The principal feature of garments made from knitted fabric is that the nature of the final garment and the processing it goes through are affected in a major way by the primary knitting process. It is possible to have four knitted garments which look superficially similar but have been produced by four differing processes (Fig. 1.1). This chapter defines these processes and discusses the relative methods and use of them.
All knitted garments can be classified into four categories according to general production methods:
(1)
fully cut;
(2)
stitch shaped cut;
(3)
fully fashioned;
(4)
integral.
Fully cut (Fig. 1.2)
The term 'fully cut' describes the processes most akin to making garments from woven fabric. Garments are cut from piece goods fabric, laid up (spread) on to cutting tables. All parts of the garments other than the trims are cut from the ray. Each garment piece has all edges cut, hence the term fully cut.
The garments are assembled by seaming machines, often of a specialist nature, and trims are added where appropriate. The fabric for this process is invariably knitted on circular knitting machines. Such machines come in a wide range of types but are mostly classified under two headings:
(1)
single jersey or plain web machine;
(2)
double jersey or rib machine.
FULLY CUT GARMENTS , PRODUCTION SEQUENCE.
Circular knitting of fabric
↓
Scouring, bleaching and/or dyeing
↓
Pressing, calendering or decatizing
or stentering
↓
Laying up (spreading) of fabric
↓
Marking and cutting
↓
Assembly
↓
Examine and mend
↓
Finish press
Fig. 1.2 Production sequence of fully cut garments
These machines vary in diameter, the number of needles per inch/ centimetre (gauge), the number of courses they can knit in one revolution (number of feeders), and their fabric patterning capabilities. Modern circular machines are capable of extremely high production rates (300 m2/hour).
The fabric varies according to the type of garment to be made and the knitting machinery is usually designed specifically for a particular class of garment: specialist sports clothes and leisure activity clothes, jersey dresses, suits, slacks and other outerwear. Exceptionally 'knitwear' is sometimes produced.
As already suggested, fully cut is analogous to the processing of woven fabrics but there is one important distinction that influences the whole range of processing. All knitted fabrics and the garments made from them are extensible. Care must be taken with the wet and dry finishing processes to avoid stretching and thus inducing shrinkage potential into the fabric. Care must also be taken with laying up, cutting and finally the making up processes, to avoid distortions.
Making up of the garments is usually carried out with a three thread overlock stitch (BS stitch type 504), although multi thread chain stitch seams are increasingly being used on underwear, swimwear and leisure-wear.
CUT STITCH- SHAPED GARMENTS,
flat or circular knitting of blanks
↓
rough press
↓
cutting
↓
assembly
↓
examine and mend
↓
finish press
Fig. 1.3 Production sequence of cut stitch-shaped garments
Sewing machine attachments are of major importance for speeding work times. There are general and specific attachments to seaming machines for hemming, binding, elasticating and other seam forms.
The attractions of fully cut processes are:
(1) the relatively low costs of the fabric produced at high speeds with low labour input;
(2) the opportunity for scale of production which particularly shows benefits at the cutting stage.
The disadvantages are:
(1) the relatively high waste factors that occur even with small garment pieces. Such wastage ranges from 17% to 50% and is a significant cost burden on the garments produced;
(2) the high labour cost of assembly of the garment.
Cut stitch shaped (Fig. 1.3)
The majority of knitwear is produced by this method, together with a very small production of ladies vests. The general method involves knitting rectangles of fabric relating to the size of the portions of the garment to be made. The pieces, known as 'blanks', have the lower edge of the fabric sealed with a structure known as a 'welt' that prevents laddering and distortions of waistbands and cuffs.
The term 'stitch shaped' derives from different stitch structures within the length of the blank that distort it from the rectangle into a shape associated with the human body. Commonly such shaping involves engineered rib waistbands and cuffs that restrict the lower extremity of the garment but are extensible. In ladies vests such waistbands Occur in the middle of the garment blank.
