IMPORTANCE & MAINTENANCE OF RUBBER ROLLERS
printing machine is desired to deliver optimum
performance. In any machine the printing
section is considered the important section, the
process of ink considered the important section, the
process of ink transfer to the surface becomes the
vital point for quality outputs. Thus in a way
the "Rubber rollers" which actually
transfer the ink can be treated as the heart of the
print quality can be heavily hampered if proper
attention is not paid towards the rollers, as it is
directly associated in ink transfer. But
that's not all the rubber rollers not maintained
properly leads to other indirect losses, some of
them are :-
- Frequent replacement of
- Plate wear due to
incorrect quality of rollers.
- Wastage of proper
printed matter due to uneven inking.
- Scumming due to
number can go on increasing, but the message if this
exercise is to emphasize the importance of the
Rubber Rollers. Without proper care they can
eat up a substantial amount of the profit and many
time it is not even recognized!!!
most expensive thing in printing is
"DOWNTIME" of the machine. It can
cost a substantial amount of money per day and one
of the common reasons for it is Defective Rollers or
Rollers requiring change.
Thus it is very
necessary for printers who strive for quality should
understand the methodology of proper use and care of
the Rubber Rollers.
PROBLEMS CAUSED BY FAULTY ROLLERS
Scumming is the
appearance of unwanted inked are in the
non-image area. One of the important
reasons for scumming is inadequate supply of
water to the plate. Dampening rollers
should be soft & should be capable of
supplying very thin even layer of moisture to
the plate. Hard or uneven Dampening
Rollers will provide inadequate or uneven water
giving rise to scumming.
wear- A hard dampening
or Plate Inking roller will cause rapid wearing
Size- A hard or glazed
roller gives dot elongation or dot again.
This effects in getting sharp image with full
Due to accumulation of dried ink
film, roller becomes glazed. Glazed
rollers are poor in traction of ink. Thus
when they strike the plate which is having
greater surface speed than a roller a skid is
produced, in turn causing a streak across the
Ink Rollers refusing to hold ink
is called stripping. These are two main
reasons for stripping. There are two main
reasons for stripping. Loss of affinity
for ink in some areas is due to (a) Film of
dried ink on the rollers, (b) Desensitization of
with roughed up sides does not allow full size
printing. Hence accurate setting and
proper inking is not possible on these rollers.
Dampening rollers tend to "bell" at
the edges due to constant pull of the hose on
the edges. The hose tends to shrink while
drying and thus exerts a pull towards the
center. It upsets the pressure and
distribution of water. It causes bowing of
roller and uneven wear of roller.
A roller absorbing ink, cleaning
solvents and chemicals becomes tacky or swollen.
It gives rapid drying of ink. A good
roller should have low ink absorption rate.
These are white spots appearing
in solid image areas. They are caused by
hardened specks of ink, dried gum, dirt etc. and
hamper the print quality.
Repeat- It is a faint
image outline in printed matter caused by poor
ink film recovery on the plate by rollers.
It is an indication of poor ink storage capacity
in the roller.
of Journal ends- This
gives uneven inking, skidding, due to run-out or
excessive play between the journal ends of
bearings of a roller.
TO MAINTAIN YOUR ROLLERS IN TOP CONDITION
should be cleaned thoroughly with a roller wash
especially at the end of every day's work.
This will prolong the life of the roller and
minimize the hardening effect.
the rollers frequently before the ink starts to
dry. Accumulation of dried ink film will
should never be left for long periods in contact
because" flats" can form on the soft
rollers. Moreover if wash-up has not been
completely clean the rollers can stick at
contact points with the risk of pieces being top
of the surface of the roller when the machine is
rollers become useless because of longtime
and/or improper storage. Spare rollers
should be rotated with the rollers on the press,
at least every six months. This acts as a
sort of seasoning, reliving stresses that are
inbuilt in roller. The replaced rollers
should be cleaned thoroughly and after dusting
them with talcum powder and covering them up
with the black or brown paper, should be rested
horizontally on the journals. The
rubberized portion should never contact any
other surface. The storage place should be away
from direct sunlight and heat.
printing smaller jobs on larger machines
printers tend to release ink only to cover the
print area. This causes the sides of the
rollers to run dry generation high temperature
and causing heavy wear on the roller ends due to
fitting the bearings, take care that you do not
bend or damage the journal ends by hammering or
forcing. Check up the journal ends/bearing
seats, sockets and brackets for wear or damage.
the correct technique for mounting the hose on a
Dampening Roller. Excessive force may
damage the roller by tearing the soft roller
from the metal core.
avoid "bulging" or "belling"
of dampening Rollers place a disc/collar of
fibers/plastic, with a slightly smaller diameter
than the rubber, at both rubber ends and then
sew on the hose ends. Any pressure or pull
exerted now will be on the disc and not on the