 Flexography
is a versatile process that can print on a variety of materials of varying
sizes. Flexography prints
items that we are in contact with daily including
cereal boxes, bottle labels, potato chip bags, frozen food bags, corrugated
boxes, newspapers and grocery bags.
The flexographic printing process is similar to a rubber stamp and ink
pad, but more sophisticated and on a larger scale. Flexography uses a soft, flexible
printing plate
with
a three-dimensional (3D) raised mirror image of the design. Plates are mounted on a
cylinder located on a
press equipped with anywhere from one to twelve color stations. Ink is placed on
the anilox roll,
transferred to the plate and from the plate to the
substrate.
While there are significant variations in flexography, this module attempts to
simplify the overall operation into three broad categories: prepress, press, and
postpress. First, the prepress
section includes everything needed to develop an image, from the idea stage to a
plate that can be used on a printing press. The press section includes both web-
and sheet-fed processes and incorporates tasks from loading raw substrate into
the press, to loading plates, filling inks and removing the finished product
from the press. Finally, the postpress section includes activities used
to further process the printed material into a finished item.
The following identifies
potential hazards and possible solutions to reduce the ergonomic hazards within
the flexography printing process:
Pre-press
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In the modern printing business most prepress work is
completed via computer. Images are delivered, checked and edited.
Potential Hazards
The hazards associated with this type of activity are
similar to those found in an office environment. Employees in the prepress area
may spend extensive amounts of time at the computer workstation developing
content. Workstations that are not properly designed for computer work may cause
stressful postures or motions.
- Prolonged periods of awkward body postures (i.e., neck bending, torso
twisting, raised shoulders, extended arm) (Figure 1).
- Repetitive motions (i.e., frequent reaching to a mouse, clicking and dragging)
(Figure 1).
- Contact stress to the legs and/or arms (Figure 1).
- Glare and poor lighting situations (Figure 2) increase muscle stress, such
as eye strain, and encourage awkward postures such as leaning forward to view
monitor.
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Figure 1. Poor workstation setup.
This person must reach up and away from his desk to operate the mouse and must
look to the side to view monitor.
Figure 2. Poor workstation setup due
to
glare from the window. |
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Possible Solutions
- Establish a training program so that employees can learn how to set up and periodically adjust their
workstations (Figure 3).
- Ensure keyboard and mouse are at proper height and position.
- Provide appropriate computer components and furniture.
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Figure 3. Proper workstation setup and posture.
(Roll mouse over text in the image above to
highlight specific areas.) |
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Flexographic platemaking involves
transferring images onto
photopolymer or rubber printing
plates. This transfer
may be from photographic negatives or digital computer-to-plate process. Plates
can be a variety of sizes depending on the size of the printing press and the
requirements of the job. During the platemaking process, plates must be
transported between the processor, drying drawers, plate cylinders and
storage drawers.
Potential Hazards
-
Frequent or prolonged use of forceful pinch grips to:
- Cut or trim film and masking materials using small- handled knives or film
cutters (Figure 4).
- Position or move film while on the platemaker (a 52" x 80" plate can
weigh in excess of 35 pounds).
- Lift and carry the plate between workstations (Figure 5).
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Frequent or prolonged torso bending to:
- Reach over large platemaker tables or processors (Figure 6).
- Place plates into or retrieve plates from processors trays or storage
drawers (Figure 7).
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Figure 4. Narrow, slick metallic handle
requires forceful pinch grips.
Figure 5. Transporting
flexographic printing plate using a pinch grip.
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Figure 6. Forward bending and reaching
over a “clam shell”-type plate
processor can increase strain
on a variety of muscles. |
Figure 7. Awkward bending to place plates into drawers of processing unit to dry. |
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Possible Solutions
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Press
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Flexo presses utilize rollers, sleeves, and cylinders to complete the
printing process. Operators have to tend to, remove, transport, or store
many of these press components. These tasks may require lifting of heavy
weight, often in awkward postures, especially on older machines where there
is little attention given to accessibility.
