ROLLER PRINTING

 Printing can also be defined as localized
dyeing.
 Roller printing, also called cylinder printing
or machine printing, on fabrics is a textile
printing process.
 Invented by : Thomas Bell of Scotland in
1783.
 It is a modern continuous printing
technique.
 This was introduced in an attempt to
reduce the cost of the earlier copperplate
printing.

 In this machine counterpart of block
printing, engraved Cu cylinders or rollers
are used in place of hand carved blocks.
 In this method, a heavy copper cylinder
(roller) is engraved with the print design
by carving the design into the copper.
 Copper is soft, so once the design is
engraved, the roller is electroplated with
chrome for durability.

Roller-printed cotton cushion cover
panel , 1904

ENGRAVED COPPERPLATE
PRINTING
The printing of textiles from engraved copperplates
was first practiced by Bell in 1770.
It was entirely obsolete.
The presses first used were of the ordinary
letterpress type, the engraved plate being fixed in
the place of the type.
In later improvements the well-known cylinder
press was employed; the plate was inked
mechanically and cleaned off by passing under a
sharp blade of steel; and the cloth, instead of
being laid on the plate, was passed round the
pressure cylinder.

The plate was raised into frictional contact with
the cylinder and in passing under it transferred
its ink to the cloth.
The great difficulty in plate printing was to
make the various impressions join up exactly;
and, as this could never be done with any
certainty, the process was eventually confined
to patterns complete in one repeat, such as
handkerchiefs, or those made up of widely
separated objects in which no repeat is visible,
like, for instance, patterns composed of little
sprays, spots

It gives higher production without
rotary screen printing machine.14 colors
can be used for printing.
Even Medium designs can be produced.
It can be used for printing any style.
 Any color is used for printing without
higher alkali or conc. acid.
Higher production by using single color.
Complex design is possible.

OPERATION
 This machine has a main cylinder that is
fitted with a large gear. In this printing,
the print paste is supplied from reservoirs
to rotating copper rollers, which are
engraved with the desired design.
 These rollers contact a main cylinder roller
that transports the fabric. By contacting
the rollers and the fabric, the design is
transferred to the fabric.

 ENGRAVED ROLLERS
 Solid and shell engraved rollers are available
which varies in length.
 When the copper engraved rollers are
chromium or nickel plated their lives can be
considerably lengthened.

 As many as 16 rollers can be available per
print machine, each roller imprints one repeat
of the design.
 As the roller spins, a doctor blade in
continuous mode scrapes the excess of paste
back to the color trough.

 DOCTOR BLADES :
Color doctor :- color doctor is made of steel.
 It consists of a sharp steel blade and has a razor
like edge, which rests on the engraved roller.
 The other edge is clamped between two brass
plates and screwed together.
 The doctor blade is given a to and fro motion
parallel to the direction of the roller axis to
prevent unequal wear and tear of the blade edge
which is done by the transverse motion.

 At the end of each batch the paste reservoirs
are manually emptied into appropriate printing
paste batch containers and squeezed out.
 The belt and the printing gear (roller brushes
or doctor blades, squeegees and ladles) are
cleaned up with water.

LINT DOCTOR:
 The lint doctor is made of brass
 No transverse motion is imparted to it.
 It’s purpose is to pick up loose cotton fibers attached to
the engraved roller, which otherwise would find their
way into the printing paste in the color box.
 LAPPING:
 This is covering of the central pressure bowl and is
made up of a special fabric of linen warp and worsted
weft.
 Eight to twelve layers of the fabric are wound on the
bowl to free from creases.

BLANKET:
 It is a thick woollen cloth tightly woven and
felted.
 It is of uniform texture , elasticity and of equal
thickness.
 This increases the elasticity of the lapping and it
circulates continuously round the pressure bowl
between the lapping and cloth to be printed.
 After continuous use the blanket becomes hard and
soiled by the paste penetrating into it and must be
either turned or replaced.

BACK GREY:
 When the woolen blanket is used unbleached cotton
cloth is run between the blanket and the cloth to be
printed protects the blanket from the paste passing
through the cloth.
 It is not necessary when the washing blanket is
employed .
 It is wound on a roller and after printing it leaves the
machine and is wound again on another roller.
 After use it is taken for bleaching and may be used
for printing.

DEFECTS
SCRATCHES :
When grit particles in the printing paste cut
the smooth surface of the roller, the
scratches produced will also transfer the
paste to the cloth. By burnishing ( polishing)
the roller as well as by staining ( filtering)
the printing paste , the fault can be
removed.

SNAPPERS :
Loose threads from the cloth escaping under
the lint doctor , bits of the dried up paste and
other hard particles cause snappers, which are
large doubled stripes of color running along the
length of the cloth. A larger amount of paste
is transferred to the fabric . This defect can
be prevented by washing and cleaning the
doctor blade , roller and by staining the paste.

LITTS :
Very minute snappers called litts are produced at
regular intervals on the cloth. These are caused by
hard particles like a metal piece getting embedded in
the engraving of the roller and protruding from it ,
there by lifting the doctor blade temporarily.
STREAKS:
Streaks are very fine lines or series of lines running
along the piece and parallel to selvedges.These may be
due to scratches on the engraved roller or a cut in the
doctor blade edge.Polishing the roller and sharpening
the doctor blade edge are the remedial measures to be
taken.

SCUMMING:
Spoiling of the by one or more colours due to
insufficient scrapping of the print paste from the
engraved portion . It can be due to:
* Rough Doctor Blade Edge
* Badly Adjusted Engraved Roller
* Defective Printing Paste
SCRIMP:
Creases , which are remaining in the cloth while
printing give rise to the defect of non printing
underneath the fold.

UNEVEN PRINTING:
Uneven pressure due to faulty lapping or improper
feed of the print paste ,too much polishing of
certain parts to eliminate scratches ,give uneven
impressions
LOBBYING:
This is an uneven printing due to slippage of a
roller round its mandrel, due to improper fitting .
BACK-GREY CREASE:
This defect is caused due to improper feeding of
fresh back-grey, inefficient washing and
improper drying of used back grey .

BACK-GREY STITCH IMPRESSIONS :
Although this is an inevitable defect because of
the stitch impressions, it can be minimized by
using the suitable sewing thread.

ADVANTAGES.
 Higher production without rotary screen printing
machine.
 14 colors can be used for printing.
 Medium design can be produced.
 Can be used for printing any style.
 Any color is used for printing without higher
alkali or conc. acid.
 Higher production by using single color.
 Complex design is possible.

DISADVANTAGES.
 Large design is not possible.
 Higher coloring effect is not possible as like
block printing.
 Lower production by using more than one
color.
 Changing time is high.
 Engraving the printing roller is expensive
Operation.