psi – jet of water, or a mixture of
water and an abrasive material, to cut
fabric, as well as leather and plastic
materials.
A stitch in time
Another fi nishing process is sewing,
and the specifi c type of sewing will
vary according to the fi nal product
you’re making. If the fabric is going to
be made into a garment, it will need to
be sewn according to the pattern that
was drawn up prior to printing.
If it’s going to be a banner or some
other kind of display graphics, it will
need to be hemmed. Hemming is done
to prevent the fabric from fraying (see
above), although if you use a heated
knife to seal the edges of cut polyesters,
you may be able to skip hemming. (If
you are printing and fi nishing natural
fabrics, you probably can’t avoid
hemming.) Hemming also provides
reinforcement and structural support.
Hemming can be performed by
hand, just as you would hem a pair of
trousers, although that’s not the most
effi cient process. If you are doing more
than the occasional one-off textile
banner or sign, you will need to invest
in sewing equipment, and equipment
that is more compatible with industrial
production than the Singer sewing machine
you might have at home. Fabrics
used for sign and display graphics can
be too thick for consumer
grade sewing
equipment, which
simply doesn’t have
the horsepower and
lacks the durability
that will be required.
By the way, if all
you are doing is
simple hemming, you
may not need sewing
equipment at all.
Th e easiest and least
expensive way to hem
a graphic is with double
sided adhesive
Welding systems such as Miller Weldmaster’s T3 hot wedge welding
machine can produce all the seams required for banners, signs, awnings,
and other products.
tape, aka heavy-duty
banner tape. Dedicated banner tape is
stronger and more durable than what
you would be likely to pick up in Staples.
Although tape is more commonly
used to hem vinyl banners, it can be
used on fabrics, although it’s not always
the best option since tape doesn’t stick
particularly securely to textiles. If you
are doing outdoor applications, for
example, even the slightest wind or rain
could cause the tape to come off .
Sewing equipment is not just for hemming,
but also to tile multiple panels for
extremely large signage, as well as form
pole pockets or otherwise reinforce
whatever mounting mechanism is
going to be used.
“Th ere are hundreds of diff erent
types of sewing machines, with
thousands of diff erent features,
from small home machines to
large, fully automated robotic
sewing operations and process
lines,” says Martin. “I would advise
fi nding a sewing machine supplier
that understands the industry that
you are in.”
Weld done
Remember how we used a hot
knife or a laser to cut and melt the
edges of polyester fabrics to prevent
fraying? Th e same principle can be
applied to hemming. Called welding,
the process applies heat and
pressure to fuse the fabric to itself.
Welding has more nuances than
you would think, and there are
several diff erent varieties of welding:
• Dielectric welding: Th e fabric is
sandwiched between a die and a base
plate; heat is applied and fuses the fabric
along the surface of the die.
• Rotary welding: Th e fabric is rolled
beneath wheels that apply heat as well
as pressure.
• Wedge welding: A variety of rotary
welding that uses metal wedges to apply
heat to the fabric just before it passes
beneath the drive wheels.
• Hot air welding: Another variety of
rotary welding that jets hot air onto the
fabric just before it hits the drive wheel.
Th e specifi c type of welding equipment
you buy will be a function of
the kind of material you’re trying to
weld and the products you’re trying
to make. Also be aware that welding
is not useful for natural fi bers, since
they don’t melt when exposed to heat
and pressure.
Finishing up
Keep in mind that if you’re new to fabric
printing, you can certainly choose to
outsource any or all of these fi nishing
processes. Forming alliances with
companies that specialize in textile
fi nishing can be a great way to get your
feet wet, without a great deal of initial
investment. Th en, as you get more
profi cient, you can bring the needed
processes in-house.
Next month, in our fi nal fabric-printing
installment, we’ll look at the various
vertical markets for textile printing.
An alternative to silicone-edge graphics eliminates the
need to sew a gasket onto the graphic. At the ISA Sign
Expo, SignComp was demonstrating a system in which
the fabric could be simply inserted — sans gasket —
into the frame.
PrintingNewscom June 2017 Wide-Format & Signage 23