Anilox rolls
(Figure 14) are engraved ink-metering rollers used on flexographic printing
presses. They are typically ceramic coated
steel rolls of considerable size and weight. A doctor
blade spreads ink which has been applied to the Anilox roll, to create
a controlled film across the surface of the roll. Ink is then transferred
which .prints the image onto the substrate.
Anilox sleeves are used as an
alternative to anilox rolls. Also ceramic coated, they are hollow and
slide over steel cylinders which remain on the press.
Printing plates are mounted on
plate cylinders. For
narrow web applications lighter plates may be mounted on plate cylinders
either on or off the press. On wide web applications where the plate may
weigh several hundred pounds, mounting is generally done off the machine where
access is improved. Plate cylinders are seldom removed from corrugated
presses except for maintenance. The plates for this application are mounted on mylar and
attached in the press.
Plate sleeves
(Figure 15) are hollow
cylindrical plates that are fitted over
a plate cylinder. This makes cylinders lighter and easier to manipulate in wide
web and uninterrupted printing processes. |
Figure 14. A typical anilox roll.
Figure 15. Changing a lightweight plate sleeve is easier than positioning a heavy
plate cylinder on press. |
Potential Hazards
- Use of extended reaches (which may be above shoulder or head level) to
place or remove heavy cylinders/rolls from or onto storage racks.
Additionally, these reaches may be required when placing cylinders/rolls
into the press (Figures 16 and 17).
- Repetitive and forceful lifting
utilizing awkward postures such as torso bending and twisting to manually place or
remove cylinders/rolls from rack or press (Figure 18).
- Strain of the hand and fingers may occur when gripping and lifting cylinders when
the cylinders size is too
large for good hand coupling.
- Rolls, sleeves or plates may be too heavy for individuals to
manually lift.
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Figure 16. Restricted access or storage position
may require reaching away from the body or above shoulder height to place a roll
on the rack.
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Figure 17. The operator is attempting to
lift a 45 pound anilox roll above his head.
Notice
the box he has to stand on to reach it. |
Figure 18.
Restricted when working at the press may force employee
to bend and reach during anilox removal
and installation. |
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Possible Solutions
- Consider the design
and placement of storage systems and cleaning equipment. Storage systems
should be close at hand, easy to access, and at a comfortable working height.
The floor area surrounding the storage systems should be kept clear of debris,
finished labels, roll stock, ink buckets, etc. to prevent tripping and improve
access.
- Use storage racks that are at the ergonomically correct height (usually
between knee and shoulder height), easily
accessible and minimize bending and reaching (Figure 19). Do not store rolls under work benches.
- Keep work objects or materials close to the body when lifting or carrying (Figures 20 and 21).
- Reduce the weight of items to be lifted by:
- Whenever possible, solid steel rolls should be phased out in favor of
lighter weight, thin-walled hollow steel anilox rolls. They can reduce
the weight of anilox rolls by as much as 2/3. A 19" solid steel anilox
roll weighing 90 pounds can be replaced with a thin-walled, hollow steel
roll weighing only 35 pounds.
- Other ways to lighten rolls include manufacturing from aluminum,
aluminum tube with steel
journals, or carbon fiber with steel journals.
These products will significantly reduce the rolls’ weight, but
may increase the cost and may require additional care when cleaning
or resurfacing.
- Ensure that engineering and administrative controls are implemented for
handling rolls that are heavier than about 50
pounds or which can not be handled in close to the body at about waist height,
including:
- Overhead gantry or pivot cranes to
lift rolls from machines or racks.
- Fork lifts or pallet trucks to
lift, lower, and transport rolls or racks.
- Multiple employees working together
to perform lifts of heavy objects.
- Reduce anilox roll changes by
standardizing process specifications. For example, running jobs which can use anilox rolls
with the same specifications will require fewer roll changes.
- Use carts or integrated systems to minimize manual handling of sleeves or
rolls.
- Provide a roll stand that mechanically lifts and positions rolls (Figure 22).
- Provide a cart or floor tram (Figure 23) to move large
cylinders. Once manually moved in front of the printing press, the cylinder cart
is coupled to a motorized positioning device that automatically moves the cart
to the locations that are required for deinstalling
and installing the hardware.
