When
the ink can not be absorbed or penetrate the surface you wish to print,
you can not lay your screen directly onto the surface to be printed
or the design will blur/ smudge when printed.
The screen must be raised
above the item to be printed by approx. 3-5mm, to create an
'off contact' style of printing. After your squeegee passes
over the design area, and the ink is printed onto your item,
the screen 'snaps' back upwards and the ink is left sitting
on top of the item.
Important note on screen size
As the screen is elevated
and must travel down to the item, there is a limitation on the
size of your design in relation to the overall size of the screen
- you can not print to the edges of the screen as with fabric
printing.
With the extreme edges of
the screen unusable the general rule is to have your design
one third the size of your screen.
This rule however is a guide only, as sizes printed are normally
bigger than that suggested below:
S-9100 Small Plastic Frame
- Design size 40 x 60mm
S-9101 Large Plastic Frame
- Design size 60 x 80mm
S-9102 Small Metal Frame
- Design size 100 x 160mm
S-9103 Large Metal Frame
- Design size 150 x 300mm
S-9104 XL Metal Frame
- Design size 375 x 450mm
Example: You can print a full CD-ROM using
an A3 Metal Frame [S-9103]
You
must use a screen printing jig to print your design
Printing 'off contact' is an advanced application, however
with the right equipment the task is made very simple and actually
no harder than fabric printing.
The best thing you can do is forget printing by sight/ hand
registration and invest in a screen printing jig:
Essential for correct height
adjustment
Provides registration
Correct height
The aim is to elevate the screen above the item to a point just
before the edges of the design can not be pressed down onto the item
without stretching the screen.
1. Place
a copy of your original artwork onto the jig and
create two alignment guides for the item.
This can be
done by placing two pieces of plastic [two edges
off the pieces of the Height Adjusters] along two
sides of the item and tape firmly to the base of
the jig.
2. Insert
height adjusters [Plastic Height Adjusters are available
from NEHOC code S-9112] into the hinge of the jig.
The screen
now needs to be raised above the item to be printed
as high as possible without the edges not coming
into contact when printed. The normal height is
approx. 3-5mm however this may increase for solid
areas which will 'stick' in the middle when printed.
3.
Press down gently
on the top of the screen on your screen to check
the height.
If all the
screen comes in contact then remove the frame and
increase the height again.
4. If required,
increase the height slightly by adding another layer
of Plastic Height Adjusters
When the edges
are too high and can not come in contact with the
item below, the screen is too high and must be lowered
slightly. This is the maximum height available.
5. Test the height again
and make adjustment if required.
Note in some
instances you may require as many as 8-10 adjusters
under your screen - such as when printing a CD-ROM
[design located in the middle of the frame] with
an A3 Metal Frame. The actual height is not important,
it's about checking the design to make it as high
as possible without lifting the edges too far.
Hint:
After you have printed off contact a few times, judging the height is
very fast, however if you are a beginner don't stress out, just try
a few 'dry' prints with your squeegee first to check the height. You
are looking for a clean contact with the edges of the design without
having to press too hard.
When the
screen is too low
You will know very quickly
as your prints will be:
1. Blurred or smudged:
As the ink is printed the screen has not lifted and moves [the
most minor vibration will cause a blur]
2. Printed item sticking
to the back of the screen: Firstly check the base of the jig
has not lost its adhesive - if so put on more Table Adhesive
and try another print. If the screen is too low the ink does
not print and stays in the screen to which the item will stick.
Adjusting
after you have started to print
If you perform your first
print and find the item blurred or sticking [because the screen
is too low], then you have two options:
1. Recommended option - Remove your screen completely
and wash down under cold water to remove all the ink and clean
the screen [so you don't have any printing problems]. Return
the dried screen back to the jig and increase the height.
By washing out you will have a much better view through
your screen of the item below for registration and this also
stops any problems with the screen drying.
2. Quickly loosen the jig hinges and insert another
layer of Plastic Height Adjusters under the frame [or more if
required]. Insert the frame and align over the item, however
this is now more difficult as the ink will leave a mark on the
screen making vision of the item underneath harder. Once registered
commence printing again.
If you are too slow then the ink may dry in the screen
and you will have to wash out anyway.
Re-Registration using this process is more difficult