One of the greatest advantages of direct-to-substrate digital printing is it allows you to offer a comparable product without the trial-and-error learning curve associated with screen printing. Set-up is much faster, printing is easier and, for certain types of jobs, it’s more profitable. Still, creating top-notch garments with a digital printer isn’t without its challenges, and the trick to overcoming these is to follow a few simple guidelines on what to do.
It’s all about artwork
Perhaps the most important “trick” to getting great-looking images from your digital printer is simply to understand the fundamentals of artwork for decorated apparel. In fact, most newcomers’ questions and issues regarding direct-to-substrate printing have more to do with artwork than with the equipment or digital-printing process itself. They ask, for instance: “What kind of files should I use? How do I edit these files? How do I change my image’s color?”
The best suggestion for anyone struggling with such issues is to become familiar with graphics software—primarily Adobe Photoshop, which is perhaps the most versatile, flexible program for designers, and one of the most widely used in the industry. The program has a relatively short learning curve, and your supplier can help you master Photoshop’s basic functions such as color correction and photo resizing.
You can open almost any graphic file in Photoshop and, for example, view its resolution (dots per inch, or dpi). While 300 dpi is ideal for digital printing, you can get away with 150 dpi if you have a quality image and you’re printing it smaller than the original size. If you have, say, a 10” X 20” image at 150 dpi and you print it at only 2” X 4” the results should look fine.
Because it is so important to have a firm understanding of graphics software, and artwork in general, you should consider formal training. Numerous industry suppliers offer training on artwork, and, naturally, you’ll find countless forums and webinars online that may prove helpful in your artwork education.
Speaking of artwork, certain direct-to-substrate printers allow you to resize images on the fly, as well as change image location, speed up or slow down the machine, increase or decrease ink density. Changes like these aren’t actually handled in a program such as Photoshop; they’re handled using the software that comes with the digital printer. And, naturally, you’ll want to get plenty of training from the supplier on how to use these proprietary programs.
Another common area of concern from users is that the machine’s heads and nozzles will dry out and clog. While all digital printers are subject to clogged heads and nozzle failures, the reality is you can greatly decrease or eliminate this problem if you run the machine frequently.
When a digital printer sits idle for too long, ink settles in the heads rendering them unable to fire properly. This generally isn’t a problem with CMYK inks, but monitor the white ink carefully to prevent clogging. Some manufacturers require that you shake the white ink before you print and when you’re done to keep the sediment from settling and clogging the heads; others require you to shake it only once.
Clogging can also result from a print head coming into contact with a pretreated garment. The main purpose of pretreatment is to act as a barrier to keep the ink from sinking into the shirt; apply this characteristic to an inkjet head, and the results are obvious. Leaving the cap off the heads overnight and exposed to air can also lead to clogging, as can using an ink other than the one recommended by your machine’s manufacturer.
It’s important to make sure the unit’s heads are a suitable distance from the substrate. Some direct-to-substrate printers have automatic height adjustment, meaning that when you load a new substrate, the machine automatically calibrates itself so that the head is at the optimum height for printing.
If your machine doesn’t have such a feature, be sure to perform the adjustment manually, lest the heads get damaged by coming into physical contact with the substrate. You certainly don’t want to find yourself shopping for new inkjet heads—at $1,000 to $3,000 a pop—just because a sweatshirt’s zipper was too close and damaged them. Otherwise, assuming you run your machine regularly and subject it only to normal wear and tear, you can expect your inkjet heads to last anywhere from five to 12 years.
You’ll rarely, if ever, have color reproduction issues on white T-shirts. But you may have some color fluctuation on dark garments, which require pretreatment and a white underbase. The solution? Suppliers offer color books with the CMYK “recipe” listed for each color. If you need Pantone 185 Red, for example, you would input the color value, or recipe, from your color book.
As for the underbase, the best way to create it is using Photoshop, with halftones that fade into the shirt. Alternately, nearly every entry-level printer has RIP software or a printer/driver that automatically generates a white underbase for you.
You’ll want to apply pretreatment spray as consistently as possible to ensure high-quality images on garments. If you have inconsistent coverage or don’t apply enough, the result can be a white underbase that doesn’t provide sufficient coverage, as well as problems with bleeding. Inks with extremely low opacity also can cause bleeding. If you’re struggling with bleeding problems and you are sure you’re applying enough pretreatment, try printing the white underbase two or even three times.
Blurring can be a problem. Newcomers to direct-to-substrate printing sometimes find that their artwork looks blurry, a problem that’s usually the result of a low-resolution image or an inkjet head set at the wrong height.
As for dirty prints, lint from garments and other dirt have a tendency to collect around the machine’s head––in part because the ink is moist––causing a gooey buildup. Keep your equipment clean by wiping it with a lint-free rag at least once a day and at the end of longer production runs. Be sure to use the clean surface of the rag, and don’t use a paper towel, which can leave fibers in the nozzles. You can also moisten a lint-free rag with purified water or solution provided by your supplier, but don’t use any acetone- or solvent-based cleaners.
When your machine’s indicator shows it is low on ink, go ahead and add new ink rather than waiting until you’re totally empty. Running the cartridge completely empty can introduce air into the system. Any money you save by waiting to replace the ink will be offset by the additional time and ink you’ll use to get the air out of the system. Of course, if you’re using a bulk system instead of a cartridge system, this isn’t an issue, as you’ll simply add ink to the machine’s containers. However, some decorators prefer the convenience of a cartridge-based system.
Undercuring a digitally printed garment causes the same kinds of problems you’ll see with an under-cured screen-printed garment: cracking and lifting of the ink off the shirt. One way to anticipate this problem is to wash-test a few garments before printing them in bulk. Another option is to perform a stress test: Hold the fabric between your thumb and finger, and stretch it vertically and horizontally—if the image cracks, it’s probably not cured.
Your machine’s RIP software has preset color profiles that set the CMYK and white output levels for a particular resolution or garment type. If you’re unhappy with your machine’s stock profiles, talk to your supplier about custom ones, such as profiles with higher ink densities.