PAGE
11
. 21
Screens
Image registration is composed of two elements: accuracy and
repeatability. Accuracy is the extent to which the original has
been duplicated in size. This is not usually a concern for the
garment printer. For example if the image is to be 18-inches
long, we dont often care if it turns out to be 18 1/8-inches
long but we do care that all of the colors that build the image
line up. That is if they all turn out to be precisely 18 1/8-inch-
es long. If you are running close tolerance work, process color
or cut-piece stock to be sewn after printing, the off-contact
setting is crucial (refer to page 4.4 for complete details on off-
contact distances).
IImm
aaggee TToolleerraannccee
The table (figure 1.18, page 1.23) and graph (figure 1.19, page
1.24) present a nominal off-contact distance of 1/8 (0.125)
and various sized inkwells to demonstrate what happens to the
tolerance of the image as the size of the ink well diminishes.
For a working reference we have listed the Lpi or ruling of the
halftone that can be run at these settings. Bear in mind that
Smaller length or width frames
will force the screen holders to sit
on the platen or hang suspended
at an angle and result in extreme
print problems such as blurring,
smearing and premature mesh
fatigue. Using smaller frames than
the recommended size, (squeegee
and off-contact distance being
constant) will cause the following
problems:
1. Force the frame holders to sit
on the platens.
2. Reduce the range of acceptable
off-contact settings.
3. Force you to print a smaller
image.
4. Will cause the mesh and stencil
to fatigue and breakdown
faster.
5. Make registration very difficult.
Consequences Of
Consequences Of
Using Smaller
Using Smaller
F
F
rames
rames
Essentials of Press Set-Up
Squeegee Holder
Squeegee Blade
Side Ink Well
Screen Frame
Platen Surface
Rear Ink Well
Front Ink
Well
Off Contact
Distance
Figure 1.15 This drawing illustrates the platen, screen frame and squeegee
and the main components of the following section. You may want to review
Chapter 5 for detailed discussions of these components from an on-press per-
spective.