Screen Sept 09 P8-9:Page 6 21/09/2009 14:56 Page 9
SCREEN
polypropylene and polyethylene are partially screen printing still remains the most cost
crystalline. Where ultrasonic welding is not effective solution. For short runs digital
suitable heat, in the form of hot air or printing has to be the best bet. Print and cut
conduction using contact, can be extremely increases the viability of digital printing as an
effective. Polyethylene is ideally suited to additional finishing process is removed. Hot
hot air welding. foil blocking and even heat applied transfers
are also used extensively.
Get the message It seems that the market is becoming less
No matter what process is used for pro or anti digital and screen and the
joining, staking or forming, combination of various processes can provide
manufacturers are still faced with very attractive effects. Innovative design will
the task of printing the message entice purchasers into buying added value
onto the substrate. Screen products to everyone’s benefit. Those
printing continues to cover practitioners who can select the most suitable
most if not all of the printing method for the particular application
applications. Of course if are the ones who succeed. Sometimes it can
images are four colour be rather like trying to put a nail in with a
process then the line screwdriver or a screw with a mallet. Using
ruling of a print that the wrong process is the way to burn money
is viewed within fast.
arms length
should Working in harmony
ideally be With this sector of the market the printing
better processes used are just part of the overall
product offering. They have to work in
combination with other operations. Normally
the plastic substrate, be it PVC, polyethylene
or polypropylene, is printed before it is
assembled into the finished product. On
occasions however, items that have
already been produced are printed in
their finished form.
This is where pad printing
comes to the fore. The item
may be too uneven to
screen print, too delicate
to foil block or too
awkward to print on a flat
bed digital printing
If the volume is large and fine resolution is machine. Pad printing requires
required, lithographic printing is the answer limited capital investment but has the
capability to print a wide range of substrates
and designs.
Visiting some of the UK's sub-contract
than 80 printing companies demonstrates the
lines per inch, versatility of the various processes in the
preferably over 100 hands of experts. Much of the equipment may
lines per inch. This is where be twenty years old but still earning good
the marriage of digital and screen money for the company. That's because there
Users of PVC in this industry aim to use as technologies can be perfect. If, however, the is no substitute for experience and the ability
much recycled material as possible. volume is large and fine resolution is required, to adapt equipment and methods to suit a
Polypropylene is used wherever it is suitable. lithographic printing can take over. particular application. Practical skills like this,
Much of the fabrication of binders, place Producing the product after the substrate is namely the ability to design, build and
mats and plastic goods is done by ultrasonic finished and formed is where the skill and operate solutions to practical problems, are
welding. This uses the vibrations set up in the added value lies. If the application is simply line the backbone of industrial
process to weld two similar plastics together. colour and particular Pantone matches, then development. a71a71a71a71
For best results, the two plastics will be
identical. Sound is generated that cannot be
heard by the human ear and this is
concentrated through a device known as a
horn. The vibrating horn is brought into
contact with two pieces of plastic, one on top
of the other, and the vibrations created
between the two surfaces cause them to melt
and fuse together. This fusing process will only
work when the plastic is amorphous rather Combining various
than crystalline. ABS, acrylic, polycarbonate processes can provide
and PVC are amorphous, whereas attractive effects
Visit us at www.spdi-online.com September 2009 l SCREEN PROCESS AND DIGITAL IMAGING 9
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