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Theory of Operation
The Drying system uses an Allen Bradley PLC with Operator Interface
Touch screen controlled combination of heated air knife streams,
radiated heat from short wave (SW) or medium wave (MW) dryer
panels, and air evacuation in order to produce quality results. The
Drying System consists of the following major components:
· Drying System Cabinet
· Air Knife, Motor and Blower
· Air Evacuator Motor and Blower
· Operator Interface Touch screen
· Drying Cassettes to include:
The following describes the typical operating procedure for drying:
1. The aqueous coated sheet will pass under the first Short Wave IR
Dryer (SWIR). The short wave energy heats the substrate to evaporate
solvents from the ink (NOTE: All coatings are porous), which
accelerates the drying process. Short wave energy does have a minimal
drying effect on aqueous coating due to its chemical composition. The
aqueous coated sheet then passes under the first Medium Wave Dryer
(MWIR). The medium wave energy heats the surface of the substrate
further accelerating the evaporation of solvent from the ink. Medium
wave energy has a positive effect on aqueous coating due to its
characteristics of being “color-blind”.
2. After the sheet passes the first SWIR and MWIR Dryer, it is
“scrubbed” by two dual heated air knives that are crucial in setting up
aqueous coating. The coated sheet must be scrubbed of excess water,
which is the main component of aqueous coating. The volume of air
will determine the effectiveness of the scrubbing action, and heated air
accepts moisture more readily than ambient or chilled air.
3. Once the sheet is scrubbed of excess moisture, an evacuator hood
is placed adjacent to the heated air knife section to remove the
moisture-laden air fro the press extension and / or delivery area.
4. The processes in steps 1, 2 and 3 are repeated again for
additional dwell time up to two more times. Through extensive testing
we have found that more dwell time is allowed in the drying process,
the more effective it will be.
5. MWIR Dryers are used to compliment the effect of the SWIR
Dryers. SWIR Dryers are not colorblind; light colors and metallics
reflect heat and dark colors absorb. The effect on opaque or
transparent coatings is minimal, but the intensity of SWIR Dryers is
required for high speeds, heavy stocks and / or board.
6. MWIR Dryers are colorblind. They affect the ink, coating and
varnish the same. However, they do not have much intensity, which is
needed for high speed, heavy stock and / or board. The combination of
SWIR and MWIR as with this drying system, is a perfect balance to
cover all situations.
7. Some presses may be equipped with a delivery hood to remove
excess heat and spray powder from the press extension. All delivery
hoods should be equipped with a damper. Upon start-up, the damper
should be adjusted to remove the “right amount” of excess heat and
spray powder. An un dampened delivery hood will create spray unit
application problems.
8. Drying Package evacuators and / or delivery hoods are not
designed to remove excessive coating odor. If excessive coating odor is
present with the drying package and delivery hood, consult your
coating manufacturer. Chemical substitutions can be made to alter
coating odor without sacrificing performance.
9. If the Drying Package is supplied with a delivery pan cooling
option, this option is used to prevent heat warpage of the lower press
pans or guiding mechanism. The pan cooling option is not used to
remove heat fro the printed or coated sheet.
10. With the printing / coating process, it is crucial to maintain
correct pile temperature. Too much or too little heat can cause
spoilage. In our experience, optimal pile temperatures for process
work and coating jobs are as follows:
a. First Pass 96º - 98º F (35.5º C - 37º C)
b. Second Pass 92º - 95º F (33º C - 35º C)
11. Always consult your coating supplier for their
recommendation. The pile temperature readings should be taken at the
darkest color printed and approximately 2” (51mm) down into the
pile. This drying system includes a hand held optical pyrometer for
accurate pile temperature sensing.
12. All aqueous coatings are not created equal. Typically, work
and turn coatings will have a faster dry rate than high gloss coatings.
Your coating manufacturer can tailor individual coatings to your
specific needs. Always choose an established, reputable coating
manufacturer. These manufacturers have been in the coating business
for a great deal of time, and the knowledge they have will be invaluable
to the success of your operation.
