Home-immediately access 800+ free online publications. Download CD3WD (680 Megabytes) and distribute it to the 3rd World. CD3WD is a 3rd World Development private-sector initiative, mastered by Software Developer Alex Weir and hosted by GNUveau_Networks (From globally distributed organizations, to supercomputers, to a small home server, if it's Linux, we know it.)ar.cn.de.en.es.fr.id.it.ph.po.ru.sw

CLOSE THIS BOOKSmall-Scale Weaving (ILO - WEP, 1983, 144 p.)
CHAPTER II. PRODUCTION OF WARPS AND PIRNS
VIEW THE DOCUMENT(introduction...)
VIEW THE DOCUMENTI. Production of warps
VIEW THE DOCUMENTII. Production of pirns

Small-Scale Weaving (ILO - WEP, 1983, 144 p.)

CHAPTER II. PRODUCTION OF WARPS AND PIRNS

The various factors to be taken into account in warp preparation and in weft-pirning are considered in this chapter in relation to the selected scales of production.

I. Production of warps

I.1 Warp preparation for small-scale weaving units

Fabrics of the type considered in this memorandum are difficult to produce as they require stringent warp preparation and looming to ensure satisfactory weaving with a minimum of thread breakages at the given production rates. A number of warping techniques are described below.

(a) Manual methods of warp preparation

Traditional manual methods of warp preparation are unsuitable for production rates that may be expected from even a small mill. The principal reasons for this are:

(i) Warp lengths considerably greater than those normally produced for hand-loom weaving of speciality cloths are necessary in order to obtain the requisite scale of production; and

(ii) the warp must not contain crossed ends and all threads require to be wound at similar uniform tension from start to end of the beam. These objectives cannot be readily attained by manual preparation methods without increasing costs in a prohibitive manner. If, therefore, hand-loom weaving is to be seriously considered it must be realised that it is only likely to be a viable proposition for the cloths under consideration if means of mechanical warp preparation are included. Possibly, a separate organisation, located close enough to the weaving production units, could prepare loom warps for a number of small weaving establishments. Assuming, therefore, that some external organisation prepares the warps, warp preparation may be undertaken according to the following two methods.

(b) Warping from back seams

This is by far the most common method which is appropriate to the types of fabric considered. The method itself is described in more detail under the section dealing with medium- and large-scale weaving. It should be pointed out here that the use of the system for relatively short hand loom warps will involve additional operations, e.g. an additional warp-cutting and rebeaming operation following the normal winding-on to the weavers’ beam after sizing. The reason for these extra operations is to avoid overdrying and consequent damage to the yarn by frequent stoppages during the sizing process. Warp-sizing is a necessary preliminary process to weaving for most cotton-type warps in order to minimise warp thread breakages in the loom. The sizing process is dealt with later in this chapter.

(c) Scotch Beaming and Dry Taping

The second possible method of warp preparation is the system used mainly for colour-stripe warps known as Scotch Beaming and Dry Taping. In this system, the loom warp is built up from a number of sections, with each section prepared separately, in either ball, chain or cheese form, from the requisite number of individual yarn packages. These packages are mounted in a creel behind a modified form of beam-warping frame having the necessary winding mechanism. The ball warps, which may then be dyed or left in grey form as required, are next run through a size bath and dried. After drying, each ball warp is run on to a separate back beam as an open sheet similar in width to that of the final weavers’ warp. The open-sheet form is achieved by passing the rope of threads over grooved rods, which cause some preliminary opening-out, then through a reed and finally through an expanding comb which guides the sheet on to the back beam. The back beams made from all the warp sections are next mounted in a creel at the dry-taping frame. From this creel, the sheets are unwound together and superimposed to form a single sheet of the required final thread density; this sheet is then wound on to a loom beam at the frame headstock. Warps of any desired length can be prepared in this manner. However, for grey warps, the system has no real advantage over the previous back beam method, and is certainly much slower. It is, however, one method by which self-coloured warps for denim cloths (e.g. T1 fabric) can be prepared.

