Circular Knitting Machine:
Circular knitting machine is a knitting machine that knits a fabric tube. This machine makes knitting so easy. The term circular covers all those weft knitting machines whose needle beds are arranged in circular cylinders and dials, including latch, spring bearded and very occasionally compound needle machinery, producing a wide range of fabric structures, garments, hosiery and other articles in a variety of diameters and machine gauges. Circular knitting machine came in the market around 1850.
Features of a Circular Knitting Machine:
The common features of a circular knitting machine as follows:
- Circular knitting machine normally has rotating (clockwise) cylindrical needle bed (s).
- On circular knitting machines latch and compound needles are used. One seldom finds bearded needles or other needle types. Normally one or two sets of Latch needles are used.
- For single-jersey machine holding down sinkers are used, one between every needle space.
- Normally stationary angular cam systems are used for needle and sinker.
- Latch needle cylinder and sinker ring (for single-jersey machine) I dial (for double jersey rib and interlock machine) revolve through the stationary knitting cam system.
- For single-jersey machine, sinker trick ring which is simply and directly attached to the outside top of the needle cylinder thus causing the sinkers to revolve in unison with the needles.
- Needle retaining spring is also used
- Stationary yarn feeders are situated at regular intervals around the circumference of the rotating cylinder.
- Yarn is supplied from cones, placed either on an integral overhead bobbin stand or on a freestanding creel through tensioners, stop motions and yarn guide eyes down to the yarn feeder guides.
- Yarn feeder guide which is associated with its own set of knitting cams.
- Machine gauge is normally used 5 to 40 needles per inch and machine diameter up to 30 inches. Up to 60 inch diameter machines are now available.
The following features of a modern circular fabric producing machine that ensure that high quality fabric is knitted at speed with the minimum of supervision:
- The top and bottom stop motions are spring-loaded yarn supports that pivot downwards when the yarn end breaks or its tension is increased. This action releases the surplus yarn to the feeder, thus preventing a press-off, and simultaneously completes a circuit which stops the machine and illuminates an indicator warning light.
- Various spring-loaded detector points are carefully positioned around the cylinder according to their particular function. A pointer is tripped to stop the machine by a fault or malfunctioning element such as a yarn stub, fabric lump, needle head, latch spoon etc.
- The tape positive feed provides three different speeds (course lengths) and is driven and can be adjusted from the drive arrangement.
- The cylinder needle cam system for each feed is contained in a single replaceable section and having an exterior adjustment for the stitch cam slide.
- The automatic lubrication system.
- Start, stop and inching buttons.
- The cam-driven fabric winding down mechanism, which revolves with the fabric tube.
- The revolution counters for each of the three shifts and a pre-set counter for stopping the machine on completion of a specific fabric length (in courses).
- Normally side creel is used.
- Lint blower is used. This reduces the incidence of knitted-in lint slubs, to improve quality when using open-end spun yarns. It also reduces cross-contamination by fibers from other machines.
Process Flow Chart of Circular Knitting Machine:
Yarn in package form
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Place the yarn package in the creel
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Feeding the yarn
↓
Set the m/c as per design and GSM
↓
↓
Withdraw the roll fabric and weighting
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Roll marking
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Inspection
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Numbering
Classification of Circular Knitting Machines:
There are many types of circular knitting machine that produce long lengths of tubular fabric manufactured for specific end uses. Mainly three types of circular knitting machines are classified below.
a) Revolving cylinder latch needle machines:
They produce most weft knitted fabrics. They are of two main types –
- Open top or Sinker top or Single jersey machines
- Dial and cylinder machine
Both have the following features in common:
- Open top machines have one set of needles usually arranged in the cylinder.
- Except in the case of certain effect fabric machines such as pelerine, cylinder and dial machines are of either the rib or interlock type.
- Machines of both types may or may not have patterning capabilities.
b) Revolving cylinder bearded needle single-jersey fabric machine:
There are two types of circular bearded needle single-jersey fabric machines still manufactured,
- The Sinker Wheel machine or French or Terrot type machine.
- The Loop wheel frame or English type machine.
Both have the following features in common:
- Needles are fixed in needle bed.
- Revolving needle bed
- Ancillary elements moving yarn and loops along the needle stems.
- Fabric tube knitted with its technical back facing outwards.
- Less number of feeders accommodates.
- Comparatively low productivity compensated by an ability to produce unusual and superior quality knitted structures.
c) Circular garment length machines:
- They are generally of body-width size or larger having a cylinder and dial arrangement or a double cylinder.
- They are of the small-diameter hosiery type with either a single cylinder, a cylinder and dial or double cylinders.
Uses of Circular Knitting Machine:
- Fabric machines: Rolls of fabric with the following end-uses: jackets, ladies’ tops, sports and T-shirts, casual wear, suits, dresses, swimwear, bath robes, dressing gowns, track suits, jogging suits, furnishing, upholstery, automotive and technical fabrics, household fabrics.
- Garment blank machines: Underwear, T-shirts, jumpers, pullovers, cardigans, dresses, suits, trouser suits, vests, briefs, thermal wear, cleaning cloths, technical fabrics.
- Hose machines: Seamless hose, tights, industrial use dye bags, knit-de-knit yarns, industrial fabrics.
- Half-hose machines: Men’s and boy’s half-hose, ladies’ stockings, children’s tights sports socks.
Circular knitting machines with very small diameters are useful to produce textile implants for medical applications, such as oesophagus, stents, and so on.
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
- Less maintenance cost
- Life time guaranty of ceramic yarn carrier.
- Longer needle life
- Special servomotor for take-up system
Conclusion:
Circular knitting machine a common machine used in knit garment manufacturing industry that can produce fabric at a lower price. Circular knitting machines can produce Single jersey fabric, double-jersey fabric, rib fabric, interlock, and jacquard fabrics. This machine is extremely productive and can produce large quantities of small knitted fabrics. It can produce seamless tubular fabrics with precision and minimal waste makes them ideal for manufacturing garments like T-shirts, socks, and underwear.
References:
- Understanding Textile for a Merchandiser by Engr. Shah Alimuzzaman Belal
- Fundamentals and Advances in Knitting Technology by Sadhan C. Ray
- Advances in Knitting Technology Edited by K. F. Au
- Knitting Technology, 3rd Edition by David J Spencer
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