Tricot Warp Knitting Machine | Working Process of Tricot Warp KnittingMachine

Experiment name: Study on yarn to fabric path diagram of Tricot warp knitting machine.

Introduction:
Warp knitting m/c is one kind of flat bed m/c. This m/c produces the knitted loops in wales direction. There are two major classes of warp knitting m/c. They are the ‘Tricot’ & the ‘Raschel’ warp knitting m/c. The ‘Tricot’ warp knitting m/c is also termed as automatic warp knitting of its function.

Objectives:
1. To know about the yarn to fabric path diagram of Tricot warp knitting machine.
2. To know about the name of the differents parts of the machine.

Main parts of the Machine:

1. Compound needle.
2. Needle bar
3. Guide bar
4. Sinker& sinker bar
5. Sliding latch
6. Sliding latch bar
7. Comb
8. Cloth roller.
9. Link
10. Rocker shaft
11. Pattern chain.
12. Pattern drum.
13. Main shaft.
14. Intermediate shaft.
15. Let-off mechanism
16. Take-up mechanism.
17. Machine A/C.
18. Toothed belt/ Timing belt.
19. Warp beam.
20. Bottom Beam.

M/C specification:

1. Brand: LIBA
2. Origin: W. Germany
3. Manufacturing Company: MASCHINEN FABRIK, NAILA.
4. Manufacturing Year: 1991 
5. Width: 84 inch/ 213 cm
6. Type: COP 2K
7. Gauge: 28 

M/C Description:
Compound needle is used in the m/c. With the help of the pattern drum and the chain link the patterning is done. The gears are merged in oil bath for smooth operation. There are two back beam for yarn supply. The yarns come through guide bar and through the needle the cloth is take down by cloth roller 

Tricot warp knitting machine

Function of different parts of M/C:
1. Compound needle: In Tricot warp knitting m/c compound needle is used. To form loop and produce the fabric is the main function of the needle.

2. Needle bar: A needle bar is used in this m/c. The main function of it is to hold the needles together and helps the needles to move unison while loop forming.

3. Guide bar: Guide bar is used in this m/c to guide the yarn properly to the needle. It feeds the yarn around the needle and controls the rate of warp feed from the warp beam by making lapping movement.

4. Sinker and Sinker bar: In the tricot warp knitting m/c tricot sinker is used to hold down the loops produced by the needles. The sinker bar keeps the sinkers together to move unison while knitting. The main function of the sinker is to hold down, knock over and supporting the fabric loops.

5. Sliding latch: In warp knitting m/c compound needles are used. A sliding latch is used here to close the hook while knitting.

6. Sliding latch bar: In warp knitting m/c the sliding latches remain unison. The latch bar keeps the latches together and helps it to move unison while knitting.

7. Cloth roller: The produced fabric is wound on the cloth roller.

8. Let-off mechanism: The process of releasing the warp yarns according to the requirement of the m/c and speed of cloth roller is the main function of let-off mechanism.

9. Take up mechanism: It helps the produced fabric to wound on the cloth roller

in proper tension. There are 3 take-up r/r in this m/c. It also gives proper tension to the warp sheet and controls the speed of warp beam.

11. Link: In the warp knitting m/c the link is used to make design in the knitted fabric. The different links used here has different thickness and thus it helps to produce design.

12. Pattern chain: The pattern chain is the chain of links joined with each other. The pattern chain helps the m/c to produce design.

13. Pattern drum: It is a drum, which gives motion to the pattern chain. There are groove on it and the pattern chain is placed on it. It gets motion from the m/c driving motor through gearing.

14. Comb: In this warp knitting m/c the comb is used to separate the warp yarns coming from the warp beam. It works as the reeds of the weaving m/c and also controls the fabric width.

15. Warp beam: In tricot warp knitting m/c warp beam is used to supply the warp yarns parallely. There are 8-warp beam in this m/c. 4 beam are on the upper side and 4 are to the downside. These beams are not so big as the weavers beam.