If the warps have to be prepared at the hand-weaving factory, the situation becomes more difficult in view of the much smaller scale of operations while the sizing of yarn is still necessary. One method to be considered would be to first size the yarn in hank form. This will require means for pre-boiling the yarn to improve size pick-up and also, after sizing and before drying, further means for mechanical shaking, stretching and brushing of the hanks. The sized yarns will next have to be wound on to bobbins, or cone-wound, and the packages placed in a creel of suitable form from which the yarns can be withdrawn to make back beams for later dry-taping on to loom beams, in a similar manner to that already described. An alternative to dry-taping is to prepare the loom beams from warp sections wound side by side on a horizontal sectional warping mill, the yarns having first been hank-sized and coned as before. All warp sections on the mill are later re-wound as a single sheet from the mill on to weavers’ beams (see ‘Indirect warping system’ in Section I.2 (b)).

(d) Shirley Miniplus Method

Should neither of the above hank sizing systems be suitable, and if loom warps of only 11 metres nominal length will suffice, consideration might be given to a unit designed primarily for the preparation of sized sample warps known as the Shirley Miniplus. The Miniplus is made by Sellars + Company (Huddersfield) Ltd. Warps are made on this machine from either a single yarn package, such as a cone or hank, or from yarns from two packages which are run simultaneously side by side. As the yarn unwinds from the supply package(s) it passes through a trough containing size paste and afterwards through a heated chamber to dry the size picked up by the yarn. On leaving the drying chamber, the yarn is wound as a continuous spiral(s) across the width of a large rotating reel or swift of 11 metres (12 yd) circumference. The number of coils run on to the reel equals the number of threads required in a loom warp of 91 cm (36 in) width. After winding on the coils, the reel is stopped and adhesive tapes and clamps are put across the coils at two adjacent circumferential points on the reel in order to secure the coils in sheet form. The coils are then cut between the clamping points, thus enabling the sheet of yarns so formed to be unwound from the reel and re-wound on to a loom beam.

The speed of warp preparation by the Miniplus method is directly dependant on the rate at which the sized yarn can be dried and on whether the warp is prepared from a single yarn package or from two packages winding-on simultaneously. For yarns of 48 Tex (12Ne) (for weaving cloth (P1)) wound-on from two packages at an average reel speed of 4.5 rev/min, the time to wind 1488 coils for a cloth 91 cm wide (+ 32 additional threads for selvedges) would be approximately 166 minutes for the sizing and winding operations only. Furthermore, time must be added to prepare the size and to wind the warp from the reel on to the loom beam; the latter operation usually takes between 20 and 30 minutes. If, however, the warp were to contain many more threads of finer yarn, such as cloth (P4) which, including extra ends for selvedges, would contain around 3441 ends of 12 Tex (48Ne) yarn in a width of 91 cm, the time to size and reel-on would be nominally 246 min if the reel were run at 7 rev/min. This higher reel speed is the result of a shorter time needed to dry the finer yarns in this cloth. The drying chamber temperature has been assumed to be the same in both instances (i.e. approximately 90°C).

Other machines for preparing sample warps have been made to meet specific requirements. One of these, made by Hergeth KG (4408 Dulmen, Federal Republic of Germany), is well-known. It is a much more sophisticated and expensive machine than the Miniplus. While it has electronic control facilities which make it reasonably simple to operate, it will undoubtedly require a high level of technical knowledge to maintain and service. For this reason, and that of high cost, its adoption by small-scale weavers may not always be justified.

I.2 Warp preparation for Medium and Large-scale weaving units

There are two principal methods of warp preparation for cotton and man-made fibre fabrics, viz. ‘Direct’ or warping from back beams, and ‘Indirect’ or section warping.

