2. Introduction
Due to the ever increasing demand for quality
products a high quality standard is important
for the circular weft knitting industry. The high
quality standard can be guaranteed by careful
planning, incorporating appropriate quality
assurance ensure and by accurate allocation of
incurred overheads to their origins. Industrial analyses indicate
that product quality can be improved, and defect cost minimized,
by real-time monitoring of the circular knitting process. The
important function of such a concept lies not only in detecting
process interference but also in identifying their sources and
ensuring their quick and cost effective elimination.
3. What is knitting:
Knitting is the process of
manufacturing fabric by
transforming continuous
strands of yarn into a series of
interlocking loops, each row
of such loops hanging from
the one
immediately preceding it. The
basic element of knit fabric
structure is the loop
intermeshed with the loop
adjacent to it on both sides
and above and below it.
4. Circular knitting
Circular knitting or knitting in the round is a form of knitting that creates a
seamless tube. When knitting circularly, the knitting is cast on and the circle of
stitches is joined. Knitting is worked in rounds in a spiral. Originally, circular
knitting was done using a set of four or five double-pointed needles. Later,
circular needles were invented, which can also be used to knit in the round: the
circular needle looks like two short knitting needles connected by a cable
between them.
Longer circular needles can be used to produce narrow tubes of knitting for
socks, mittens, and other items using the Magic Loop technique. Machines also
produce circular knitting; double bed machines can be set up to knit on the
front bed in one direction then the back bed on the return, creating a knitted
tube. Specialized knitting machines for sock-knitting use individual latch-hook
needles to make each stitch in a round frame.
Many types of sweaters are traditionally knit in the round. Planned openings
(arm holes, necks, cardigan fronts) are temporarily knitted with extra stitches,
reinforced if necessary. Then the extra stitches are cut to create the opening,
and are stitched with a sewing machine to prevent unraveling. This technique
is called steeking.
7. Process flow chart of circular knitting machine:
Yarn in package form
↓
Place the yarn package in the creel
↓
Feeding the yarn
↓
Set the m/c as per design & GSM
↓
Knitting
↓
Withdraw the roll fabric and weighting
↓
Roll marking
↓
Inspection
↓
Numbering
8. Types of circular knitting machine:
Circular Knitting Machine
Large diameter circular m/c Small diameter circular m/c
Single Jersey (U.K) Double Jersey (U.S.A) Single Double
Dialand
Cylinder Cylinder
Cylinder
Single tract Multi tract Circular Rib Circular intrlook
Jacquard Non-Jacquard
9. Some circular knitting machine description:
Single Jersey Machines:
Single Jersey machines are
equipped with a single “cylinder”,
about 30 inch diameter, of needles
that produce plain fabrics (single
thickness).Wool production on
single jersey machines tends to be
limited to 20 gauge or coarser, as
these gauges can use two-fold wool
yarns which will give spirality-free
fabrics. An additional inherent
feature of wool single jersey fabrics
is that the fabric edges tend to curl
inwards. This is not a problem
whilst the fabric is in tubular form
but once cut open can become so if
the fabric is not finished correctly.
10. Double jersey machines
Double jersey machines are single
jersey machines with a “dial” which
houses an extra set of needles
positioned horizontally adjacent to the
vertical cylinder needles. This extra set
of needles allows the production of
fabrics that are twice as thick as single
jersey fabrics.
Typical examples include interlock
based structures for underwear/base
layer garments and 1 x 1 rib fabrics for
leggings and outerwear products. Much
finer yarns can be used as singles yarns
do not present a problem for double
jersey knitted fabrics as the “double
layer” construction works to cancel out
the residual torque between the face
and reverse sides, the net effect being
no spirality.
11. Rib circular knitting machine.
In a dial cylinder rib machine there is one set
of needles on the circumference of the
vertical cylinder and another set of needles on
a horizontal dial. So two sets of needles
remain at the right angle with each other. In
dial cylinder machines the dial and cylinder
rotates but the cam systems with the feeders
remain stationary.
The dial needles get its motion from its butt
which is placed on the cam truck. This cam
truck is formed by different cam placed on a
cam plate.