These blanks require minimal preparation for seaming. Cutting involves trimming for length and sometimes for width, followed by cutting neckholes and armholes, lower arms and shoulder shaping.Cutting is still largely carried out by hand, using shears on individual or doubled pieces. Template press cutters capable of dealing with up eight blanks at a time are also employed. Such labour intensive operations are offset by the low wastage figures achieved — 10-20%.
It pays to make the blank as near as possible to the exact size of the garment portion, or a width multiple of the garment portions. The knitting machinery employed to produce the blanks is in its mechanised form the most complex of all, although it must he admitted that simple hand flat knitting machines can produce highly complex blanks, with the `programme' being in the brain of the operative.
There are two types of knitting machine employed: flat and circular. Both are usually rib machines, with two knitting beds and two sets of needles. Some are purl type, with two beds sharing one set of needles. Flat knitting machines knit blanks with selvedges on the side of the fabric. The blank can be any width up to the total width of the machine bed. Two or more blanks can be knitted at the same time.
Flat machines are relatively slow and even with five knitting systems the most advanced machinery makes very few blanks in an hour — 24 maximum and 12 normally. The labour of machine minding and the high capital cost of the machines feature significantly in the cost of a garment.
Flat machines vary in their complexity with the simple types being used for relatively simple garments. Most machines now are computer controlled and programmed and are built for prodigious versatility of fabric type and patterning. Other mechanical developments of this type of machinery also allow the production of fully fashioned and integral garments, although at the expense of the production rate.
The circular machines produce blanks in the form of tubes, the circumference of the tube being related to the diameter of the machine. A particular size of tube may be used to produce a certain size of garment, with minimal waste on the side seams. Various diameters of machines are assembled in a plant to produce a range of garment sizes.
Production management of such a plant is extremely difficult as changes of structure in the fabric of the blanks change the circumference of the fabric produced. An 18 in diameter machine may produce a 44 in (112 cm) width of one fabric type and a 38 in (96 cm) width of another. Inevitably either some of the plant remains idle or the plant is fully employed with added wastage of raw materials when cutting small garments from large blanks.
The approach now employed to minimise the problems is to have very large diameter machines producing large circumference tubes that are split down the side, opened out and cut into a series of
and sleeves to fit the production requirements and mini f widths mise waste. Such bodies a
machine is the Jumberca TLJ-5E, produced in a diameter of 33 in and producing fabrics from 2.5 m to 3 m wide.
Yet a further approach is the variable circumference machine. This type still knits in a continuous revolving manner but some of the needles around the circumference do not knit. The number of these can vary and they are situated in a block on either side of a space 60° in circumference, that contains no needles. In each revolution of the machine, yarn is cut and trapped when it reaches the gap and knitting recommences on the other side of the gap. Thus the fabric is produced not as a circle but as an open width blank, the width of which can be varied to suit the production requirements, with minimal waste. The patents for this machine type are held by Mecmor who produce the Varitex garment length machine, TEJ 180, with a 33 in diameter and 12 feeders, and the TEJ 2500 with a diameter of 40 in (101 cm), 18 feeders and a maximum knitting width of 110 in (280 cm).
Like the flat machines, circular garment length machines have been subject to electronic development; computer controls have been fitted to them to handle the complexity of information required to knit a garment blank. Separate programming computers with a Computer Aided Design (CAD) facility are used to produce the tape or disk that is 'read' by the knitting machine.
The garments are assembled almost entirely by the .use of three and four thread overlock machines (BS stitch types 504 and 506). Seam covering stitches (BS 602) are sometimes used on the facings or 'stoning' of cardigan and back neck seams. Collars are often attached by linked, or increasingly, mock linked seams (BS 101 or 401). Lockstitch seams are used when attaching inextensible trims such as ribbon facings, plackets, leather and woven fabric decorative portions, and tabs and labels.
Often, in the initial stages of production prior to cutting, the blanks are steamed on an open bed — in the case of acrylics — or pressed — in the case of wool and cotton. To facilitate ease of handling and maintenance of size, two similar blanks are often seamed together temporarily with chain stitch before the steaming. Heavy, rectangular, wire frames are sometimes used to. hold the blanks to prescribed dimensions.