(a) Direct warping

This method is most suited to the production of warps for the types of fabrics covered by this memorandum. The system consists of producing first a number of separate back beams, called a set. All back beams in a set contain roughly the same number of threads (ends): this number is such that when later all the individual sheets from these beams are superimposed and combined they form a single warp sheet containing the total required ends in the weavers’ warp. It may be noted that all the individual threads from any single back beam are approximately evenly distributed across the width of the finished warp. The upper limit to the number of ends on a back beam is determined largely by the size of creel in which the cones of yarn are held for making the beam. A creel capacity of between 500 and 512 cones is very common. Thus, for a warp for cloth (P1), which for a fabric 100 cm width requires approximately 1632 ends (inclusive of selvedges) on the loom beam, four back beams might be made, each containing 408 ends of 48 Tex (12Ne) yarn. Similarly, for a warp for cloth (P4), with a total of 3776 ends of 12 Tex (50Ne) yarn and 100 cm width, eight back beams, each of 472 ends, could be made.

The warp length on a back beam is usually sufficient to make a number of loom beams when the sheets from all beams in a set have been later combined during the warp sizing operation which follows beaming. Let us suppose that, in the case of cloth (P1), each loom warp must be of sufficient length to weave 1000 metres of fabric. After making allowances for warp crimp and for waste in sizing and weaving (up to a total of around 10%), the length of warp to be wound on to each back beam in the set would be 1000 x 1.1 x 8 = 8800 metres (i.e. sufficient length to produce 8 weavers’ warps). This length can be accommodated on a standard size of back beam of 711 mm (28 in) flange diam. x 1380 mm (54 in) width between flanges, with the yarn wound at medium pressure so as to obtain a firm but not too hard a beam. The cutting of the sized warp to length takes place as the warp is being wound on to the weavers’ beams at the headstock of the sizing machine.

Beaming machines

Beam-warping machines are of two types: indirect beam-drive (drum-drive) and direct spindle drive. Although either machine can be used for cotton type warps, the former are generally less expensive and require less maintenance than the latter, which were primarily designed for the high-speed warping of continuous filament yarns. In drum-drive machines, the warp beam is driven by frictional contact with a large rotating drum at recommended speeds, for spun yarns, which do not usually exceed 450 metres/min. However, for the warps required, a machine of the drum-drive type, running at around 330 metres/min., should be adequate.

Beaming efficiencies

Average beaming efficiencies with drum-drive equipment are around 36%. They are, of course, influenced by the quality of the yarn and hence the time required to attend to thread breaks. They also depend on the frequency of beam changes and creeling time. A beaming efficiency of 30.3%, in terms of machine-speed, has been assumed in the economic evaluations undertaken in chapter IV.

(b) Indirect warping

This system consists of winding the warp in separate width-way sections, each section being laid side-by-side on the horizontal barrel of a special beaming machine. When the required number of sections has been wound on to the barrel, all are unwound together as a single warp sheet either directly on to a loom beam or, more usually, on to a beam of somewhat similar dimensions to the loom beam. In this latter case, the sections are rewound on to the final loom beam in a beam-to-beam sizing operation. Reference to a form of section-warping, but using a slow-speed horizontal mill instead of a section beamer, has already been made in connection with warps prepared from hanks. However, the above indirect system is primarily suited to the preparation of continuous filament warps and will not therefore be referred to further in this paper.

I.3 Weavers’ warps, back beams, and beaming machine requirements

Weavers’ warps requirements for each of the fabrics being considered are set out in the upper section of Table II.1. The middle section of this table gives corresponding back beam requirements on the assumption that this method of warp preparation is used for all fabricks, including the denim cloth (T1). In the latter case, the method of dyeing on the back beam (mentioned earlier) might be used. Alternatively, the processes of dyeing and sizing from back beams might be carried out in tandem. The lower section of the table deals with beaming machine operating times and requirements. Each section gives figures for both medium-scale and large-scale production levels. In the cases of the back beam and beaming machine requirements, figures are given for single day-shift, two-shift, and three-shift working.

