are several basic types of pad printing machines.
The majority of machines in use around the industry
are referred to as vertical machines. These
machines can be open or closed. In closed systems
doctoring is achieved by either sliding the
ink cup back and forth over the cliche' surface,
or by sliding the cliche' beneath a stationary
ink cup. The illustration below shows a typical
vertical machine with an ink cup.
Some vertical machines can print on any angle using a special
pressurized ink cup. Instead of using gravity
to flood the cliche', pressurized ink cups use
an inflated diaphragm to ensure the image is
properly flooded. Pressurized ink cups can be
difficult to install and maintain. The illustration
to the right shows how a pressurized ink cup
Closed vertical machines have
also been modified so that their ink cups slide
along the X-axis, allowing the printing of wider
images. This type of machine is commonly referred
to as a "sliding ink cup" machine. The illustration
below shows this variation.
delaying the pad at the end of the print stroke
some vertical machines can print 360 degrees
around a cylindrical object. The image is transferred
as a gear driven nest rolls the part along the
length of the pad. The illustration to the right
shows how this works.
Without any special pad delays or gear driven
nesting fixtures vertical machines can print
a maximum of 120 degrees on a cylindrical object.
To accomplish this, the pad's set-down point
must be top, dead center. The pad is then compressed
60 degrees in each direction from the set-down
Horizontal pad printers are really
just another variation of vertical machines.
Horizontal machines flood and doctor like vertical
machines, then actuate the pad to print using
a horizontal stroke, rather than a vertical
one. The illustration on the following page
shows a typical horizontal pad printer.
Horizontal machines are typically used only
when the part is too large to fit into a vertical
machine, or when the image is too large to fit
into a pressurized ink cup.
Rotary pad printing machines are
very different from their vertical and horizontal
counterparts. Rotary machines have cylindrical
cliché’s, usually referred to as "drums". The
cliché’s are flooded and doctored as they rotate.
The pad also rotates to pick up and transfer
Rotary pad printers can be configured to print
vertically or horizontally. Vertical machines
can be self-standing for one-up printing, or
mounted on automations for tandem or multiple
color printing. The illustration below shows
a basic vertical rotary design.
Horizontal rotary pad printers
are used to print on the vertical sides of parts
that are moving along a conveyor. The following
illustration is an example of how cassette tapes
would be printed on two sides at once using
a horizontal rotary pad printer.
Carousel machines allow a part
to be printed with multiple colors without ever
being moved. Ink cups and cliché’s are mounted
on a rotary indexing table which turns to locate
each individual cliche' under rotating pads
for image pickup. The pads then rotate around
on a separate carousel, locating over and compressing
onto the part to be printed. These machines
are typically slower than their multiple color,
standard vertical counterparts, and are used
only for printing parts too large to fit a standard
Pad printing machines are driven by a number
of different means. Most machines are driven
by electronically controlled pneumatic systems
and are thus referred to as being electro-pneumatic.
Some pneumatic machines are controlled by air-logic
instead of electronics. Less expensive than
electro-pneumatic machines, these can be more
difficult to control, especially if your incoming
air pressure isn't well regulated.
Electro-mechanical machines operate under electrical
power only. These machines are usually more
expensive than electronically controlled pneumatic
machines. They can hold tight tolerances, even
at high cycle speeds.
Electro-hydraulic machines are the most expensive
type. These machines are rare, and are typically
used only for large format applications where
additional compression is necessary.
Manually operated machines are useful for small
format and short run applications. Images are
usually limited to less than 16 square inches,
and multiple color printing capability is limited.
Many manufacturers of manual machines offer
trade in allowances when upgrading to semiautomatic