CHAPTER 6
RAW SILK REELING 

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6.1   Introduction

Silk reeling is the process by which a number of cocoon baves are reeled together to produce a single thread. This is achieved by unwinding filaments collectively from a group of cooked cocoons at one end in a warm water bath and winding the resultant thread onto a fast moving reel. Raw silk reeling may be classified by direct reeling method on a standard sized reel, indirect method of reeling on small reels, and the transfer of reeled silk from small reels onto standard sized reels on a re-reeling machine. The last technique is primarily applied in modern silk reeling processes.

6.2   Various silk reeling devices

There are many types of silk reeling machines in use. The major structural features of the Sitting Type Reeling Machine, the Multi-ends Reeling Machine and the Automatic Reeling Machine are shown in Table 20.

1.     Hand spinning wheel

This primitive spinning apparatus is operated by two hands – one to drive the wheel and the other to feed in cocoons. One end of the reeling thread is wound onto each wheel, while cocoons are boiled in a separate pot.

2.     Charka type reeling machine

The Charka type is in use in India. This machine is operated with separate work motions in reel driving and cocoon feeding to reeling ends by two men per machine. Each machine has 3 ends or more to a reel, which is the same size as the large wheel of the Re-reeling machine in order to save the re-reeling process (direct reeling method).

3.     Sitting type reeling machine

There are two kinds of sitting type reeling machines, foot operated and motor-driven (see Appendix, Figure 17). The motor-driven reeling machine is not equipped with the stop motion attachment (see appendix, Figure 18). There are obstacles to the production of good quality raw silk as the raw silk thread is wound too rapidly to maintain good quality control.

Table 20. Comparisons of structural features of various reeling machines

Kinds of machine

Sitting type reeling (m/c)

Multi-ends reeling (m/c)

Automatic reeling (m/c)

No. of reeling ends per basin

4 (2 to 8)

20 (10 to 40)

20

End-groping apparatus

Hand-driven

Semi-automatic

Automatic

End-picking apparatus

Hand-driven

Hand-driven

Automatic

Cocoon supplying apparatus

None

None

Equipped

End-feeding apparatus

None

Equipped (hand feeding)

Equipped (machine feeding)

Stop motion

None

Equipped

Equipped

Traverse guider

Equipped

Equipped

Equipped

Temperature of reeling bath

65-80 C

30-45 C

30-45 C

Reeling velocity (meter per minute)

180-250

50-80

120-200



4.     Multi-ends reeling machine

This machine eliminates the disadvantages of the Sitting type reeling machine by increasing the number of reeling thread ends per basin and reducing the reeling speed. The operator must stand when running this machine as the number of reeling threads per basin increases by twenty-fold. This is also called a "Standing type reeling machine". Reeling efficiency is unchanged. Quality is better due to reduced speed.

The Multi-ends reeling machine is composed of driving part, groping ends, picking ends, standby bath, reeling part, jetboute, stop motion, traverse guider, small reels, steam heating pipes and clutches (see Appendix, Figure 19).

The cooked cocoons contained in the tubs are carried into the groping ends portion of the reeling machine. From there, cocoons are moved into the picking ends apparatus. After correctly processing, the cocoons go to the standby bath for cocoon feeding. They are picked up by the reeler and fed to the reeling thread. During this step a number of cocoons will be dropped thus reducing the ratio of reeling cocoons per thread. The normal speed of cocoon feeding by a skilled reeler is around 16 times per minute. The reeling thread passes through the jetboute, silk button, first guider, second guider, third guider, fourth guider, traverse guider, in that order and then is wound onto the small reels.

The cocoons dropped during the reeling process are gathered and reprocessed starting from the groping end section. The croissure of reeling thread is made between second guider and third guider, and the length of croissure is not for twisting of thread but for cohesion of thread by rubbing of composed filament. Typically, one set of Multi-ends reeling machines consists of ten basins with each basin having twenty ends or reels.

Basin: The basin is rectangular with well-rounded corners and edges. It is only 10 to 12 cm deep. It is commonly made of dark coloured porcelain. The basin is subdivided into sections, each intended for a specific job such as brushing, end gathering of baves, stocks in reserve and waste collection.

Reels: The reels of the Multi-ends reeling machine have a circumference of 75 cm. The frame of the reel is made of light metal or plastic. The reels are fitted into reel carriers and driven by a transmission shaft by connecting gears.

Traverse guider: To ensure narrow and long web on the hank of the reel, a cam type traverse assembly has been fixed. This will make a convex surface in the hank, which is wound on the reel. The centre part of the hank is higher than the two axis.

Thread button: Porcelain button thread-guiders are used for removing any dirt adhering to the thread passing through the tiny aperture in the button.

