Manufacturing Process of Viscose Rayon

Viscose Rayon

It is a regenerated cellulosic fibre and cellulose is the raw material for producing this man made fibre.

The raw material is obtained from a special variety of wood called spruce.

Manufacturing Process

a. Purification of Cellulose:

The manufacture of viscose rayon starts with the purification of cellulose. Spruce trees are cut into timber. Their barks are removed and cut into pieces measuring 7/8" x 1/2" x 1/4". These pieces are treated with a solution of calcium bisulphite and cooked with steam under pressure for about 14 hours.
The cellulosic component of the wood is unaffected by this treatment, but the cementing material called lignin, which is present in the wood, is converted into its sulphonated compound which is soluble in water. This can be washed off, thereby purifying the remaining cellulose. This cellulose is treated with excess of water. After this it is treated with a bleaching agent (sod hypochlorite) and finally converted into paper boards or sheets. This is called wood pulp, which is normally purchased by the manufacturers of viscose rayon.

b. Conditioning of Wood Pulp:
The pulp sheets are cut by a guillotine to the required dimension and are kept in a special room. Air moves freely among the divisors by means of ventilatorys, the temperature is maintained at 30 deg celcius. In this way the desired moisture content can be had.

c. Steeping Process:
The conditioned wood pulp sheets are treated with caustic soda solution ( about 17.5%). It is called mercerising or steeping. The high DP cellulose (1000) is converted into soda cellulose. The sheets are allowed to soak (steep0 until they become dark brown in colour. This takes about 1-14 hours. The caustic soda solution is drained off and sheets are pressed to squeeze out excess caustic soda solution. 100 kg of sulphite pulp gives about 310 kg of soda cellulose.

4. Shredding or cutting process:
The wet, soft sheets of soda cellulose are passed through a shredding machine which cuts them into small bits. In 2-3 hours the sheets are broken into fine crumbs.

5. Ageing Process:
To obtain almost ideal solution of cellulose, the soda cellulose is stored in small galvanised drums for about 48 hours at 28 deg C. This process is called ageing process.The ageing process is essential. During This process, the DP od soda cellulose is decreased from 1000 to about 300 by oxygen present in the air, contained in the drum.

6. Churning Process or Xanthation:
After ageing, the crumbs of soda cellulose are transferred to rotating, air tight, hexagonal churners or mixers. Carbon disulphide ( 10% of the weight of the crumbs) is added to the mixer and churned together for 3 hours by rotating the mixers at a slow speed of 2 rev per minutes. Sodium cellulose xanthate is formed during this process and the colors of the product changes from white to reddish orange.

7. Mixing or dissolving Process:
The orange product i.e. sod.cell.xanthate is in the form of small balls. These fall into a mixer called dissover which is provided with a stirrer. A dilute solution of caustic soda is added, and the contents are stirred for 4-5 hours and at the same time, the dissovler is cooled. The sod.cell.xan. dissovles to give a clear brown thick liquor, similar to honey. This is called 'viscose' and it contains about 6.5% caustic soda and 7.5% cellulose.

8. Ripening Process:
This viscose solution requires to be ripened to give a solution having best spinning qualities. Ripening is carried by storing the viscose solution for 4-5 days at 10 to 18 deg. The viscosity of the solution first decreases and then rises to its original value. The ripened solutoin is filtered carefully and is now ready for spinning to produce viscose rayon filaments.

9. Spinning Process:

The viscose solution is forced through a spinnerette, having many fine holes ( 0.05-0.1mm) diameter. The spinnerette is submerged into a solution containing the following chemicals.
10% --> sulphuric acid, 18%- Sod sulphate, 1% - Zinc sulphate, 2% glucose, 69% water.

The spinning solution is kept at 40-45 deg celcius.

Sodium sulphate precipitates the dissoved sod. cell.xanthate. Sulphuric Acid converts xanthate into cellulose, carbon disulphide and sod. sulphate. the glucose is supposed to give softness and pliability to the filaments whereas zinc sulphate gives added strength.

The quality of viscose rayon filament formed depends upon:

1. The temperature of the spinning bath
2. The composition of the spinning bath.
3. The speed of coagulation
4. The period of immersion of the filament in the spinning bath.
5. The speed of spinning.
6. The stretch imparted to the filaments.