During the rotation of the cylinder, cylinder
needles moves vertically and dial needles
moves horizontally. Cylinder needles also get
its motion from it. There is a cloth tale up
roller which also rotates with unison to dial
and cylinder and fabric is wound on it.
12. Knitting action:
The knitting action of a circular rib machine is shown:
1. Clearing: The cylinder and dial needles move out to clear
the plain and rib loops formed in the previous cycle.
2. Yarn feeding: The needles are withdrawn into their tricks
so that the old loops are covered by the open latches and the
new yarn is fed into the open hooks.
3. Knocking Over: The needles are withdrawn into their
tricks so that the old loops are cast off and new loops are
drawn through them.
13. Interlock circular knitting machine:
The yarn is supplied from cone, placed either on an integral over
head bobbin stand or one free standing creel through tensioners
stop motion & guide eyes down to the yarn feeder guides.
The fabrics is tube form is drawn downwards from inside the
needle cylinder by tension rollers & is wound on to the fabric
batching roller of winding down fabrics.
The winding down mechanism revolves in unison with the
cylinder & fabrics tube & in rock lever operated via cam followers
running on the underside of a profiled cam - ring.
The sinker cam plate is mounted outside on the needle circle, the
center of the cylinder is referred to as an open top or sinker top
m/c.
14. Knitting action:
The knitting cycle of a interlock machine can be
divided in to eight headings. They are discussed below,
• Position – 1: Rest position: The head of these needles
are in the range of the knock over edges of cylinder &
dial respectively.
• Position – 2: Tucking position of dial needle: The dial
needles are brought into the tucking position.
• Position – 3: Tucking position: The cylinder needles
are brought in the tucking position.
15. Knitting action:
• Position – 4: Clearing position of dial needle: The dial
needles are come into the clearing position.
• Position – 5: Clearing position: The cylinder needle are
come into the clearing position.
• Position – 6: Yarn presenting position: Both cylinder & dial
are moved to the yarn presenting position.
• Position – 7: Cast on position: Both cylinder & dial are
moved to their cast on position.
• Position – 8: Knock over position: Both cylinder & dial are
reaches to the knock over position.
16. Features of circular knitting machine:
1. Frame: The frame, normally free-
standing and either circular or rectilinear
according to needle bed shape, provides
the support for the majority of the
machines mechanisms.
2. Power supply: The machine control
and drive system co-ordinates the power
for the Drive of the devices and
mechanisms.
3. Yarn supply or feeding: The yarn
supply consists of the yarn package or
beam accommodation, tensioning
devices, yarn feed control and yarn feed
carriers or guides.
17. Features of circular knitting machine:
4. Knitting action: The knitting system includes the
knitting elements, their housing, drive and control, as
well as associated pattern selection and garment-
length control devices (if equipped).
5. Fabric Take-away: The fabric take away
mechanism includes fabric tensioning, windup and
accommodation devices.
6. Quality control: The quality control system
includes stop motions, fault detectors, automatic oilers
and lint removal systems.
19. Advantages of circular knitting machine:
Less load by high precision
Perfect gaps between all
parts.
Smooth passing of Needles
between cylinder and cams
better quality of plated
fabric
Less friction for each part
Longer needle’s life
Save power consumption
Fantastic Machine Speed
Awesome Specification of
Rib
Immediate restart after
Setting
Save Maintenance Cost
Life time guaranty of
Ceramic yarn carrier.
Longer needle life
Special servomotor for
take-up system
20. Conclusion:
Modern circular knitting machines feature on-board computers
(CPU) complete with a display and a keyboard to monitor and
control the most important functions:
Speed
Number of machine revolutions (R.P.M)
Working hours
Causes of machine stops
Detector of the yarn length fed into the machine
On modern microprocessor-controlled machines, the LCD display
(TOUCH SCREEN) is equipped with an alphanumeric keyboard
for entering the operator’s settings. The whole system is
controlled by an electronic circuit which signals the status of the
machine and the possible causes of machine stops by means of
flashing lights.