The Drying system uses an Allen Bradley PLC with Operator Interface
Touch screen controlled combination of heated air knife streams,
radiated heat from short wave (SW) or medium wave (MW) dryer
panels, and air evacuation in order to produce quality results. The
Drying System consists of the following major components:
· Drying System Cabinet
· Air Knife, Motor and Blower
· Air Evacuator Motor and Blower
· Operator Interface Touch screen
· Drying Cassettes to include:
- Heated Air Knife shells and Air Evacuators
- Short Wave IR Panels
- Medium Wave IR Panels ( high intensity)
The following describes the typical operating procedure for drying:
1. The aqueous coated sheet will pass under the first Short Wave IR
Dryer (SWIR). The short wave energy heats the substrate to evaporate
solvents from the ink (NOTE: All coatings are porous), which
accelerates the drying process. Short wave energy does have a minimal
drying effect on aqueous coating due to its chemical composition. The
aqueous coated sheet then passes under the first Medium Wave Dryer
(MWIR). The medium wave energy heats the surface of the substrate
further accelerating the evaporation of solvent from the ink. Medium
wave energy has a positive effect on aqueous coating due to its
characteristics of being “color-blind”.
2. After the sheet passes the first SWIR and MWIR Dryer, it is
“scrubbed” by two dual heated air knives that are crucial in setting up
aqueous coating. The coated sheet must be scrubbed of excess water,
which is the main component of aqueous coating. The volume of air
will determine the effectiveness of the scrubbing action, and heated air
accepts moisture more readily than ambient or chilled air.
3. Once the sheet is scrubbed of excess moisture, an evacuator hood
is placed adjacent to the heated air knife section to remove the
moisture-laden air fro the press extension and / or delivery area.
4. The processes in steps 1, 2 and 3 are repeated again for
additional dwell time up to two more times. Through extensive testing
we have found that more dwell time is allowed in the drying process,
the more effective it will be.
5. MWIR Dryers are used to compliment the effect of the SWIR
Dryers. SWIR Dryers are not colorblind; light colors and metallics
reflect heat and dark colors absorb. The effect on opaque or
transparent coatings is minimal, but the intensity of SWIR Dryers is
required for high speeds, heavy stocks and / or board.
6. MWIR Dryers are colorblind. They affect the ink, coating and
varnish the same. However, they do not have much intensity, which is
needed for high speed, heavy stock and / or board. The combination of
SWIR and MWIR as with this drying system, is a perfect balance to
cover all situations.
7. Some presses may be equipped with a delivery hood to remove
excess heat and spray powder from the press extension. All delivery
hoods should be equipped with a damper. Upon start-up, the damper
should be adjusted to remove the “right amount” of excess heat and
spray powder. An un dampened delivery hood will create spray unit
application problems.
8. Drying Package evacuators and / or delivery hoods are not
designed to remove excessive coating odor. If excessive coating odor is
present with the drying package and delivery hood, consult your
coating manufacturer. Chemical substitutions can be made to alter
coating odor without sacrificing performance.
9. If the Drying Package is supplied with a delivery pan cooling
option, this option is used to prevent heat warpage of the lower press
pans or guiding mechanism. The pan cooling option is not used to
remove heat fro the printed or coated sheet.
10. With the printing / coating process, it is crucial to maintain
correct pile temperature. Too much or too little heat can cause
spoilage. In our experience, optimal pile temperatures for process
work and coating jobs are as follows:
a. First Pass 96º - 98º F (35.5º C - 37º C)
b. Second Pass 92º - 95º F (33º C - 35º C)
11. Always consult your coating supplier for their
recommendation. The pile temperature readings should be taken at the
darkest color printed and approximately 2” (51mm) down into the
pile. This drying system includes a hand held optical pyrometer for
accurate pile temperature sensing.
12. All aqueous coatings are not created equal. Typically, work
and turn coatings will have a faster dry rate than high gloss coatings.
Your coating manufacturer can tailor individual coatings to your
specific needs. Always choose an established, reputable coating
manufacturer. These manufacturers have been in the coating business
for a great deal of time, and the knowledge they have will be invaluable
to the success of your operation.