textiles – Global Graphics Software blog

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:

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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

Martin Bailey, CTO, Global Graphics Software

Recently my wife came home from a local sewing shop proudly waving a large piece of material, which turned out to be a “swatch book” for quilting fabrics. She now has it pinned up on the wall of her hobby room.

It made me wonder how many separations or spot colors I’d ever seen in a single job myself … ignoring jobs specifically designed as swatches.

I think my personal experience probably tops out at around 18 colors, which was for a design guide for a fuel company’s forecourts after a major redesign of their branding. It was a bit like a US banknote: lots of colors, but most of them green!

But I do occasionally hear about cases where a print company or converter, especially in packaging, is looking to buy a new digital press. I’m told it’s common for them to impose together all of their most challenging jobs on the grounds that if the new press (or rather, the DFE on the new press) can handle that, then they can be confident that it’ll handle any of the jobs they receive individually. Of course, if you gang together multiple unrelated jobs, each of which uses multiple spot colors, then you can end up with quite a few different ones on the whole sheet.

“Why does this matter?” I hear you ask.

It would be easy to assume that a request for a spot color in the incoming PDF file for a job is very ephemeral; that it’s immediately converted into an appropriate set of process colors to emulate that spot on the press. Several years ago, in the time of PostScript, and for PDF prior to version 1.4, you could do that. But the advent of live transparency in PDF made things a bit harder. If you naïvely transform spots to process builds as soon as you see them, and if the spot colored object is involved in any transparency blending, then you’ll get a result that looks very different to the same job being printed on a press that actually has an ink for that spot color. In other words, prints from your digital press might not match a print from a flexo press, which is definitely not a good place to be!

So in practice, the RIP needs to retain the spot as a spot until all of the transparency blending and composition has been done, and can only merge it into the process separations afterwards. And that goes for all of the spots in the job, however many of them there are.

Although I was a bit dismissive of swatches above, those are also important. Who would want to buy a wide format printer, or a printer for textiles, or even for packaging or labels, if you can’t provide swatches to your customers and to their designers?

All of this really came into focus for me because, until recently, the Harlequin RIP could only manage 250 spots per page. That sounds a lot, but wasn’t enough for some of our customers. In response to their requests we’ve just delivered a new revision to our OEM partners that can handle a little over 8000 spots per page. I’m hoping that will be enough for a while!

If you decide to take that as a challenge, I’d love to see what you print with it!

Tag: textiles

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

Channelling how many spot colors?!!