Multiple color capability is probably the most popular option. Obtaining
this capability can be as easy as purchasing
a multiple color (split) ink cup or cliche'
holder, or as difficult as completely retrofitting
an existing machine.
A few manufacturers offer small (60.0 mm) two
or three color, split ink cups. These cups allow
you to print multiple color side by side, or
in some cases wet on wet. The limitation is
size versus cost, as these cups are very expensive.
I have seen a two color ink cup that costs $1,800.
Multiple color inkwells can allow you
to switch from one to as many as four colors
in open systems. In addition you would also
need a set of multiple color accessories, like
an ink spreader, doctor blade assembly, and
Most multiple color systems are designed
as such, rather than modified into being. In
open systems for example, it is better to have
four independently adjustable cliché holders
than one multiple color ink well, as artwork
and cliche' layout, and machine set-up is much
easier when you have the additional adjustability.
The same holds true to multiple colored closed
systems. Having two, three, four or six
independently adjustable cliché’s is much better
than trying to put several images on one cliche'.
Having semi-automatic or automatic multiple
color capability requires a method for moving
the parts from color to color without changing
nests. (It is not recommended that you print
one color, then move the part to another nesting
fixture for subsequent prints.)
This can be accomplished by means of a part
shuttle, a rotary indexing table, or a conveyor
of some type.
Part shuttles can be pneumatic, or electronic.
Electronic shuttles are more expensive than
pneumatic ones, but last longer and are typically
more accurate. The nice thing about either one
of these two options is that you only need to
build one nesting fixture.
Rotary indexing tables can be either
electronic or pneumatic as well. Here again,
the more expensive electronic versions offer
better accuracy and durability. Some manufacturers
stock modular rotary systems that allow you
to use up to four machines either simultaneously
or individually. The number of nesting fixtures
needed depends upon the size of the rotary table
and the parts you're printing.
Conveyors can be "racetrack" or "over-under"
type conveyors. Racetracks are usually pneumatically
driven. Many times these are standard equipment
on multiple color machines. Over-under conveyors
are less popular. Operating like an oval shaped
paddle wheel, these conveyors require that the
parts be dried prior to falling off their nests
at the end of the line.
Drying parts is as easy as attaching
a hot-air dryer to the outbound side of the
printer on a rotary indexing table or conveyor,
or by having a separate self-standing tunnel
dryer like those used in the screen printing
One process limitation that I mentioned was
the requirement that the substrate have a higher
surface energy than the pad. Certain low surface
energy materials can be pre-treated to increase
Pre-treatment can be accomplished using
flame treating, corona treating or plasma treating
Flame treating is the most popular method.
The equipment uses specially designed flame
treating heads to carefully control the amount
of surface treatment. Since heat can cause damage
to some materials, flame treatment is not always
Corona and plasma treating equipment
both use electricity to deposit an ion rich
discharge on the surface of the substrate. Corona
is more useful on large, flat parts, whereas
plasma is more useful on smaller, three-dimensional
Ink pumps and thinner metering devices
are used to control ink viscosity during long
production runs. Ink pumps are used to add thinner
to the ink in open, recirculating systems. Thinner
metering devices are used to add thinner to
closed ink cups.
Ink residue removal systems or "tape-offs"
are used for cleaning ink and debris off
of the pad surface during the print cycle. Using
a slide mechanism, these systems position an
adhesive covered "tray" beneath the pad after
a print stroke. The pad is then compressed onto
the tray where the adhesive removes ink and
debris. The tray then retracts, and printing
Nesting fixtures are many times taken
for granted. Until you gain a knowledge of pad-print-specific
requirements with regard to designing and building
nesting fixtures it is highly recommended that
you allow the pad printing equipment manufacturer
to build your nests.
Pad shuttles are an option useful in certain
applications where your ink cup or cliche' isn't
large enough for the image you want to print,
and you don't want to buy a larger machine.
Safety equipment other than that which
comes standard is an option you may want the
pad printing equipment manufacturer's advice
on. I have seen a number of perfectly good machines
rendered almost useless by the addition of poorly
designed safety enclosures and / or equipment.
The people who design and build pad-printing
equipment know what is practical, and what is
More Information on
contracting a Pad Printer