For small-scale productions, assuming that the direct beaming method is used, the times for making back beams will be approximately proportional to the lengths which must be produced (at an establishment supplying sized weavers’ warps on beam to a number of hand-loom weaving concerns).

The calculated machine requirements show that a beaming machine would be fully utilised on a single shift basis if total production is equal or exceed 2,000,000 meters per year. For example, for fabric P4, the yearly production must be 4,000,000 meters if a beaming machine were to be fully utilised on a one-shift basis.

Table II.1
Weavers’ warps, back beams and beaming machine requirements

WEAVERS’ WARPS REQUIREMENTS

Cloth ref.

Warp
yarn

Total warp threads in cloth 1 m wide (includes selvedges)

Warp length on loom beams-length includes 10% allow. for crimp and waste

Loom warp requirements per year in relation to production levels





Medium-scale (1.0M m/yr)

Large-scale (5.0M m/yr)

No.

Tex


Metres

No.

No.

P1

48

1,632

1,100

1,000

5,000

P2

24

2,652

1,650

667

3,334

P3

16

3,262

2,200

500

2,500

P4

12

3,776

2,750

400

2,000

T1

30

4,080

1,100

1,000

5,000

T2

30

2,040

1,980

556

2,778

T3

24

3,672

1,320

834

4,167

T4

30

2,856

1,540

715

3,572

WARPERS’ BACK BEAMS REQUIREMENTS

Cloth ref.

Ends per back bean and back beams per set to obtain total ends as in Col. 3 above

Warp length on each back beam

Number of loom beams obtained from 1 set of back beams

Back beam sets requirements per year in relation to production levels.





Medium-scale
(1.0M m/yr)

Large-scale
(5.0M m/yr)

No.

Number of ends

Number of back beams

metres

No.

No.

No.

P1

408

4

8,800

8

125

625

P2

442

6

16,500

10

67

334

P3

466

7

24,200

11

46

228

P4

472

8

33,000

12

34

167

T1

510

8

12,100

11

91

455

T2

510

4

11,880

6

93

463

T3

459

8

15,840

12

70

348

T4

476

6

13,860

9

80

397

BEAMING MACHINE PRODUCTION TIMES AND MACHINE REQUIREMENTS

Cloth ref.

Time to warp one set of back beams

Total annual machine times to meet, required production scales (hours)

Beaming machine requirements in relation to total annual working hours and to required production scales. (Nos. of m/c)

No.

hr.

Medium-scale
(1.0M m/yr)

Large-scale
(5.0M m/yr)

Day shift
(3000 hr)

Two-shifts
(5000 hr)

Three-shifts
(7000 hr)





Med.
1 M

Large
5 M

Med.
1 M

Large
5 M

Med.
1 M

Large
5 M

P1

5.87

734

3,669

0.25

1.23

0.15

0.74

0.11

0.53

P2

16.50

1,106

5,511

0.37

1.84

0.23

1.11

0.16

0.79

P3

28.24

1,299

6,439

0.44

2.15

0.26

1.29

0.19

0.92

P4

44.0

1,496

7,348

0.50

2.45

0.30

1.47

0.22

1.05

T1

16.13

1,468

7,340

0.49

2.45

0.30

1.47

0.21

1.05

T2

7.94

739

3,676

0.25

1.23

0.15

0.74

0.11

0.53

T3

21.20

1,484

7,378

0.50

2.46

0.30

1.48

0.22

1.06

T4

13.90

1,112

5,519

0.37

1.84

0.23

1.11

0.16

0.79

N.B. Assumed beam dimensions:-

Back beams - 28 in diam. flange; 8 in diam barrel; 54 in between flanges
Loom beams - 26 in diam. flange; 6 in diam. barrel; 42 in between flanges

