press

There are many costs that can impact your profitability when running a production digital press, from power consumption to the substrate you’re printing on. One of the most variable costs is ink consumption, which often varies from job to job and therefore can be difficult to estimate. As you might expect, the content to be printed is the key determining factor, but you also need to consider the resolution, screening method, drop sizes and choice of colorants. This can bring quite a challenge for a press shop when quoting for a job, especially if the client is open to hearing a range of options.

Even with a static job that might be suitable for a test print run to get a cost that can be multiplied for the number of copies, it’s still not ideal to have to spend any time or other resources using the actual press. It’s much better to be able to get an accurate ink cost estimate away from the press, which is where our Job Cost Estimator comes in. It’s available as part of our Direct™ software range as well as our Harlequin Host Renderer™ and ScreenPro™ products. It uses the same setup that drives your printer, calculating a very accurate estimate of the ink cost for a specific job. Self-contained, it doesn’t require any connection to your printer, which makes it ideal when you want to give a job cost indication away from the print shop.

The screenshot shows a calculation performed using our Job Cost Estimator for a 1200x1200 dpi version of our two-page Direct brochure, screened with 4-drop pearl.

The screenshot above shows a calculation performed using our Job Cost Estimator for a 1200×1200 dpi version of our two-page Direct brochure, screened with 4-drop pearl. Under Cost Per Page, this is the average cost per page per colorant based on the two pages that were analyzed, with a final row showing the total (All). This is then multiplied by the total pages and the number of copies to get the Cost Per Job for each row.

Obviously, no costs can be determined without knowing how much the inks cost per liter, so you can set these within the application. Similarly, you will need to configure your printhead(s) to specify how many picoliters of ink are used per drop size.

As you can see from the left image above, we have assigned a different printhead for Black called Budget_PrintHead, which will have fewer picoliters per drop size than the Default_PrintHead shown on the right, to represent a possible response to a hypothetical jump in the price of black ink.

The Job Cost Estimator has been designed to be extensible, so it would be possible in future to incorporate other costs, such as paper, or factor in ink used periodically for nozzle refreshing, for example.

If you’d like to know more about the Job Cost Estimator, watch my short demonstration here:

For more information visit the Direct pages on our website: globalgraphics.com/direct

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About the author:

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

Full Speed Ahead: How to make variable data PDF files that won’t slow your digital press

The use of variable data has increased exponentially over the past five years and is emerging in new applications such as industrial inkjet. Yet poorly designed variable data PDF files disrupt production and reduce ROI.

Watch the recent webinar with Global Graphics Software’s CTO Martin Bailey, the author of Full Speed Ahead, a new guide to offer advice to anyone with a stake in variable data printing, including graphic designers, print buyers, production managers, press operators, composition tool developers and users.

In the webinar Martin presents an overview of the guide and highlights some of the key tips and tricks for graphic designers, prepress and print service providers, showing how, when they all work together, VDP jobs can fly through digital presses.

Sponsored by Delphax Solutions, Digimarc, HP Indigo, HP PageWide Industrial, HYBRID Software, Kodak, Racami and WhatTheyThink, the guide is a practical format for easy reference and includes:

• Tips and tricks for making fast, efficient PDF files for variable data printing
• Helpful illustrations, photos and explanatory diagrams
• Real examples from industry

You can download your copy here: https://www.globalgraphics.com/full-speed-ahead

For further reading about PDF documents and standards:

  1. PDF Processing Steps – the next evolution in handling technical marks

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Harlequin RIP gains Ghent PDF Output Suite 5 compliancy

We’ve just added the Harlequin RIP® to the list of products certified as compliant with the Ghent Workgroup’s Output Suite 5 at https://www.gwg.org/ghent-pdf-output-suite-5-compliancy/

It was an interesting exercise, not because it was difficult, but because we started with a bit of archaeology. Back in February 2003 we published an “Application Data Sheet” of instructions for configuring versions 5.3 and 5.5 of the Harlequin RIP to render PDF/X-1a files. We followed that up with another edition for Harlequin 6 (the Eclipse release), addressing PDF/X-3 as well in 2004, and then for Harlequin 7 (Genesis) in 2005.

After that it seemed that PDF/X was sufficiently well understood and so widely adopted in the marketplace that we didn’t need to continue the series. Added to that, we’d added the ability for Harlequin RIPs to recognize PDF/X files and automatically change the RIP configuration around things like overprinting to, as we phrased it at the time, “Do the Right Thing™”.

So when we started writing up how to configure Harlequin for the GWG Output Suite we simply opened up the 2005 doc and replaced the screen grab of the user interface in Harlequin MultiRIP with a one from Harlequin 12.1. In 14 years we’ve added a few options, and, of course, a Windows 10 dialog looks a bit different to one from Windows XP!

We did have to add a couple of extra bullet points to the instructions, especially around perfecting the color management of spots being emulated in process colorants. Some of our color focus over the last decade has been on outputting to a fixed ink set, whether that’s on a digital press or for flexo or offset. So we made the point by delivering our sample output to be reviewed by the GWG as a CMYK raster file … and yes, all of the spot colors in the test suite showed up correctly in their emulations, it all passed 100%.