15. Machine A/C: The m/c a/c is one kind of cooling device, which keeps the m/c parts and the motor from over heating and damage while running continuously.

16. Main shaft: The main shaft of this m/c gives the m/c motion from the motor.

17. Lubrication: The m/c has automatic lubrication system.

18. Controlling unit: The controlling unit is used to control the m/c easily. It has a digital control unit.

19. Toothed belt: In this m/c the toothed belts are used to transfer motion without any slippage.

Conclusion:
By this experiment I learned about the Tricot warp knitting m/c and their several parts. I also learned the function of the different parts used here. This is a modern m/c and so this experience will help me in my future practical life.

Reasons for Why so Called Sulpher Dye | Popularity of Producing BlackShades with Sulpher Dyes | Comparison Between Sulpher Dyes & Vat Dyes

Reasons for why so called:

The dyes are so called as they contain Sulpher linkage within their molecules but dissolved in a solution of sulphide which acts as a reducing agent, breaking the Sulpher linkage and converting the molecules into simpler components which are soluble in water and substantive towards cellulose. 

Dye–S–S–Dye (Water insoluble Sulpher dye molecule)

Popularity of Producing Black Shades with Sulpher Dyes:

1. Low cost
2. Fair to good light fastness
3. High Wash fastness
4. Easy to apply
5. Low energy required
6. Chemical resistance is moderate to good.
7. Wide range of shades especially on heavy, durable shades on apparel fabric.

 Comparison between Sulpher & Vat Dyes:

 

Subject	Sulpher Dye	Vat Dye
1.   Molecular Size	1.      Dye molecules are very Large	1.   Smaller than Sulpher
2.   Shade	2.      Gives dull shade due to varying conditions	2.   Gives bright shades
3.   After reduction	3.      Smaller size molecules are obtained D–S–S–D+[H]  à D–SH + SH–D	3.   Vat dyes are reduced .
4.   Fabric Dyed	4.      Cotton, Rayon, Nylon & P/C	4.   Cellulose Rayon etc
5.   Hydrolysis	5.      Under high temperature and Humidity	5.   Susceptible to hydrolysis i.e. easy to Hydrolysis.
6.   Wash Fastness	6.      Good to very good	6.   Excellent
7.   Price	7.      Cheaper than Vat dye	7.   Very costly dye
8.   Light fastness	8.      Good to very good	8.   Excellent for anthraquinone.
10.             Sulpher linkage	9.      Contain Sulpher linkage	9.   No Sulpher linkage is present.
10.             Ionization	10. The dye molecules are negatively ionized after reduction	10.             Same

Dyeing of Cellulosic Fibres with Sulpher Dyes | Sulpher Dyeing Processof Natural Fibers

The sequence of dyeing with Sulpher dyes is as following:

Goods Preparation
↓
Dye Solution preparation
↓
Dyeing
↓
Oxidation
↓
After treatment
↓
Dyed Goods

Ø Typical Recipe:
The Typical recipe for dyeing is as below:-

1. Sulpher Dye  : 10% (On the weight of the fabric)
2. Na2S (Reducing Agent)  : 1.5%(on the weight of the Dye)
3. Salt  : 8 gm/litre(NaCl)
4. Soda Ash (NaCO3)  : 7 gm/litre
5. Temperature  : 1000C
6. Time  : 90 minutes
7. Material: Liquor  : 1:20

Sometimes a chelating agent EDTA is added to chelate any metal salt extracted from the cotton goods & effectively remove these ions from the dye bath. This is necessary to prevent a harsh texture forming on a textile.

Ø Good Preparation:
Only normal pretreated fabric (scoured, bleached) is required. Mercerized cotton goods causes an increased colour yield of 30-40%, But goods bleached by Na-Hypochlorite should not be dyed by Sulpher dyes:

Ø Dye solution preparation or Reducing Step:
Required amount of dye, soda ash & Na2S are taken in a beaker and a little amount of cold water is added to make a paste. In a separate vessel the rest of the water is boiled and the paste is added to it. Then the mixture is boiled for 5 minutes to make the dye completely reduced.