As a number of filaments emerge from the spinnerette, they are taken together to an eye at the surface of the spinning bath and then guided to two rollers from where they are wound on to a spindle.

Blending at draw frame

Blending at Draw Frame

This method is normally used for binary blends only. The required blend proportion is adjusted by the number of slivers of each component and the hank of respective slivers.

The fleece blending is done on the blending Drawframes specifically designed for this purpose. They are fed with 16-20 slivers at the back and therefore provide a much greater flexibility as regards the blend ratios.

Advantage

- Easier to obtain uniform blend ratio.
- During opening and carding, optimum settings fro each blend component can be used for better quality of output with less damage to the fibres. 

- Easy working.

Disadvantages

- Difficult to attain random arrangement of fibres in the yarn cross section.
- Additional drawing capacity needed.
- Separate opening lines needed for each component.

Blending of Combed Cotton Sliver and Polyester

Many Indian mills resort to this practice when the humidity control or conditions of machines is very poor.

Advantages
- Produces very intimate blend
- Trouble free running and high productivity at card.
- Less yarn imperfections due to better fibre individualisation because of reprocessing of the cotton component.
- Reduced number of d/f passages.
- Lower end breaks due to fewer slubs.
-better uniformity of dyeing due to more intimate blend.

Disadvantage
- Poor tenacity and evenness in blend yarn.
- High cotton nep content in blend due to reprocessing
- Need of additional b/r and card capacity
- Slightly higher waste in b/r and carding.

Optimum Blending Method of various Blends

1. For blends like P/V , blowroom blending is effective as they need similar b/r sequence.
2. For blending of manmade stack blending method is generally used.
3. The polyester /cotton or acrylic/cotton are generally blended at d/f because cotton component needs a severe opening and cleaning action
4. Where there is a problem of running 100% polyester on card, stack blending of polyester stock and combed cotton may be resorted to.
5. In case of v/c blend, they should be blended at the draw/frame as they need quite a different opening sequence.  

Terry Towel Manufacturing Process

In addition to what I have mentioned earlier, Terry Towelling is excellently described in this blog.
Replete with pictures, this post replies succintly the various process steps in manufacturing terry towel.

Jute Manufacturing Process

Please see the following link for jute manufacturing process

BI-STRETCH DENIM MANUFACTURING

I have received a query from one of my blog readers who wants to know more about bi-stretch denim manufacturing. I feel there are some specific issues that need to be delt with while dealing with bi-stretch fabric at the manufacturing stage:

1. How to control yarns at the ball warping, rope dyeing and the rebeaming stage.
2. Changes in looms to be done to handle stretch warp and stretch weft. It includes issues such as width control and others.
3. Sanforisation and skew control at the finishing stage.

If someone can contribute to this blog regarding these questions, she/he is most welcome.

Denim Manufacturing Process- the presentation

Please refer to the following presentation for the denim manufacturing process

Manufacturing Process of Terry Towel

Please see this link for Manufacturing Process of Terry Towel.

fashion manufacturing, a product development approach

Please see the link here

Systems of Cutting

Systems of Cutting in Garment Manufacturing

Cutting is one of the most important operations in garment manufacturing because it converts a fabric lay into garment components. Once the fabric has been inspected, relaxed if required, and spread according to the marker, the cutting operation separates the lay into parts such as fronts, backs, sleeves, collars, waistbands, linings, facings and other components.

The quality of cutting has a direct effect on garment fit, size consistency, seam matching, fabric utilisation and final appearance. Even if the sewing operation is carefully done, a poorly cut component can create defects that are difficult or impossible to correct later. Cutting should therefore be treated as a control point, not merely as a mechanical operation.

Table of Contents

1. Meaning and Importance of Cutting
2. Hand Shears
3. Straight Knife Cutting Machine
4. Round Knife Cutting Machine
5. Band Knife Cutting Machine
6. Computer-Controlled Cutting
7. Comparison of Cutting Systems
8. Factors Affecting Selection
9. Cutting Quality Requirements
10. Related Reading
11. References

1. Meaning and Importance of Cutting

Fabric cutting means separating the fabric lay into accurately shaped garment parts according to the marker. The marker is the cutting plan that shows the arrangement of pattern pieces on the fabric width. A good marker aims to maintain correct grain direction, reduce wastage and ensure that all garment components are available in the required sizes and quantities.