- Provide a programmable floor tram controlled by laser and inductive
cable. This may be used to transport sleeves
and cylinders between different work areas such as mounter proofer,
storage area and transfer station (Figure 24).
- Replace heavy plate cylinders with lighter weight (5-10 pounds) air sleeve
cylinders (Figure 25). This minimizes heavy lifting and awkward postures by
letting machinery and forced air do the work.
- Process includes the following steps: applying air to the plate cylinder;
slide off current sleeve (with plates still mounted); slide on new sleeve
with the plates for the next job; and remove air source to affix the sleeve in place.
[1.3 MB Demonstration Video,
Windows Media Application | Text Version.]
Video Text Version: Flexible printing plates are
mounted onto heavy print cylinders which are then lifted onto the press. An
alternative method is to use a lightweight, rigid sleeve which quickly and
easily slides over the print cylinder already on the press. The sleeve can be
used with normal plates, or covered with rubber or photopolymer, engraved or
exposed, to create the required image. This has the additional advantage of
being seamless, so it is especially useful for continuous designs, such as wallpaper.
Accessibility Assistance: Contact the Directorate of
Cooperative and State Programs, Outreach Services and Alliances at
202-693-2340 for assistance accessing OSHA Windows Media materials.
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Figure 19. Storage of anilox rolls on racks placed
no higher than chest height will minimize
reaching.
Figure 20. Proper lifting of a roll.
Figure 21. Carry cylinders close to the
body and at waist level.
Figure 22. Cylinder cart, used for changing sleeves,
or anilox rolls.
Figure 23.
Manual floor tram for transportation of the cylinder cart.
Figure 24.
Programmable floor tram to transport sleeves and cylinders.
Figure 25. Mounting a flexographic printing plate
on a lightweight, rigid sleeve instead of a heavy,
plate cylinder.
See a short demonstration
video
[1.3 MB
Windows Media Application
| Text Version.] |
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Press ink must be stored, transported, mixed, and loaded
into presses before the printing process can begin. Ink is purchased in large volumes
ranging from 5 gallons to 1000 liters (about 300 gallons). Smaller volumes may be poured and mixed manually.
Larger volumes that weighing in excess of 10 pounds must be dispensed using pumps and manually put in place. After
the ink is mixed it is placed into containers
(usually kits) which are transported to the press on carts or pallets. Once at
the press, ink may be pumped from the kit to the ink fountain. Smaller volumes
may be manually poured.
Potential Hazards
- Forward bending to reach low
locations or reaching overhead to retrieve ink containers
from pallets, shelving or stacks (Figure 26).
- Force needed to lift or move (may include use of hand truck) heavy ink containers and drums
(50 to 600 pounds).
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Force needed to lift and set heavy pumps
and lids (more than 10 pounds).
- Awkward bending of the wrist when pouring ink into ink fountains or
containers (Figure 27).
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Figure 26. Press return ink is stored in 5 gallon
pails. The hazard of lifting heavy pails is increased by high or low lifting
heights and poor access.
Figure 27. Awkward bending of the wrist when pouring
ink into ink fountains on press. |
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Possible Solutions
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Web presses print on rolls of
substrate including paper,
film and foil. The finished product is generally collected on another large rolls
at the end of the press. Rolls must be loaded onto and removed from
the press.
Potential Hazards
- Forceful and repetitive gripping is used to grasp and move rolls between the
supply pallets and press feed areas.
- Forceful and repetitive gripping is used to grasp and remove finished
rolls for further processing.
- Heavy lifting and physical strain while manually moving rolls between the
press or pallets (Figure 31).
- Forward bending to lift substrate rolls from
lower areas of supply pallets (Figure 32).
- Forward bending to stack rolls of finished product on pallets.
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Figure 31. Lifting rolls from press.
Figure 32. Heavy lifting of rolls from
supply pallets. |
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Possible Solutions
- Keep elbows close to your body when manipulating heavy rolls to reduce physical
strain.