5.     Automatic reeling machine

In raw silk production, the continuing increase of labour costs has mandated automation. Around 1950, the Automatic reeling machine, which controls the number of reeling cocoons per thread, was invented. Shortly thereafter, it was replaced by a second Automatic reeling machine, which could automatically control the size of the reeling thread.

The Automatic reeling machine mechanizes the processes of groping ends, picking ends; cocoon feeding to reeling thread and separation of dropped end cocoons during the reeling process. The efficiency of the Automatic reeling machine compares favourable with the manual Mult-ends reeling machine.

The Automatic reeling machine though built to replace manual reeling, still requires manpower for problems with the reeling thread, which must be corrected by hand. A moderate amount of cooked cocoons are carried to the newly cooked cocoon feeder (3) and then removed into the groping end part (4)

The end groped cocoons go to the picking end part (5) and the correctly picked end cocoons are dispensed to the cocoon supplying basket (8) which continuously rotates around the reeling basin on an endless chain belt. Usually, the reeling method is classified into the fixed cocoon feeding system and moving cocoon-feeding system.

In the case of the fixed cocoon feeding system, the correctly picked end cocoons in the rotating cocoon baskets are poured into the arranging basin (11) and here the picked end of each cocoon is hung on the end holding reel (7). When the size detector of the reeling thread indicates the feeding of cocoons, the picked end cocoons on standby are fed to the reeling thread by a feeding spoon. The reeling thread fed by picked end cocoons passes through the jetboute (23), silk button, first guider, second guider, third guider, fourth guider, denier indicator (5’), fifth guider and traverser (3’), and then it is finally wound onto small reels (1’). The end dropped cocoons are placed into the cocoon flowing tunnel by the remover plate. They are carried into the pupa separating drum (14). However, more reelable cocoons are poured into the end groping part (4) by the conveyor belt (15) and reels-finished cocoons are placed into the dropped-pupa case (17) for parchment layer cocoons (Figures 13 and 14).

In the case of the moving cocoon feeding systems, the correctly picked end cocoons are contained in the moving cocoon basket equipped with cocoon feeding apparatus. They are fed by the feeding fork of the cocoon basket, which move simultaneously around the reeling basin. The denier indicator of the reeling thread indicates the feeding motion of the cocoon. After cocoon feeding, the reeling path of the moving cocoon feeding system is the same as that of the fixed cocoon feeding system.

Generally, one set of the Automatic reeling machines has 400 ends, while one basin has 20 ends. The operating efficiency of the Automatic reeling machine is easily affected by cocoon qualities, drying and cooking machinery and quality of reeling water.

Ground plan of automatic reeling machine

Figure 13. Ground plan of automatic reeling machine

  • Motor,
  • Small reel speeding changing device,
  • New cocoon feeding device,
  • Brushing device,
  • Automatic end picking device,
  • Picked cocoon replenisher,
  • End holding reel,
  • Cocoon supplying basket,
  • Water supplying tank for basket,
  • Traverse gear,
  • Arranging basin,
  • Reeling basin,
  • Conveying gutter,
  • Pupa separating device,
  • Conveyor belt case,
  • Roof cover,
  • Dropped-pupa case.

    Side view of automatic reeling section 1. Small reel, 2. Rotating device, 3. Traverser, 4. Stop motion, 5. Denier indicator, 6. Jetboute, 7. Shatter for reeling cocoons, 8. Reeling basin, 9. Arranging basin, 10. Cocoon supplying basket, 11. Conveyor gutter, 12. Rotating device for jetboute.

    Figure 14. Side view of automatic reeling section
    1’. Small reel, 2’. Rotating device, 3’. Traverser, 4’. Stop motion, 5’. Denier indicator, 6’. Jetboute, 7’. Shatter for reeling cocoons, 8’. Reeling basin, 9’. Arranging basin, 10’. Cocoon supplying basket, 11’. Conveyor gutter, 12’. Rotating device for jetboute.

     

    Size detector (gauge type) 1. Gauge glass, 2. Grooved gauge glass, 3. Gauge plate, 4. Washer, 5. Binding bolt, 6. Special nut, 7. Indicating ring, 8. Detection limiting rod, 9. Adjusting weight

    Figure 15. Size detector (gauge type)
    1. Gauge glass, 2. Grooved gauge glass, 3. Gauge plate, 4. Washer, 5. Binding bolt, 6. Special nut, 7. Indicating ring, 8. Detection limiting rod, 9. Adjusting weight


    1.     Brushing and picking section
  • An automatic ten-brush unit brushes cocoons with independent arms rotating in reverse motion on an axis in circular basins.

    Picking frames rotating in one direction pick off the brushed cocoon filaments when a cam during the operation raises the brushes. Selective picking is completed in the most effective manner by this equipment. To maintain the exact number of cocoons at each reeling end, a control device is attached which detects the amount of cocoons in the cocoon suppliers and automatically supplements deficiencies in the number of cocoons.