In simple terms, the cutting room links fabric planning with sewing production. If the fabric is spread correctly and cut accurately, sewing becomes smoother and garment measurements remain closer to specification. If cutting is inaccurate, the sewing department may face problems such as unequal panels, mismatched seams, distorted shapes and size variation.

Visual 1: Cutting room workflow showing fabric roll, spreading, marker placement and cut garment components.

2. Hand Shears

Hand shears are the simplest tools used for cutting fabric. They are normally used for single-ply or very low-ply cutting, especially in tailoring, boutiques, sampling, alteration work and made-to-measure garments. Since the tool is manually controlled, the operator can follow small details, curves and delicate areas with flexibility.

The main advantage of hand shears is low investment. No power supply, machine table or special maintenance is required. They are also useful when the production quantity is small or when the fabric is too delicate to be handled in a thick lay.

However, hand cutting is slow and highly dependent on the skill of the cutter. The accuracy may vary from piece to piece, especially when several garments are required in the same size. For this reason, hand shears are suitable for sample rooms and small-scale tailoring, but not for high-volume industrial production.

3. Straight Knife Cutting Machine

The straight knife cutting machine is one of the most commonly used machines in garment cutting rooms. It has a vertical blade that moves up and down while the operator guides the machine along the marker line. The base plate of the machine moves under the fabric lay, while the blade cuts through the plies.

A straight knife machine is popular because it is versatile. It can cut large panels, medium curves and many general garment components. It is suitable for medium to high lays, depending on the fabric type, blade size and machine capacity.

The machine combines mechanical cutting with manual guidance. The motor drives the knife, but the operator controls the direction and speed. Therefore, the final accuracy still depends on the operator’s skill, blade condition, lay height, fabric stability and careful handling of curves and corners.

Straight knife cutting is widely used because it gives a good balance of cost, speed and flexibility. It is especially useful in regular garment production where many different shapes have to be cut from the same lay.

4. Round Knife Cutting Machine

A round knife cutting machine uses a circular rotating blade. The blade rotates continuously and cuts the fabric as the machine is moved along the cutting line. It is useful for straight lines, gentle curves, trimming operations and section cutting.

The main advantage of a round knife is speed. It can cut long straight lines quickly and is useful when the garment components have simple shapes. It is also convenient for separating sections of the lay before more accurate cutting is done by another method.

The limitation of a round knife is its reduced ability to cut sharp curves and intricate shapes. Since the blade is circular, it does not easily negotiate tight turns such as necklines, armholes, small notches or complex pattern edges. It is therefore not the best choice for highly shaped components.

 Visual 2: Side-by-side schematic comparing straight knife, round knife, band knife and computer-controlled cutting.

5. Band Knife Cutting Machine

A band knife machine uses a continuous narrow steel blade running in a loop. Unlike a straight knife or round knife, the blade remains fixed in position and the operator moves the fabric section against the blade. This gives the operator better control for accurate shaping.

The band knife is suitable for precision cutting, trimming and re-cutting operations. It is often used when cut edges must be neat and accurate, especially for shaped components. It may be used after rough cutting when final accuracy is required.

The main advantage of the band knife is accuracy. Since the blade is narrow and fixed, it can produce smooth curves and clean edges. However, the machine is not portable, and the fabric pieces have to be brought to the table. The operator must also be skilled because the fabric has to be guided carefully while keeping the shape stable.

6. Computer-Controlled Cutting

Computer-controlled cutting is an advanced system in which the cutting path is controlled by digital marker data. The marker is prepared using a CAD system and the cutting machine follows the programmed pattern outlines automatically.

Modern automated cutting systems may use a reciprocating knife, laser, water jet or other specialised cutting heads depending on the material and end use. In apparel manufacturing, automated knife cutting is commonly used for fabric lays because it gives good accuracy without excessive heat damage.

The main benefit of computer-controlled cutting is repeatability. Once the marker and cutting parameters are correctly set, the same shape can be cut consistently across multiple lays and batches. This reduces dependence on manual cutter skill and improves control over cutting accuracy.

The main limitation is cost. Computerised systems require high investment, trained operators, maintenance support, CAD/CAM integration and sufficient production volume. For small tailoring units, hand shears or simple cutting machines may be more economical. For large factories, automated cutting can improve speed, fabric utilisation and planning efficiency.