- Use a lift or other mechanical assistance to remove rolls from turrets,
conveyor belts and pallets (Figures 33
and 34).
- Use a lift to maneuver rolls of stock and finished product (Figure 35).
- Using lifts may benefit overall efficiency and quality by increasing the number
of finished rolls a packer can safely handle. This may also eliminate unnecessary carrying
and manual transferring reducing the potential for damage to finished rolls.
- Design a track system where rolls can be positioned on a
turntable platform and pushed along the track into position.
- Provide education and training on use of safe body mechanics
when pushing, pulling and lifting materials.
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Figure 33. Remove rolls of material with a
mechanical lift.
Figure 34. Material handling equipment safely lifts heavy rolls of substrate.
Figure 35.
Use a lift to
place finished rolls onto and remove supply rolls from a pallet. |
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Some presses print
on individual pieces of flat stock such as corrugated board. Pressmen working with
stacks of flat stock are exposed to a
number of potential ergonomic hazards when loading or unloading a press.
Sheets can be large, heavy and awkward to handle.
Potential Hazards
- Forceful and repetitive gripping using elongated grip may be required to:
- retrieve stock from supply pallets and transport to press loading
area, and
- to move finished product stacks for further processing.
- Use of extended reaches (which may be above shoulder or head level) to retrieve or place stock from tall
piles.
- Torso bending to place or retrieve stock from low locations such as
pallets on the floor or tables (Figure 36).
- Extended reaching and torso bending to feed stock into press.
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Figure 36. Reaching and bending are necessary to
handle large loads or when work tables are too low. |
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Possible Solutions
- Provide employees with tools to minimize reaching and bending, including
push bars for pushing and manipulating materials.
- Minimize elevated reaches (which may be above shoulder or head level) to stock, controls or feed area by using platforms to raise
employees to proper height (Figure 37).
- Generally a stack should be limited to no more than about 1-1/2 to 2-1/2
inches. This is easier on the back and minimizes the finger force that must be
exerted. Encourage employees to lift and carry less material more frequently
rather than heavier loads less often.
- Consider using visual markers such as lines drawn on a stack of materials
to suggest to employees the amount of material to be handled at one
time.
- Use height adjustable carts (Figure 38) to transport stock to
and from the printer. Adjust the height of
the cart to be the same height as the press feed and discharge so that stock
can slide on and off without the employee having to reach and lift.
- Provide
palletizers or scissors lift at the press so that stock can be unloaded and loaded at a proper
height. These devices keep the height of a load at about waist height by
raising the height as supply is removed from the pallet.
- Do not stack items in tall stacks that require elevated reaches.
- Use a waist mounted belt to support the bottom
edge of the substrate sheets (corrugated material). This should minimize
bending and twisting keeping the load at waist height and directly in front
of the body. Forceful pinch grips are minimized because weight is supported
by the belt.
- Pull the sheets from the table or stack to the
beltline, support the bottom edge against the belt, then lift the sheet up
using the belt as a pivot point and transport to the new location.
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Figure 37. Standing on a platform allows employee
to keep elbows in close to the body when stacking material.
Figure 38. Height-adjustable cart minimizes bending and reaching for stock. |
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Post Press
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Depending on customer specifications, printed products may be packed,
banded or sheaved, or palletized before it is shipped.
Bundled product can be heavy and loading may be from near ground level to above head height.
The product may be slick and require excess finger force to keep product in stacks. After a load has been prepared on a pallet, it is generally wrapped with
plastic to maintain its integrity during transit.
Potential Hazards
- Torso bending, twisting and reaching out and away from the body to:
- Grab bundles on the conveyor before they
arrive.
- Place items on pallets. The height of material on the
bottom of the pallet is typically only a few inches above the floor (Figure
39).
- Manually wrap plastic around bottom of the pallets while supporting
the plastic wrap dispenser (Figure 40).
- Forceful, repetitive gripping to:
- Retrieve printed materials from press.
- Load materials onto pallets or into boxes.
- To hold rolls of plastic wrap while wrapping around pallets.
