By Jamie Swedberg
When fabricators use wide- or grand-format digitally printed fabrics to create structures such as tents, awnings and large graphic displays, precision finishing is the name of the game. Some printed fabrics must slide perfectly into silicone edge graphic frames without distorting or sagging. Others must be seamed, with edges perfectly aligned, into finished products that are 100 feet long or more.
“One time we direct-printed on army duck tent fabric,” relates Scott Powell, marketing director at Rainier Industries, Tukwila, Wash. “When we finished it, we were an inch shorter in width and an inch and some change less in length. Nobody realized that until we put the poles in, and they didn’t fit.”
What did they do? “We cut the poles,” laughs Powell. “Luckily, it was in a situation where it wouldn’t matter. But, you know, you will have these issues that you have to deal with. You’re dealing with fabric, and you’re stretching it and you’re adding ink to it and you’re heating it. Your tolerances, depending on the fabric, can be quite… well, unpredictable is the wrong word, but they aren’t always spot-on.”
Here are five guiding principles for better finishing of wide-format printed fabrics. Fabricators who follow these guidelines will find that their end products are better-looking and longer-lasting, and that their customers are more satisfied.
1. Good finishing starts before the fabric is ever printed
Just about everyone who owns a wide-format printer understands the concept of profiling, but it bears mentioning again, considering that more and more fabrics are considered printable. Your RIP (raster image processing) software can correct for the characteristics of a wide variety of substrates, but it cannot do so without a fabric-specific profile. You must construct a profile for every single individual fabric you use, or acquire reliable profile information from your media, printer, or ink vendors.
“First of all the ink will bleed like hell, then you’ve got to stop it from bleeding,” says Paul McGovern, national sales manager at Mimaki USA Inc. “Then when you get these little beautiful color blocks down, you can adjust the color to match your Pantone chart. Once you have that done, you control how many passes you make with the inks, you control the drop sizes you put down, and how many times you overprint. Maybe you do four pass, eight pass, sixteen, thirty-two. And that’s going to control the amount of color a particular fabric absorbs.”
But that’s not all your RIP software can do. It can also merge all of your finishing information into a series of related files for a given project.
“For example, in ErgoSoft, which is a popular RIP software, there’s a tiling option in there,” says Shane Hueit, southeast sales engineer at Mutoh America Inc. “So you can say, ‘In between each tile, I need to make a bleed-over of like an inch, or half an inch, so that I can sew right down between.’ If the print is 54 inches wide and you need to make something that’s 10 feet wide, you can put it in there—how much [extra] you need to make to allow for tiling.”
“That’s all built into the RIP in our world,” agrees Powell. “We’ve got an image file, and then we’ve got what we call a cut file that puts dots on there, so that i-cut® on the Zund [digital cutting table] can read the dots and knows how to cut the fabric. That’s where it all happens.”
Powell says where it makes sense to do so, his company’s designers also include dots in the files to indicate grommet placement so that the grommet machine operators can just “pull to the dots and step.” That means better precision, which can improve the look and performance of the end product.
David Segal, president of Edward Segal, Thomaston, Conn., says this is a common strategy. “Some will put a little dot along the border where they want the grommets to be, to help the operator find that position,” he says. “Other people will use a gauge of some sort that we provide with the machines, that allows them to space the grommets every 12 or 24 inches. They want it to have that symmetrical look.”
2. Printing may affect product performance
Mimaki’s Paul McGovern says his company’s workshop has had some recent breakthroughs. They’ve been able to use dye-sublimation to print solution-dyed acrylic fabrics right through the waterproof and UV-protectant coatings. But they’re not sure, just yet, what that will mean for the durability of the end product. Will the coatings still protect as they were intended to? Only testing will tell.
That’s going to be the case for just about any substrate that you digitally print in your shop. Not all of the end products will have the characteristics of the original fabric.
“If you’re not afraid to break one of your pieces of equipment by having something go weird, the sky’s the limit on what fabrics you can print,” chuckles Powell. “But when you use inks or fabrics you’re not really supposed to use, sometimes they can be easily scratched. That canvas tent example? The customer liked the look, but we warned them that if their people rubbed the print, it would abrade. They were okay with it.”
