PARAM'S
PRINTING PADS
Pads are three-dimensional objects typically molded of silicone
rubber. They function as a transfer vehicle, picking up ink from the printing
plate, and transferring ink to the part (substrate). They vary in shape and hardness
depending upon the application.
Five key pad characteristics can affect
the quality of the printed image:
1. Design and shape
2. Size
3.
Hardness
4. Super surface finish
5. height of the pad
6. Quality of material
If
you vary any one of these characteristics , the print quality will change. You
must take these points into account when you plan the job and order pads from
your suppliers.
Shape is the most important variable in selecting a pad. Four
basic shapes are as follows:
» | Round(conical
also) | » | Rectangular/square | » | Bar(tapered
or half rounds) | » | V-shaped |
At
PARAM INTERNATIONAL Although hundreds of pad shapes are available, most are based
on these Four shapes: round, rectangular, bar shaped or v-shaped. Regardless of
what pad shape you choose for a job. For best printing results use the largest
pad size that is practical for the item to be printed.
Try to avoid flat-bottomed
pads , as they have a tendency to trap air when they come in contact with the
cliche , hampering ink pickup.
Another important variable to consider is pad
size relative to image size. The larger the pad , the less the image is likely
to distort. Often , the distance between the cliche and the body of the machine
will determine the maximum pad size you can use.
We
guide you to Use these following measures when choosing a pad shape for a particular
job: » | First,
at your end try your standard pads that you think would do the job for this particular
product. Then do a trial print to verify that the proposed print area is imaged
accurately. | » | The
round and the square pads are considered the most popular pads because these two
shapes can print the same object many a times and cover variety of products. | » | If
the pad shape you have chosen provides a satisfactory print over just a part of
the area, look for similar pad shapes that extent the profile in a way that will
cover the entire image. Distortion at the image edges is almost always caused
by undersized pads. | » | Whenever
possible, ensure that the lower point or apex of the pad does not come into contact
with the image area of the clinch. This tends to thin the link at that point,
causing an inconsistent ink deposit. | | » | If
the pad is "overstressed"(that is, too small for the image) or the image
is too close to the edge of the pad, distortion is likely to occur. Always use
as little pressure as possible to pick up and print the image. If the machine
is running too fast, excessive pad pressure can cause distortion as well as poor
ink transfer |
Hardness
of the pad :
The HARDNESS of
the pad is normally determined by the amount of silicon oil used when the pad
is made , Mainly four different hardness are standard in the industry and cover
most applications. As a general rule, the harder the pad, the better the performance.
However, a hard pad may be impractical in some applications, such as when using
a low-power machine or printing onto a delicate item. Choosing the proper pad
hardness for a job is a matter of experimentation and experience.
» | Hard
pads are most suitable for textured surfaces. | » | Use
softer pads when printing onto heavily contoured surfaces. Also use them when
printing onto fragile items. | » | You
must use a softer pad if you are using the electrical powered machines to achieve
a satisfactory action. | » | Avoid
using pads of different hardness on the same application, or the thickness of
the ink deposit will vary on the substrate. |
Top
Surface finish of pads :
You get Pads
with high gloss finish when you buy, you should remove excess silicon oil that
creates the glossy appearance ,to enable the pad to pick up and transfer proper
ink during the printing process. Typically, pad printers will use a strong solvent
for cleaning which damages the pad and shortens its life.
After you satin
finish the pad till its finish becomes nearly matte, the only other step that
must be taken prior to production is to gently wipe the pad with an alcohol-based
pad-cleaning fluid. This removes any free silicone oil . Once you have used the
pad, however, the best way to remove solid debris, dried ink , and dust is with
a quality brown packaging adhesive tape. By following this simple procedure, you
will improve your print quality, reduce downtime, and prolong the pad's life.
To
Retain Quality of PADS :
The better you treat them, the longer
they will last. Mechanical damage, aggressive solvents, and poor storage all take
their toll. But the real killer is a careless operator. If you make your staff
aware of how much pads cost, they may treat them with more care. Use a softer
pad if the power of your machine can't compress the pad sufficiently to achieve
a satisfactory rolling action. Although no hard and fast guidelines regarding
pad life are available, you can take a number of steps to get the most life from
all your pads: » | Use
a strong solvent only for first time initial removal of the silicone oil on the
super surface. | » | Use
a very mild solvent such as alcohol, or preferably an adhesive tape, if the pad
must be cleaned during production. | » | Always
use an brown packaging adhesive tape to remove debris and dried ink before starting
a production run. | » | Never
use too much of pad pressure during printing process. | » | Ensure
that the substrate is free of dust, particularly the sharp particles , before
you start printing. | » | When
possible, avoid printing near sharp-substrate edges. For that never print on to
an empty nesting fixture. | » | With
wood-backed pads don't let the screws penetrate into silicon rubber. | » | Use
as large a pad as is reasonable for the job. | » | Never
store a pad on top of other pad . | » | If
pads are supplied in a protective shell, use it when storing the pads in your
shop. | » | If
you continuously use strong solvents on printing pads they will cause them to
prematurely wear out. | » | Please
Handle and store the pads very carefully. |
One
other point about pad life is that many inks have aggressive solvents that will
be absorbed by the pad during printing. This absorption of solvents will cause
the image to "grow" on the super surface of pad, to the point that it
will eventually affect the print quality. At this point, you must stop the machine
and replace the pad with another pad of same shape and size. This isn't a permanent
condition, though: If you allow the original pad to stand for some time , the
solvents that have penetrated into it will evaporate, returning the pad to its
normal surface finish. You can accelerate this process by warming the pad. Then
you can use this pad again after some time.
CONCLUSION
on PADS :
Although the importance of pads is sometimes overlooked
in the field, remember that the process derives its name from these silicone-rubber
image carriers from plate to the substrate. Correct selection and care of pads
is essential. As with any process, pad printing has its limitations and it's best
to understand those before you choose a pad. Common sense and experimentation
will guide you. Overall, keep pad in good condition, and it serve you well.. |