    2.     Reeling section

    The denier indicating and detecting device.

    In these devices, the yarn constantly passes through the denier indicator and detector, which are set to a given size. The size of thread being reeled is detected through the balance between the friction of the running thread and an eccentric weight fitted on the denier indicator.

    When the thread becomes thinner than the fixed limit, the denier indicator indicates the necessity of feeding-ends. This indicator is composed of two gauge glass plates with other pieces of gauge plate which have a slit between them corresponding to the given size of thread to be reeled. The size of yarn may be adjusted to the required sizes by varying the irregular weight with the denier-adjusting device; if a wider range of adjustment is required the denier indicators have to be replaced.

    Conveyor system for cocoon suppliers

    The fixed end feeding system is employed together with a conveyor system to carry cocoon supplies and feed cocoons to the reeling section whenever required.

    End feeding for cocoons suppliers

    Cocoons are supplied to the conveyor, which rotates constantly around the reeling section. The feeding lever fixed to the detecting mechanism will trigger the driving lever on the cocoon supplier only when the size of yarn becomes thinner than the required denier during reeling operation.

    Stop motion

    If there is a defect in the reeling, the reel is automatically stopped by a brake, which is activated by contact pressure from operation of the detector level.

    Dropped cocoon gatherers

    The apparatus gathers baskets that have collected all cocoons dropped during end feeding. These are carried to the dropped cocoon separator. These baskets travel intermittently between the cocoon suppliers.

    Separator of dropped cocoons

    The device accurately distinguishes and separates pupae, dropped middle layer cocoons and thick layer dropped cocoons.

    6.     Semi-automatic reeling machine

    This is a mixed-mode or hybrid machine between the automatic and multi-ends reeling machines. As an application, this type is better for improved reeling efficiency and raw silk quality than the multi-ends reeling machine. The semi automatic reeling machine can be operated with poor quality cocoons, but relies on more labour than the automatic reeling machine.

    The cooked cocoons are carried into the groping end part (10) and the end-groped cocoons are removed to the picking end part (11). The correctly picked end cocoons go through the cocoon supplying basket (9) and then to the arranging basin (8). When the size detector of the reeling thread indicates the feeding motion, the picked end cocoons on standby are fed to the reeling thread by a feeding spoon. The reeling thread passes through the jetboute, silk button, first guider, second guider, third guider, fourth guider, size detector, fifth guider and traverse guide, and then it is finally wound onto small reels (4) (Figure 16).

    The end dropped cocoons are collected by the cocoon buckets (13) and removed to the cropped cocoon basin, where more reelable cocoons are separated and then poured into the groping end part (10). The principal difference between a semi-automatic reeling machine and an automatic reeling machine is that the cocoon end groping, cocoon end picking and cocoon carrying are manual.

    6.3 Methods of silk reeling

    a)    Reeling velocity (R.V.)

    Reeling velocity is defined as the winding speed of raw silk on the reel. The reeling velocity is measured as the length of raw silk reeled during 1 minute or as the revolution number of the reel per minute. It is usually calculated by the following formulas.

    Where formula (1) applies to the automatic type, formula (2) applies to the multi-ends type.

    Number of end feeding :      Automatic type -       1.2-1.5 pc/min./reel
                                               Multi-ends type -      12-14 pc/min./man

    None breaking reelable bave =   length of cocoon filament (m)
                                                      x cocoon reelability (percent) 

    Dimension and structure of semi-automatic reeling machine 1. Motor, 2. Traverser gear, 3. Chain stepless regulator, 4. Small reel, 5. Stop motion device, 6. Denier control device, 7 Brush, 8. Arranging basin, 9. Cocoon carrier, 10. Brush, 11. Picking bath, 12. Brush drive device, 13. Reconveying bucket (dropped cocoon), 14. Steam pipe.

    Figure 16. Dimension and structure of semi-automatic reeling machine
    1. Motor, 2. Traverser gear, 3. Chain stepless regulator, 4. Small reel, 5. Stop motion device, 6. Denier control device, 7 Brush, 8. Arranging basin, 9. Cocoon carrier, 10. Brush, 11. Picking bath, 12. Brush drive device, 13. Reconveying bucket (dropped cocoon), 14. Steam pipe.

    The velocity of cocoon reeling affects the raw silk yield, reeling efficiency and raw silk quality (see Table 21 and 22). Optimum reeling velocity should be maintained for the best possible product.

    b)     Groping ends

    The high water temperature of the groping ends section dissolves sericin to a great extent and improves the reelability of the cocoon. However, it is apt to reduce raw silk percentage of the cocoon. Alternatively, too low water temperature in this process can reduce the groping end efficiency, the reelability percentage and the reeling efficiency.

