Key concerns in digital fabric printing

By Lily Hunter and Michael Sanders

The printing of fabrics has seen a revolution in recent years with the advent of digital technology, which has saved significant time, money and labour compared to the days of screenprinting. While the earliest digital fabric printers could process 8.2 m (9 yd) in a day, making them suitable only for prototyping purposes, today’s large-format dye sublimation presses can meet growing customer demand for the on-demand production of customized soft signage applications, ranging from flags and banners to lightboxes.

Construction and finishing

Circular and woven knits are mostly intended for apparel, as well as home furnishings.

Circular and woven knits are mostly intended for apparel, as well as home furnishings.

There are several types of fabric constructions. Circular and woven knits are mostly intended for apparel and home furnishings. While some woven fabrics are ideal for soft signage applications, the industry relies primarily on warp knits, as they offer the greatest dimensional stability.

A warp knit uses a locking stitch to provide this stability, which helps ensure a single rip in the fabric will not easily extend all the way across it. Further, a dimensionally stable fabric will not sway or torque too much after it is installed in a frame or lightbox, so the graphics should remain easily readable.

Similarly, larger air holes in the fabric are preferable, as they allow wind to pass through a banner. This in addition to the lighter weight of fabric compared to polyvinyl chloride (PVC) means soft signage is a safer option, less likely to fall on anyone.

Beyond the initial construction of a fabric, finishing also plays an important role. With soft signage applications in mind, some of the most popular after-knitting finishes for fabrics include flame retardant (FR) and durable water repel (DWR) treatments.

Not all finishes are applied in the same way, however, and so there are varying levels of effectiveness. It is worthwhile to check how a fabric’s finish has been implemented and how long it will last.

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The most durable FR treatments, for example, are accomplished by staining the yarns before they are even woven. The resulting fabrics are more expensive than alternatives, but will provide a lifetime of protection against burning. Also, they can be washed without reducing their effectiveness, which is not the case with fabrics carrying lower levels of FR protection.

Most professionals look for the American Society for Testing and Materials’ (ASTM’s) E84 standard for FR.

Customized soft signage applications range from flags and banners to lightboxes.

Customized soft signage applications range from flags and banners to lightboxes.

Performance testing

Fabrics are tested for weight, shrinkage, washability, strength, torquing, snagging, air permeability, crock (i.e. how well dyes or inks remain on the material), moisture resistance, colour migration and elasticity. When selecting fabrics, signmakers should be cognizant of which of these attributes are most relevant to their applications.

Elasticity, for example, has become particularly important due to the industry’s increased use of silicone edge graphic (SEG) frames, which make printed graphics easier to install and change out as desired. Only a stretchable fabric can be fit property into such a frame, with the right level of tension, and not exhibit unwanted wavy lines across its graphics. Equal stretch is desirable in all directions.

While sophisticated machines can allow manufacturers to fabricate very high-quality fabrics for the sign industry, it is important to keep in mind no roll is 100 per cent perfect. Further, not all fabrics behave the same way in the printing process. Whenever a sign shop switches materials, it will also need to switch its printing profiles for the intended application. Fabric manufacturers might even buy their own yarns from different sources over time, which can affect the consistency of their products.

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