Note: Beaming calculations used in Table II.1

The maximum warp length (cotton type yarns) which can be wound at medium pressure on to a flanged beam can be estimated from either of the following formulae:-

(a) Imperial units

(b) Metric units

in which:

D = Outer diameter of wound beam -

) Units = inches in (a), and cm



) in (b)


d = Barrel diameter of beam

)


--------------------------------------------------------------------------------------


Tex = yarn weight in grams per kilometre
Ne = number of hanks of 840 yards per lb weight

)


--------------------------------------------------------------------------------------

Ends on weavers’ beam = ends per back beam x back beams per set

I.4 Warp sizing

The subject of warp sizing is complex and is strictly outside the scope of this memorandum. However, the following should serve as some initial guidelines on this aspect of weaving.

For successful weaving of most cotton type fabrics, the warp threads require a protective coating of an adhesive film, referred to generally as a size paste. This coating enables the threads to withstand the abrasive action of weaving which largely take place during shedding (i.e. when the threads are drawn to-and-fro over or against the surfaces of parts such as heald eyes and reed dents, etc.) Without a coating of size, many threads - particularly of singles yarns - would quickly become seriously abraded and would break, thus making satisfactory weaving impossible.

(a) Size materials

Traditional size materials consist of an adhesive in the form of a natural or modified natural starch such as sago, maize, tapioca, farina, etc. The adhesive helps to bind the surface fibres together. It also helps to lay flat any projecting surface fibres or other protuberances which can cause obstructions during the crossing of the opposing warp sheets. However, adhesives of the kind mentioned above, if used alone, tend to increase the frictional forces as the threads rub against one another or against loom parts. To minimize these frictional forces, a natural fat, such as mutton tallow, is usually added to the size mixture. Alternatively, the lubricant may be applied separately as a surface coating to the thread (i.e. where it can have the most beneficial effect on friction). This latter matter is, however, more difficult to apply. The size is later removed from the woven cloth in the desizing and scouring processes which precede fabric bleaching, dyeing, printing and finishing operations. Ease of removal is therefore an additional requirement of a good sizing paste. The latter factor, in combination with an aim of helping improve the ease of size preparation and application, has led to the development of numerous proprietary size adhesives and lubricants. However, some of these, even when successful, can be costly. In the United Kingdom, sago starch was the most common adhesive in use for many years. Recently, proprietary adhesives, many of which are synthetic products, are being used to a large extent. Some gains in productivity may be achieved with adequate technical expertise, thus offsetting the increased cost of the adhesives. However, for developing countries, the use of the most readily available low-cost adhesive, having reasonable sizing properties, could well be the more important factor.

(b) Preparation of size paste

In preparing the size paste, the dry ingredients (if natural starches) are mixed with the lubricant in an appropriate known volume of water. The mix is then boiled in order to break down the starch granules to form a paste of reasonably stable viscosity, and which the dry yarns can readily take up in the sizing process. Different starches behave differently in these respects. For example, sago reaches a fairly stable viscosity after vigorous boiling for a period of about two hours while farina, which is very thick when first boiled, rapidly loses viscosity as boiling proceeds. Farina is, for this reason, more difficult to control. It is therefore important that great care is exercised in the preparation and application of size mixings. Otherwise, the warps can prove impossible to weave.

The graph in Fig. II.1, although hypothetical, typifies the relationship between the warp breakage rate (in weaving) and the percentage, by weight, of oven-dry ingredients in a sago and tallow size applied to a cotton warp. The points on the curve marked A and B indicate the approximate limits of the range of percentage size on yarn at which warp breaks are at a minimum. From the start of the curve at the left of the graph and up to point A, the breakage rate falls rapidly as the amount of size on yarn is increased. From point B and beyond to the right, the breakage rate starts to rise once more, largely as a consequence of protuberances along the threads becoming too stiff: these cause shedding obstructions between threads as the healds cross and re-open in shedding. The aim of good sizing is therefore to obtain a target amount of size on yarn somewhere within the range A - B. Unfortunately, there is no set formula which will guarantee an optimum sizing/weaving condition at a first attempt for any chosen size on any type of warp. Trial weaving experiments on short lengths of warp sized to provide a range of ‘Known’ percentage size conditions will probably constitute the best guide. However, Table II.2 provides empirical data which can be used to estimate the amounts of size on yarn required for best weaving when using sago as an adhesive and tallow as a lubricant on cotton (and also on spun viscose) warps of the kinds listed.