- Bundles transported between press and pallet may be too heavy or too bulky to lift.
- Physical stress associated with positioning large plastic wrap rolls into
automatic wrapping machines.
- Repeated lifting of wooden pallets weighing between 40 and 70 pounds may
cause stress to the lower back, arms, elbows and shoulders.
- Prolonged periods of standing to:
- Feed presses.
- Collect and palletize finished product.
- Wrap and pack product.
- Awkward hand and arm postures to place materials in packing box.
- Repetitive hand and arm motions are required when sealing packages using
handheld tape gun.
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Figure 39. Loading and unloading lower level of
palletized product requires deep bending and extended reaches.
Figure 40. Manually wrapping a pallet can require
torso bending. |
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Possible Solutions
- Eliminate or minimize
manual material handling by:
- Using mechanical means,
including hoists,
lift tables, and stackers.
- Using carts to transport product from one location to another. Push
instead of pull whenever possible.
- Use conveyors to move materials directly to the next step or process without palletizing (Figure
41).
- Conveyor should be coordinated with press (at equal height) to
allow material transfer with minimal lifting.
- Materials should be slightly below waist height and close to the
employees body at the unloading end of the conveyor (Figure 42). This will allow
the employee to lift and stage loads without bending or
reaching.
- If conveyors are too high, use of a platform will allow shorter
employees to work at proper height.
- Elevate the pallets used for receiving processed
materials to minimize bending by:
- Using height-adjustable lift devices to keep the load close to waist level.
Some height-adjustable devices also rotate. This enables the employee to position
the load close to the body by turning the pallet
(Figure 43).
- Using a forklift to position pallets off the floor and
at a matching height adjacent to the conveyor.
- Placing pallets on a platform that positions the load close to waist
level.
- Placing the pallet on several other empty pallets to raise the height. Secure the
lower pallets to increase the stability of the stack (Figure 44).
- Optimize load size and weight for one-person lifting. Generally, a
load should not weigh in excess of
40 pounds.
- Use a wedge, provide adjustable
packing stands, or build a table at an angle so
that the box opening is
tilted toward the loader
and improves access to box interior (Figure 45).
- Consider using boxes with one removable side.
- Minimize twisting of torso when loading between conveyor and pallet. Move
the feet to face the load instead of twisting. Place
box or pallet close to conveyor.
- Use automated taping, banding or wrapping machine (Figure 46).
- Use rolls that weigh as little as
possible to minimize the lifting hazard if manual plastic wrapping must be
performed.
- Consider the use of an automatic pallet wrapper and an automatic strapping machine
to reduce repetitive motions and awkward postures (Figure 47).
- Use lighter, plastic pallets. Plastic pallets can weigh half of what a
wood pallet weighs. The employees of both the company
and the customer will benefit from the reduction in weight being lifted
(Figure 48).
- Provide anti-fatigue mats and/or sit/stand stools (Figure 49).
- Change the handling method to lowering instead of lifting, if possible.
Ensure proper lifting techniques are used even when lowering.
- Consider job modification or rotation to reduce the exposure time for these
tasks.
- Train on proper lifting techniques.
- Keep back straight.
- Keep elbows in close to the body.
- Lift with your legs.
- Get firm grip.
- Do not twist back.
- Move load smoothly
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Figure 41. Use a conveyor system to move product to
the palletizing position.
Figure 42. Feed and take off tables can be adjusted to a coordinated height that
minimizes awkward postures and lifting.
Figure 43. Pallet lift that automatically
adjusts to the correct height
based on pallet weight.
Figure 44. When manually wrapping
pallets, elevate them
to
avoid awkward positions.
Figure 45. Use a packing stand to reduce wrist
and torso and bending.
Figure 46. This machine automatically applies tape to the box, which reduces
employee overexertion.
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Figure 47. A semi-automatic pallet wrapper which can run independently of an
operator once it has been setup. |
Figure 48. Plastic pallets weigh between 20 and 30 pounds. |
Figure 49. Anti-fatigue mat can be
placed around machines
to reduce the stress of standing
for long periods of time.
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