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Where
Does This Image Go?
Print positioning made simple
by Douglas Grigar, Master
Screen Printer
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(A version of this article originally appeared
in the January 2005 issue of PRINTWEAR.)
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You may already have a plant standard for
the placement of prints on “normal”-sized T-shirts - where
a full-front, full-back, or left-chest design will be printed - but
how is placement determined when an order for prints on the zipper pockets
of backpacks comes into the shop?
The confusion with print placement is much
deeper and more widespread than you might think. One of the most-asked
questions by new screen printers is about positioning of the printed
image on a regular T-shirt; but even with experienced printers, the
mention of positioning a print on an unusual item like the pocket of
a bag brings frustration.
If art positioning on screens in your plant
involves guesswork and every press set-up involves a T-square, there
is room for a set of standards to help improve consistency and efficiency.
The cost of a small, high-center back print mistakenly printed in the
“heart position” on a large order certainly negates the
statement, “We don’t have time to make a grid or build a
set-up table” (see Figure 1).
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[Figure 1: Oops! Print-placement mistakes
are a result of poor communication and a lack of standards. (All images
courtesy of the author.)]
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Think Backwards
The real trick for any plant is to work
backwards from the press. In other words, make all the steps prior to
the least flexible part of the process fit the needs of the
press. Yes, you read that right, the press is the least flexible part
of the positioning process. If an image is too small, too large, or
placed on the wrong portion of the screen, there is no way to reasonably
expect the press to print that art onto the product. Sure, we’ve
all heard or have our own stories about how we made some impossible
screen work by printing in ways worthy of Harry Houdini - or stretched
the limits of what duct tape was ever designed for - but we definitely
don’t want to make such gyrations standard procedure.
Do You Have What It Takes?
Once you have the product in hand - or
have its specifications and measurements - you can make determinations
about what press, platens, and screens you’ll need to make the
print.
Make sure the platen will hold the product
in a way that can produce a good print. A product must also be loaded
onto the press in a way that is reasonable and possible for production
to make a profit with the time invested. The best loading procedure
may be in a position not previously considered; for example, a long
but shallow gym bag may be loaded from the side of the platen rather
than from the top to bottom or bottom to top. Unusual items will often
need special platens or attachments, or even unconventional art-to-screen
placement. Careful planning and measuring are always needed.
Product Dictates Equipment
Forty years ago a T-shirt press was considered
an odd specialty printing press; now shops can expect at least a change
in platens for assembled textile goods. Printing in awkward spots or
when the product has protrusions (bag handles, pack straps, reinforcing
seams, or protruding snaps or buttons), special platens or positioning
may be needed. If the image is not far away enough from a protrusion,
that raised area may hold the mesh above the product causing distortion
or smearing when printing. The best answer for projecting parts of a
product is to have the projection fold over the edge of a platen or
build a recessed pocket or channel for the seems or buttons to fall
into (see Figure 2).
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[Figure 2: Special product placement
is often needed to prevent projections, such as straps, from interfering
with the print. This image is upside-down from what a T-shirt print
would be on the same platen.]
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Start With the Stopping
Points
Where and how the press holds the screens
is the starting point, and placing the press with a correctly
loaded screen into the printing position will allow measuring for positioning
to begin. Make an observation as to where the mechanical parts of the
press can be moved and where the movement is anchored. Using a rear-clamp,
multi-head, multi-platen manual press as an example, we can see that all
of the press operations radiate out from the center of the machine (see
Figure 3). Platens can move to or from the center of the machine on the
printing arms, and a rear clamp has some side-to-side movement available
to the screen frame. There will be a position with each screen size used
where the platen best matches the “sweet spot” on the screens;
that position should be the standard upon which all art placements should
be based.
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[Figure 3: Judging placement issues
starts by understanding how screens are locked into the press, how platens
move, and from where the movement of the machine is based.]
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Know the Sweet Spot
Screens have a “sweet
spot” and inside that area is where the screen will produce the
best print and hold the best registration. Generally, that sweet spot
will be within the center of the screen frame and consist of less than
65% of the available mesh. While 65% may sound like a small area, it is
necessary to avoid placing art into the “high distortion”
areas of the screen that can cause registration problems (see Figure 4).