Fully fashioned (Fig. 1.4)
Fully fashioning is the process whereby portions of a garment are shaped at the selvedges by progressively increasing or decreasing the number of loops in the width of the fabric. Such narrowing and widening produces the shape of a piece of garment that would otherwise be generated by
cutting.
FULLY FASHIONED GARMENTS, PRODUCTION SEQUENCE
Knitting ribs and garment portions
↓
Rough assembly
↓
Scour, dye, mill, shrink-resist finish
↓
Press
↓
Cut, neckholes etc.
↓
Attach collar
↓
Examine and mend
↓
Finish press
Fig. 1.4 Production sequence of fully fashioned garments.
Fashioning has two obvious advantages over the two previously described categories of garment making:
(1)
there is little or no cutting waste;
(2)
the edges of the garment pieces are sealed and not liable to fraying, so can be joined by simple non-bulky seams.
Fully fashioned garments are usually associated with knitted outerwear of a particular classical type and with a particular type of machinery: the `straight bar' or 'Cotton's Patent' knitting machine. However, knitted underwear is made on a fully fashioned basis, although the quantity is now very small compared to that made in the 19th century. A similar situation applies to ladies hose which suffered a dramatic eclipse in the early 1960s when a fashion change wiped out an enormous industry virtually overnight.
Men's heavy rib sweaters are also fully fashioned on hand flat knitting machines, as are fine gauge ladies suits and dresses.
Increasingly the fashioning capabilities of modern electronically con¬trolled V-bed flat machines are being used for making fully fashioned garments with scope for embellishment using a wide range of patternings. Such a use, with savings of material and making up costs, Will increasingly feature as a development of the stitch shaped industry.
INTEGRAL GARMENT (1/2-HOSE) PRODUCTION SEQUENCE
Knit half hose
↓
Seam toes
↓
Wet finish, scour, dye
↓
Examine and mend
↓
Finish press, set
Fig. 1.5 Production sequence of integral garment (half hose).
Making up traditional classical fully fashioned garments takes place in two stages:
(1)
rough making up;
(2)
finished making.
The rough making up is carried out to join the basic portions of the garment together: front, back and sleeves along the selvedge. Cup seamers are used to provide a single or double chain stitch for these seams. With some styles — saddle shoulders and set-in sleeve jumpers — linking is used to join the shoulder seams, loop for loop.
The rough made up garment can at this stage be wet processed. This is carried out on the majority of garments that are single coloured, and on some that are multi-coloured. Wet processing involves some or all of the following: scouring, milling, shrink resist and dyeing.
After drying, hoarding and pressing the finishing making up is carried out, including cutting of necklines, fronts of cardigans and shirts, attaching collars, facings, stollings and buttons, buttonholing etc. Linkers, mock linkers and lockstitch machinery are used.
Fully fashioned garments made on V-bed machinery are not normally wet processed, and making up is usually by cup seamers, linkers and mock linkers.
Integral garments (Fig. 1.5)
Integrally knitted garments are those that are essentially knitted in one piece with little or no seam. The archetypal example is the beret, which is knitted sequentially in a series of triangles, leaving the beginning and the end to be joined into a three dimensional shape. This principle has also been used to make skirts and jumpers and is used to produce a large proportion of ladies and gents millinery.
Another integral garment using a combination of tubular knitting and shaping is the men's sock or half hose. To shape the heel and toe of a sock, pouches are formed from extra rows of knitting.
The third common type of integral garment consists principally of joined tubes — the glove. Tubes are constructed for each of the digits, sometimes with shaped tips, and merge together into the palm portion, (also a tube). Such gloves can now he knitted fully automatically (Shim, Seiki) with no subsequent making up procedures.
Integral concepts are proposed from time to time for upper body outer-wear garments, and have been the subject of patents. Inhibitory factors to their introduction include lack of competent designers and development technicians, and sheer conservatism on the part of producers.
The rewards could be considerable, saving both raw material anti labour costs at the expense of lower machine output. There is little question that the electronic V-bed knitting machines in their present state of development, with presser foot or holding sinkers, are easily capable of producing garments in all the integral garment categories.