McGovern says his machines can print vinyl for interior marine applications, but not outdoor ones, since the sun and spray can “really tear up an ink.” But even indoors, there are caveats.
“DEET in mosquito repellent and PABA in suntan lotion can eat into your inks and fade it or destroy it,” he says. “Actually, besides just the ink, it will damage the vinyl.”
3. Specialized equipment can make it easier
John Evans, vice president of sales–graphic media at Herculite Products Inc., York, Penn., says the biggest difference between using graphics-enhanced fabrics versus plain dyed ones is that your finishing must not affect the text or image you’re trying to convey.
“If you and I are doing a tarp or a cover, whether we overlap the seam an inch or two inches, it doesn’t really matter,” he says. “No one’s going to see that. But it makes a huge difference if, at the right end of a banner promoting a 5k run, we cut off the date or time. That’s huge.”
Even tiny mistakes can mean, for example, that the two halves of a person’s face might not match up perfectly. The human eye can spot mere millimeters of error in these situations. An experienced operator can get it right, but many companies like to use some method of stabilizing the fabric while joining it.
“If you want to be able to align an image, and that’s something that you do often, we make a machine that makes that easier for the customer,” says Truy Pham, sales representative at Miller Weldmaster, Navarre, Ohio. “The 112 Extreme is a vacuum position system. The bottom panel is laid on the vacuum track, we hit a switch, and it holds the bottom in place. What that allows the operator to do is, then at that point, the machine really lines up the image so that your image isn’t shifted whenever you’re looking to put somebody’s face together, or text together. Your customer just simply won’t like it if your image is off.”
The flip side of the wide-format finishing issue is that all that fabric can be extremely heavy and unwieldy, and it can be difficult for some operators to drag the project through a stationary machine. For these situations, Segal suggests a portable grommeting machine.
“You really have two choices,” he says. “You bring the material to the machine, or you bring the machine to the material. The bigger these products get to be, the harder it is to bring the material to the machine. So we offer a portable version of a press that a lot of our large-format customers use, so that you can move it around. Everything’s got to be operator-friendly. You have to envision that a lot of these shops, their operators aren’t there for a long period of time. So the less training that’s involved in bringing a new operator in, the more efficiently they can operate.”
4. Sometimes, only experience will do
And yet, given the malleable nature of fabrics—especially knitted and woven ones—technology only goes so far. You’d think that between advanced RIP software and a digital cutting table, you could delegate the job to trained seals, but that couldn’t be farther from the truth. It is an art.
“The only way any of these big [printers] deal with fabric is that you create tension by holding the roll that the fabric’s on and creating tension with the front pull roller,” says Powell. “We have to put in factors to allow for the fact that we’re over-stretching it, printing it, over-stretching it, cutting it, and then when it pops back, we need it to be fairly precise.”
Powell says that with experience, his shop has developed a series of formulas for all the fabrics it works on. But there’s still the sewing process to take into account.
“Especially when the fabric is stretchable; the seams, as hard as you try, are never perfectly straight,” he says. “But it’s what I call craft sewing, as opposed to just hemming banners. We’ve got people who have been doing this for 15 or 20 years, who make it work.”
5. Getting into the game can be costly
The final principle of finishing wide-format fabrics is that to do it well is as expensive as acquiring the printer in the first place. It’s a competitive business, says Powell, and right now you need to have a 10-foot-wide printer to be competitive in the fabric market. Unfortunately, he says, that generally means you have to buy a 10-foot-wide cutter to go with it. For every size increase on the printing end of the process, one must also occur at the cutting end, and possibly on other finishing equipment as well. And in addition to the up-front cost of the machinery, there’s also the practical issue of where to put the equipment in a shop with limited space.
Some people might say you can cut these printed fabrics by hand, but Powell respectfully disagrees.
“It’s the precision, the squareness, the speed and quality of the cut,” he says. “You’re not going to have a competitive product at the end-customer level if you don’t have automated cutting. That’s my philosophy.”