      Table 21. Effect of various reeling velocities on silk yield and quality with different grades of reelability cocoon (Choe, et al. 1971)

      Cocoon reelability

      Reeling velocity (m/min.)

      Raw silk percent of cocoon

      Percentage of cocoon reelability

      Raw silk quality

      Neatness (%)

      Cleanness (%)

      Good Group

       

      Fair Group

       

      Poor Group

      90

      120

      150

      90

      120

      150

      90

      120

      150

      16.87

      16.80

      16.73

      16.36

      16.32

      16.21

      16.17

      16.07

      15.70

      72

      71

      71

      58

      57

      55

      50

      49

      46

      96.2

      95.2

      93.4

      91.9

      90.9

      90.5

      91.0

      89.5

      89.0

      96.8

      96.8

      94.5

      93.7

      93.8

      93.0

      92.3

      90.8

      90.6


       

      Table 22. Relationship between reeling velocity and evenness of raw silk quality (S. Kimura, et al. 1964)

      Reeling velocity (m/min.)

      Average evenness (%)

      Low evenness (5)

      50

      80

      110

      140

      170

      93.5

      98.0

      88.5

      87.3

      85.5

      86.0

      82.0

      80.2

      80.0

      78.4


    An appropriate temperature range is from 75 C to 80 C, but it will vary. The number of groping end cocoons is about 70-90, but this also varies with the cocoon quality. The pH value of water at this point should be from 6.8 to 7.0. the water should be changed often to prevent discolouration of raw silk.

    c)     Picking ends

    This is a very important function of the reeling operation, which can affect raw silk percentage and reelability. Correct end cocoons should not be permitted in picking ends to minimize cocoon filament waste.

    Insufficient picking ends causes the feeding of incorrect end cocoons, breaking down of the reeling thread, and affects the accuracy of the feeding end work.

    On the other hand, excessive picking ends reduce raw silk by causing an increase in waste. The picking end with too many cocoons can cause the work to be carried out inaccurately and is apt to increase waste of cocoon filament by repeated work on correct end cocoons. The number of cocoons for a picking end section should be below 40 pcs, and the recommended temperature of the water bath is 40 to 50 C. In automatic end-picking machines, the degree of end picking varies between 80 to 85 percent for good cocoons, 75 to 80 percent for medium ones and 70 to 75 percent for inferior ones.

    d)     Reeling bath

    6.4 Quality control during raw silk reeling

    The purpose of reeling process is not only to raise the raw silk yield of cocoons and reeling efficiency, but also to improve raw silk quality.

    1. Size development and evenness - To maintain reeling thread in the required size, the average cocoon number per thread must be adjusted by a check to produce silk thread in the same size throughout all ends during reeling. If the size is different from the required size it should be readjusted by the group size controller. This will reduce size deviation. By improving the accuracy of cocoon supplying each silk thread becomes uniform in size and different skein sizes are reduced. It can also improve the size deviation and evenness of raw silk quality through accuracy of cocoon supplying work and the improvement of cocoon reelability.
    2. Defects – Defects in raw silk are divided into super major defects, major defects and neatness defects. Defects occur based on reeling conditions. Types of defects and remedies are explained in Table 23.
    3. Cohesion – Good cohesion raw silk is needed for the warp of silk fabric. Factors that improve the cohesion are temperature, amount of reeling tension, sufficient croissure and good drying of raw silk.
    4. Colour – The water consistency and temperature of groping end part and reeling part affect the colour of raw silk. Therefore, the temperature control and water supply in the reeling machine should be constantly monitored to obtain a uniform colour of raw silk.

    Table 23. Prevention method against various types of cleanness defects

    Types of defects

    Prevention methods

    Waste

    1. Control of over or uneven cooking.
    2. Prevention of carry over cocoons by remaining in basins during reeling process.
    3. Reducing the number of standby cocoons in the reeling basin.
    4. Preventing the over swelling of cooked cocoons in the reeling process by controlling the temperature of grope end and picking end bath as well as maintaining a constant temperatur
     

    Large slug

    1. To 4) are same as above.
    2. Avoid low temperature cocoon drying
    3. Controlling the excessive increase of reeling speed and reeling thread
    Bad casts
    1. Keep the extra end of cocoon filament short when the correct end picked cocoons are fed to the reeling thread.
    Long knots
    1. When the broken thread are tied and knotted during the reeling or re-reeling process, the end of the tied and knotted thread must be cut off, leaving only 2 mm.
     

    Cork screws

    1. When the reeler has to eliminate a reeled out or bad cocoon during reeling, he should not use force to pull it out but should snip it out with his fingers as quickly as possible.
    Split ends
    1. Reduce friction effect on silk thread. Pulleys with cracks and splits on the surface should be removed. All pulleys should be perfectly polished to reduce split ends in the reeled yarn.
    Long loops
    1. Prevention of over or uneven cooking.

     

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