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[Figure 4: Optimum art placement on
a screen takes into consideration the higher distortion areas and room
for squeegee and ink at the ends of the stroke.]
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The squeegee needs room for effective movement
and should have a little extra room at each end of the print stroke for
an “ink well.” Print strokes should start and end with enough
room to prevent the squeegee blade or handle from hitting the inside of
the screen frame.
Finding the Balancing Points
Using our manual-press example, we can see
that we would want to match our screen’s “sweet spot”
with an adjustable platen to find the perfect placement where the print
is positioned in order that, when the product is loaded, the print is
in the desired location. The clamp has little or no latitude in and out,
but some in the side-to-side direction. The platen has considerable movement
in the outward radiating direction (as seen in Figure 5). Most presses
are designed to have enough latitude for several screen sizes, and each
screen size will likely have different platen positions.
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[Figure 5: The screen clamp has little
or no latitude in and out, but some in the side-to-side direction; whereas
the platen has considerable movement in the outward radiating direction.]
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Coordination Starts With Art
The coordination of print placement
from art to screen to print works best when the three steps and their
mechanical requirements are literally charted out. Taking Figure 6 as
an example, the black lines represent the platen and the press clamp,
while the solid purple lines represent the screens to be used. The red
dotted lines represent a full-size print and the approximate placement
of a “heart print.” The graph shows the positioning of the
art area inside the screen’s “sweet spot,” and the platen
drawing has been positioned to hold a shirt (represented by the green
dotted line) so that the print area starts about three inches from the
collar. Graphs of this type can be made in any computer vector-illustration
program and can be modified to find positions for unusual platens and
products. The graphing also helps in placing art onto screens in the optimum
position, and the drawings can also be used to take measurements (as long
as they are actual size or to scale) and make screen set-up jigs and grid
tables.
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[Figure 6: The coordination of print
placement from art to screen to print works best when the three steps
and their mechanical requirements are literally charted, with a placement
grid such as this.]
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| Setting and Using Standards
Another benefit to placement coordination
is the elimination of location mistakes. Once a graph is drawn, art grids
can be produced that let placement be determined by art production. Standardized
grids and registration markings help control and communicate placement
instructions without excessive notations that can be missed, lost, or
misinterpreted. For example, if an order for team shirts is taken and
the customer requests that there be a space at the top of the back print
for heat-transfer player names, a standard set-up can be used to place
the art lower than normal for special placement, and measuring concerns
may be addressed in art preparation.
Figure 7 shows how the registration marks
(circled in red) can be used to help position the art onto the shirt to
allow sufficient space to transfer individual names. The registration
marks not only aid in aligning the colors from screen-to-screen, but can
be used to position the screen relative to the platen.
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[Figure 7: The registration marks (circled
in red) help position art onto the shirt; they not only aid in aligning
the colors from screen-to-screen, but in positioning the screen relative
to the platen.]
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| While most programs that can create
color separations will provide set registration marks, the marks are often
equally spaced and are often at the corners of the printed positive; maximum
usefulness is gained by a dual-centered mark approach, with a single offset
mark. The centered marks help in platen alignment, and the third mark helps
in leveling and color registration. An offset register mark also provides
the added feature of denoting a clear direction of the positive. In Figure
8 you will note that the offset registration mark and the standard placement
of the order information makes shooting the film incorrectly onto a screen
less likely. Also, there will be less confusion and guesswork if the colors
and order information are exposed onto the screen along with the image and
registration marks. |
[Figure 8: Note that the offset registration
mark and the standard placement of the order information makes shooting
the film incorrectly onto a screen less likely.]
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| On the Printwear website
(www.printwearmag.com/placement) three Illustrator files are available for
download: a generic grid and platen drawing for use as a starting point
for this process, along with two vector-program “starting files”
with registration marks that match the generic grid. The files are provided
free as an industry service and are available in editable form for each
plant that wishes to use them as a basis for establishing a standard placement
procedure. |
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