But that was it.

We thought about adding an indication of which RIP versions the instructions applied to, but ended up simply pointing out when a configuration item had been changed from a check-box to a three-way drop-down menu. The instructions will give you good output from all Harlequin RIPs shipped by Global Graphics in the last decade, and into the future as well.

I love it when stuff just works, and continues to just work, like this. There’s definitely a benefit to aiming to Do the Right Thing™!

Harlequin RIP® gains Ghent PDF Output Suite 5 compliancy
Harlequin RIP® gains Ghent PDF Output Suite 5 compliancy

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RIP technology replacement achieves a faster development time, performance and quality benchmarks

 VIR Softech replaces RIP software for major print OEM and achieves a faster development time, performance and quality benchmarks

When a major print OEM switched from a market-leading RIP technology to the Harlequin RIP®, they achieved a faster development time and performance and quality benchmarks with a reduced bill of materials cost.

The Challenge
When a leading print OEM was looking to move to a PDF RIP technology that was easy to integrate and help to achieve quality and performance benchmarks, it contacted Global Graphics Software Partner Network member, Vir Softech. As a RIP replacement service provider, the team at Vir Softech includes experienced engineers, with experts who have worked on all the major RIP technologies and understand the interfaces and functions they offer.

The Solution
Vir Softech recommended switching from the existing RIP technology to the Harlequin RIP from Global Graphics Software. Vir Softech had experience of using the Harlequin RIP in a similar project and knew it would meet the print OEM’s requirements. After a period of evaluation, including quality and performance benchmarking, the print OEM chose to use the Harlequin RIP.

Deepak Garg, managing director at Vir Softech explains the process: “The first step towards making the change was to assess and understand the various features and functions offered by the OEM’s print devices.”

After investigating, the team prepared a design document highlighting:

  • The OEM’s product features that interact with the RIP technology
  • How these product features are implemented
  • The various RIP interfaces which are used to implement these features and functions

Deepak continues: “Once the print OEM decided to go ahead, we prepared another document highlighting how to achieve these functions using the Harlequin interfaces. Some functions or features could not be implemented using Harlequin directly, such as special color handling, spot color replacement, extraction of cut data etc., so we contacted Global Graphics Software who was able to provide a design showing how these functions could be implemented using Harlequin. We then prepared a proof-of-concept, or working implementation, which demonstrated how the Harlequin RIP would work with the print OEM’s print devices. With Harlequin, such a prototype can usually be achieved within three to six months.”

The Result
Development time was much shorter than usual for such an ambitious undertaking, greatly reducing costs and enabling the print OEM to drive their revenue earlier than originally expected. The print OEM began using the Harlequin RIP, instantly meeting its quality and performance targets.

The print OEM says: “The Harlequin RIP helped us to move to native PDF printing and achieve the performance targets for our printers. Harlequin also helped us to reduce the lead time for getting our products to market while keeping development and maintenance costs low.”

About Vir Softech
Vir Softech is a technology start-up with expertise in imaging and computer vision technologies. With a strong focus in the Print & Publishing domain, its team of experienced engineers includes experts in all aspects of imaging and RIP technologies, such as job management, job settings, color management, screening, bands generation and management, VDP and imposition etc.

The team at Vir Softech are experts in configuring RIP technologies for better performance targeted for a specific market segment such as production, commercial, large format and enterprise printing. Some of the areas where Vir Softech can help include low resource environment, implementing OEM-specific unique functions using Harlequin RIP interfaces, making use of OEM ASIC for better performance, making use of OEM hardware accelerators for some of the computer-intensive RIP operations such as color conversion, image transformations, image decoding, rendering etc and achieving PPM target of MFP for ISO test suites.

To find out more visit: www.virsoftech.com

 

 

 

New Flexo screens give premium print quality

HXMFlexo screens
Bump up curves in Harlequin’s new flexo screens help pre-press operators achieve smooth gradations even in high-key images.

Our Harlequin product team has launched a set of hybrid screens specially developed to give premium quality in flexo work.

The screens address the well-known issues of how to achieve high-quality in the highlight areas of images, such as tones close to white or skin tones, and how to print those areas with smooth gradations.

“We used the Harlequin Cross Modulated™ screens as the basis for development and have expanded the number of screens and included a mechanism to auto select calibration that goes with a particular screen,” comments Martin Bailey, CTO, Global Graphics.

“With the new Harlequin Cross Modulated Flexo (HXMFlexo) screens you can produce high-quality graphical objects by selecting from a wide choice of screen resolutions, rulings and dot sizes. Pre-press operators also now have the ability to bump up curves at the highlight end to compensate for flexo not being able to produce tones close to white clearly, so you can achieve smooth gradations even in high-key images.”

The new screens are the result of working with our OEM partners in the flexo market who have used the Harlequin RIP for years and we’ve been able to take input from a variety of vendors to fine tune our plans.

HXMFlexo works with the latest editions of the Harlequin RIP.