Figure II.1 Relationship between warp breakage rate and per cent size on warp

Table II.2
Estimated per cent size on yarn for good weaving

Yarn count

Warp particulars
Fibre

Warp ends
per cm.

Approximate % size on
yarn for good weaving

59 Tex

(10 Ne)

spun viscose

16

4

18.5 Tex

(32 Ne)

spun viscose

32

8 - 10

49 Tex

(12 Ne)

cotton

16

5

25 Tex

(24 Ne)

cotton

26

10

16.5 Tex

(36 Ne)

cotton

32

12

12 Tex

(50 Ne)

cotton

50

15

Note: The above percentages of size refer to weights of oven-dry solids on oven-dry yarn and apply to a sago/tallow mixture containing nominally 9% total dry solids, in a ratio of 10 parts sago to 1 part tallow, with 91% water after boiling the mix for a period of two hours to fully break down the starch and thus obtain a paste of stable viscosity. If other starches are used in place of sago, it will be necessary to vary the preparation in order to achieve a suitable viscosity paste. In this latter case, the target size percentage on yarn will generally be different from that indicated above. Precautions should be taken to ensure care and accuracy in the measurement of size ingredients and at all stages of preparation and application of the size paste.

(c) Sizing equipment

Equipment used for the sizing of warps of open-width sheet form, consists essentially of the following items:

- Weighing and measuring equipment for size ingredients.

- Size preparation equipment: becks or kettles in which the size is mixed with water and boiled as required.

- Creel for mounting the in-going warpers’ back-beam or full-warp beams for beam-to-beam sizing.

- Size application box (sow box) with yarn immersion rollers, and squeeze rollers to effect size penetration into the yarn and to remove surplus size.

- Means for drying the sized warp: steam-heated cylinders around which the warp passes are in common use, but hot-air or infra-red dryers may also be used.

- Split-rod system for separating warp threads which have become stuck together with size.

- Headstock with winding gear for winding up the sized warp on to a loom beam.

Apart from open-width warp-sizing, part warps may be sized in rope form. Single thread sizing may also be carried out with the aid of special equipment such as the Miniplus equipment referred to earlier. Rope sizing is commonly used in the preparation of multi-colour warps whereby each colour requires a separate dyeing and sizing operation. The separate ropes are later combined in the required thread-colour order and wound onto a loom beam (see section on dry taping).

(d) Warp sizing, machine productivity and requirement

The following calculations are based on a machine of 166 cm working width, equipped with 5 drying cylinders, and which has a total drying capacity of 350 kg per running hour:

- Nominal practical running speed: 50 metres/minute

- Mean running speed at 35% overall efficiency: 17.5 m./min.

- Machine output per hour: 17.5 x 60 = 1050 metres.

- Times to size annual warp requirements:



Table II.3 shows that full capacity utilisation of a sizing machine occurs only in the case of large-scale production when it is operated on a one-shift or two-shift basis. The production per machine could also be increased if machines with a higher drying capacity (e.g. one with seven or nine cylinders) were used. The problem of machine break-down and availability of spares must, however, be kept in mind since production would cease if the only machine available were stopped for any long period of time for repairs,

Table II.3
Sizing machine requirement in relation to total annual working hours and to annual sized warp requirement

Day shift only
(3,000 hr/yr)

Two shifts
(5,000 hr/yr)

Three shifts
(7,000 hr/yr)

Small
scale
0.035

Medium
scale
0.35

Large
scale
1.75

Medium
scale
0.21

Large
scale
1.05

Medium
scale
0.15

Large
scale
0.75

II. Production of pirns

When weft yarn is not on a package of suitable form to be placed directly onto the loom shuttle (i.e. when it is on ring rubes, cheeses, cones, or in hank form) it is necessary to rewind it on to pirn tubes of appropriate size.