Ø Dyeing:
At first dye solution is taken in a dye bath & the fabric is immersed in that solution. Then it is heated for 10-15 minutes. Then half of the total NaCl solution is added and temperature is raised to boil & then the rest amount of NaCl is added. Dyeing at this temperature is continued for about 30 minutes. Then the steaming is turned off and the application continued in cooling liquor for a further half hour. This steaming helps to diffuse the dye in to the fabric before fixing. Retained dye liquor should be rinsed out immediately from the surface of the fabric.

Dyeing Curve

Ø Oxidation:
After dyeing the reduced water soluble form of the dye should be make insoluble by oxidation, to fix it on the fabric permanently. For this oxidation, we may use K2Cr2O7, CH3COOH. Na-perborate, Na2O2 etc. The typical recipe of oxidation is as below:

1. Na-Perborate à 0.5-1 gm/litre
2. Temperature à 40-500C
3. Time à 20 minutes.

Ø After Treatment:
1. The dyed substance is soaped which makes the colour bright and makes shade permanent.
2. The light fastness property of Sulpher dyes which is generally good can be improved by after treatment with certain metallic salts. Thus a treatment with CuSO4 & CH3COOH in presence of K2Cr2O7 improves the light fastness. When the dichromate is also present the washing fastness is slightly improved.

The following recipe is used for after treatment:

CuSO4 Solution à 1-2% (on the weight of goods)
CH3COOH (60%) à 1-2%
Temperature à 700C
Time à 20-30 Minutes
 

Precaution in the dyeing process: 

 
The precautions in the dyeing process with the Sulpher dyes are mentioned below:-
1. In the application of Sulpher dye, the dye bath should not contain Ca- Salts. If they are present in the form of insoluble co-compounds with the Sulpher dyes which precipitated easily in closed machines and form sludge when restrict the circulation of the dye liquor.
2. The dye should be dissolved with soda.
3. Great care should be taken during reduction process because over reduction should lower the affinity of dye towards the fibre. As a result dull shade will appear and a lot of dye stuff will go to waste.
4. Fabric must not to expose to air during dyeing to prevent precipitation & oxidation. This will cause uneven dyeing.
5. To prevent uneven dyeing in the fabric selvedge more amount of Na2S or NaOH and salt should be added in case of the jigger dyeing machine.
6. To prevent the broziness the dye liquor should not be very worm.
7. Goods dyed with Sulpher black should be after treated with a solution of K2Cr2O7 followed by rinsing. This will prevent Sulpher black tendering.
 

Control of Dyeing:
Reduced Sulpher dyes are similar to direct dyes. Because they can also be exhausted by adding common salts (NaCl) or Glauber’s salt (Na2SO4.10H2O) to the dye bath.

Sodium bi sulphite (NaHSO3) and ammonium sulphate {(NH4)2SO4} may also act as exhausting agents. Especially in dyeing combination shades. NaHSO3 is an acidic salt and (NH4)2SO4 is an acid liberating agent. They reduce the pH of dye bath and produce 15-20% deeper shades than common salt, when used as the exhausting agent. But the shades produced in presence of them are less bloomy and dull.

When NaHSO3 is used alone the rate of exhaustion is low but the produced shade is brighter and bloomier than common salt (NaCl) dyeing.

The use of the exhausting agents causes wastage of dye but as the Sulpher dyes are relatively cheap this wastage is not considered. Especially in case of medium & light shades. 


Improving of Fastness Properties:

The light fastness of the Sulpher dyes which is generally good can be improved by after treatment with certain metallic salts. Thus a treatment with CuSO4 & CH3COOH in presence of K2Cr2O7 or Na2Cr2O7 improves the light fastness. When the dichromate is also present the washing fastness is slightly improved. In actual practice the following after treatments are given: -

1. CuSO4 Solution à 1-2% (on the weight of goods)
2. CH3COOH (60%) à 1-2%
3. Temperature à 700C
4. Time à 20-30 Minutes

The latter one also improves the washing fastness of Sulpher dyed textile materials.