7. Comparison of Cutting Systems

Cutting system	Best suited for	Main advantage	Main limitation
Hand shears	Tailoring, samples, alterations and made-to-measure garments	Low cost and high flexibility	Slow and dependent on cutter skill
Straight knife	General bulk garment cutting	Versatile and suitable for many garment parts	Accuracy depends on operator control
Round knife	Straight cuts, broad curves, trimming and section cutting	Fast for simple cutting lines	Not suitable for tight curves and complex shapes
Band knife	Accurate shaping, trimming and re-cutting	Clean and precise cut edges	Fixed machine and skilled handling required
Computer-controlled cutting	Large-scale industrial production	Fast, accurate and repeatable	High investment and technical support required

8. Factors Affecting Selection of Cutting System

The selection of a cutting system depends on the nature of production. A tailor making one garment does not need the same equipment as a factory producing thousands of pieces. The number of garments, lay height, marker complexity and delivery schedule all influence the decision.

Fabric behaviour is also important. Slippery fabrics, stretch fabrics, loosely woven fabrics, checks, stripes, thick fabrics and delicate materials may require different handling methods. A fabric that shifts easily during spreading or cutting may need a lower lay height and more careful control.

The relationship between lay height and accuracy is important. If \( n \) represents the number of plies in a lay, then one cutting action can produce \( n \) identical components, provided the lay remains stable and the blade cuts accurately through all layers. In practice, increasing \( n \) improves productivity but may reduce accuracy if the lay becomes too high, compressed or distorted.

A simple practical relationship can be written as:

\( \text{Cutting productivity} \propto \text{Lay height} \times \text{Cutting speed} \)

This does not mean that lay height should always be increased. Very high lays may cause blade deflection, heat build-up, ply displacement and poor edge accuracy. The best cutting method is therefore the one that balances productivity with acceptable cutting quality.

Visual 3: Decision guide showing how production volume, fabric type, lay height and accuracy requirement influence cutting-system selection.

9. Cutting Quality Requirements

The objective of cutting is not only to separate fabric, but to produce accurate garment components. Good cutting should maintain the shape of the pattern, preserve the grain line and ensure that all plies are cut uniformly.

Important cutting quality requirements include clean edges, correct notches, accurate drill marks, uniform component size, minimum fabric distortion and proper bundling. The cut pieces should be easy to identify and should move to sewing without confusion.

Common cutting defects include frayed edges, uneven edges, scorching, notching errors, blade deflection, ply shifting, wrong grain direction and mismatched components. Many of these problems arise not only from the cutting machine but also from poor spreading, incorrect lay height, blunt blades, unsuitable cutting speed or careless handling.

A good cutting room therefore needs control over both equipment and procedure. The cutting machine, blade condition, marker accuracy, spreading quality, lay stability and operator skill all work together to determine the final result.

Conclusion

Different systems of cutting are used in garment manufacturing depending on fabric type, garment design, production volume, accuracy requirement and investment level. Hand shears are suitable for tailoring and sample work. Straight knives are versatile and widely used in production cutting. Round knives are useful for simple shapes and long cutting lines. Band knives provide higher accuracy for shaped components and trimming. Computer-controlled cutting systems offer speed, consistency and repeatability in large-scale production.

The best cutting system is not always the most advanced or expensive system. It is the system that gives the required balance of accuracy, productivity, fabric utilisation and cost for a particular production situation.

Related Reading on Fabric Spreading, Cutting and Garment Manufacturing

• Spreading of the Fabric-1
• spreading of the fabric-2
• Fabric Losses during Spreading
• 8 Things to Remember While Spreading Fabric
• 13 things to ensure while cutting

References

1. Carr, H., & Latham, B. The Technology of Clothing Manufacture. Blackwell Science.
2. Cooklin, G. Introduction to Clothing Manufacture. Blackwell Publishing.
3. Glock, R. E., & Kunz, G. I. Apparel Manufacturing: Sewn Product Analysis. Pearson.
4. Tyler, D. J. Materials Management in Clothing Production. Blackwell Science.
5. Jacob Solinger. Apparel Manufacturing Handbook: Analysis, Principles and Practice. Van Nostrand Reinhold.

General Disclaimer

This article is intended for educational and general textile-learning purposes. Cutting-room practices may vary depending on fabric type, garment category, factory equipment, safety standards and production systems. Readers should use this explanation as a conceptual guide and consult machine manuals, factory procedures and safety instructions before applying any cutting method in production.