Apart from overcoming the problem of initial package form, weft should be cleared, during winding, of any abnormally thick or thin places which could cause trouble during weaving or which might detract from the final appearance of the fabric. A simple mechanical yarn clearer should suffice for removing slubs in threads of non acceptable sizes.

Modern pirn-winders are generally complex precision machines which are outside the manufacturing capabilities of local semi-skilled labour in developing countries. No production diagrams are therefore included in this memorandum.

The maximum diameter and length of pirns suitable for any particular type of loom depends on the size of the shuttle and of shuttle lining. Most pirning machines incorporate means for adjusting the diameter and the length of the pirns which are wound as well as the spindle speed which controls the rate of winding. The ranges over which these settings can be altered is generally stated in the manufacturer’s technical handbook. Given the spindle speed, and knowing the diameter of the empty pirn-tube and that of the wound pirn, the effective mean package diameter and the yarn speed in winding can be calculated. On the basis of this information, it is possible to estimate the number of pirn-winding spindles required to meet a given weaving production target. The method and the spindle requirements for the eight fabrics (P1) - (P4) and (T1) - (T4) are set out below.

-

Assumed full-pirn diameter ‘A’

=

30 mm





-

Assumed empty pirn-tube diameter ‘B’

=

15 mm





-

Assumed machine spindle speed

=

10,000 rev/min





-

Yarn speed at 10,000 rev/min

=



=

45 x 3.142 x 5



=

707 metres/min





-

Yarn length wound per hour at 80% efficiency (metres)

=
=

707 x 60 x 0.8
33,936 metres





-

Annual weft-length requirement for cloth of 1 metre width (metres)

=

picks/metre + 10% (crimp and waste allowance) x annual cloth-length requirement





-

Annual pirning time requirement (hr)

=





-

Number of pirning spindle required

=

Tables II.4 and II.5 provide, respectively, the annual weft-length requirements in relation to scale of production and the numbers of pirning spindles required in relation to both production scale and annual working hours. Table II.5 shows that the maximum number of pirning spindles do not exceed 4 for small-scale units, 40 for medium-scale units, and 200 for large-scale units. The estimated number of pirning spindles do not take into consideration spindles out of action for any reason, including repairs.

Table II.4
Annual weft-length requirements in relation to scale of production (Units = Million, metres)

Cloth Ref No.

Small-scale prod.

Medium-scale prod.

Large-scale prod.

P1

176

1760

8800

P2

286

2860

14300

P3

352

3520

17600

P4

407

4070

20350

T1

264

2640

13200

T2

198

1980

9900

T3

264

2640

13200

T4

264

2640

13200

Table II.5
Numbers of pirning spindles required in relation to scale of production and to annual working hours

Cloth Ref No.

Annual working hours

Production level



Small scale

Medium scale

Large scale

P1

3000

2

18

87


5000

2

11

52


7000

1

8

38

P2

3000

3

29

141


5000

2

17

85


7000

2

13

61

P3

3000

4

35

173


5000

3

21

104


7000

2

15

75

P4

3000

4

40

200


5000

3

21

120


7000

2

18

86

T1

3000

3

26

130


5000

2

16

78


7000

2

12

56

T2

3000

2

20

98


5000

2

12

59


7000

1

9

42

T3

3000

3

26

130


5000

2

16

78


7000

2

12

56

T4

3000

3

26

130


5000

2

16

78


7000

2

12

56

TO PREVIOUS SECTION OF BOOK TO NEXT SECTION OF BOOK