Sizing Process in Weaving:
Sizing is a generic term for applying various compounds to warp yarn to bind the fibers in the yarn together and to increase the strength and abrasion resistance of the yarn during weaving. The warp yarns, during weaving, undergo number of stresses and strains due to up and down motion of healds in shedding, beating up by the reed, abrasion while passing through the droppers in warp stop motions, abrasion by heald eyes, reed wires, tension due to the action of let-off and take up operations in weaving. Sizing will help the yarn to withstand the amount of stresses applied on the yarn during the weaving process.
The general process flow of the sizing department in weaving is provided as follows:
Receipt of warp beam from the warping process
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Loading of the warpers beam in the sizing creel
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Size paste preparation with required ingredients
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Sizing and drying of warp yarn and preparation of weavers beam
The main objective of the sizing is to apply the size past on the surface of the yarn. Hence, the size paste preparation and the raw materials used in the paste preparation are one of the primary factors that affect the cost of the sizing process.
The most common ingredients used in the size paste are,
a) Primary ingredients are:
- Adhesives: Starch and starch products like maize starch, tapioca starch, potato starch, sago starch, wheat starch, etc.
- Softeners / lubricants: Commonly used materials to make the adhesive film flexible or pliable. E.g.: Oils and fats, waxes, mutton tallow, oils and emulsions, stearic acid emulsions, vegetable tallow, soaps, sulphated oils and fats, mineral oils, paraffin wax, plasticisers, etc.
- Antiseptics: They are also known as preservatives and are used to protect the yarns susceptible to attack by microbiological organisms, moth and insects and mildew. E.g.: Zinc chloride, copper sulphate, zinc sulphate, sodium silicofluoride, salicylic acid, phenol, cresol and benzoic acid.
b) Secondary ingredients are:
- Humectants: These are basically hygroscopic agents and therefore are also called humectants. They help the sized yarn to regain its moisture and flexibility.
- Antistatics: Though the antistatic agents are under the category of secondary ingredients, they are of importance in the sizing of synthetic hydrophobic materials that are prone to static electricity.
- Weighting agents: These are also known as weightening agents, filling agents, fillers, etc. They help to add weight to the yarn so as to make the fabric get a feel of fullness.
- Brightening/bluing agents: To improve the aesthetic look of the material, they are generally made whiter or given a bluish tinge.
- Wetting agents: In the case of synthetic textile materials such as polyester, nylon etc., and the natural adhesives such as starch cannot wet the fibers, since they are hydrophobic in nature. So, wetting agents are used.
- Antifoaming agents: To reduce the formation of foam in the size box, these agents are used.
Factors Inflecting the Cost of the Sizing Process in Weaving:
Following are the some of the important parameters that influence the cost of the sizing process:
- Cost of raw material used – Size paste ingredient.
- Production capacity of the factory.
- Both direct and indirect labor cost.
- Firewood cost – One of the major expenses in the sizing process, as the boiler is used to heat and generate steam. This steam is channelized to the drying section of the sizing machine, like drying drums.
- Electricity cost – Power is mainly used to run the machine through several motors.
- Overhead expenses – Cost incurred on machine maintenance and electrical and electronic equipments maintenance like temperature sensors, viscosity sensors, thread breakage deductions system, etc.
- Maintenance cost
Calculation of Sizing Cost in Weaving:
Sizing cost of fabric is low for coarse yarn and high for fine yarn. Sizing cost of fabric (excluding cost of sizing chemicals) is generally expressed as cost per unit length. Hence contribution of sizing cost can be calculated as:
**Cost of sizing= cost per unit length x tape length
Cost of sizing chemcials is expressed as cost per unit length of size mixture. The cost per piece of fabric can be calculated as:
**Cost of sizing chemicals per piece length = cost/kg X (warp weight per piece length X size add on %)
Following are the practical examples that explain the various steps involved in the cost calculation of the sizing expenses in weaving.
Example:
A sizing industry received 10 warp beams with 612 ends in each to convert it as a weaver’s beam with a tape length of 42,000 meters. The yarn count of the yarn is noted as 45s Ne. In this order, the sizing factory uses 5 sizing machine operators and 1 helper with a wage of Tk.450/shift and Tk.300/shift respectively. The company works with 2 machines with a speed of 120 meters per minute. Similarly, there are two boiler operators and one chemist working in the boiler and size recipe preparation process with a wage of Tk.420/shift and Tk.480/shift respectively. Further, the factory also incurs an expense of Tk.4.5 for firewood per kilogram of yarn processed. The electricity bill is noted as Tk.0.85/kg, other general overhead expenses are Tk.18,000/month and manager salary is Tk.25,000/month for 30 days. Other raw material costs are listed as shown in Table.
Table: The raw material cost and consumption details for example.
Raw material | 80 Cost/kg in Rs | 180 Total consumption in kg |
Softener | 50 | 100 |
Binder | 60 | 90 |
Antiseptic agent | 180 | 15 |
Lubricant oil | 120 | 25 |
Calculate the cost of sizing process in weaving per kg if the company works 1 shift per day.
Solution:
Tap length = 42,000 meters
Total number of beams = 10
Average production speed = 120 m/min
Total number of machines = 2
……………………………..42,000 meter
No. of shifts = —————————————————-
……………………120 meters/min × 2 machines
= 175 minutes
Since the company works for 1 shift/ day,
……………………..175
No. of days = ——————-
…………………..60 × 8
= 0.365 shifts
Raw material costs:
- Starch: Tk. 80 × 180 = Tk. 14,400
- Binder: Tk. 60 × 90 = Tk.5,400
- Softener: Tk. 50 × 100 = Tk. 5,000
- Lubrication oil: Tk. 120 × 25 = Rs 3,000
- Antiseptic agent: Tk. 180 × 15 = Tk. 2,700
Total raw material cost = Tk.30,500
= 254.17 USD [1 USD = 120 Taka]
Labor costs:
- Sizing machine operator: Tk. 450 × 5 × 0.365 = Tk. 821.25
- Helper: Tk. 300 × 1 × 0.365 = Tk. 109.5
- Chemist: Tk. 480 × 1 × 0.365 = Tk. 175.2
- Boiler operator: Tk. 420 × 2 × 0.365 = Tk. 306.6
Total labor cost = Tk. 1,412.55
= 11.77 USD [1 USD = 120 Taka]
Other Expenses:
The total length of the warp yarn in a single beam = 42,000 meters
Total number of ends/beam = 612
………………………………………Total number of ends for the order × Tape length
Hence total yarn weight = ———————————————————————–
…………………………………………….Yarn count × 1695 (conversion factor)
….6120 × 42,000
= ——————————–
……45 × 1,695
= 3,369.91 Kg
Hence, the electricity cost
- Electricity: Tk. 0.85 × 3,369.91 = Tk. 2,864.42
- Firewood cost: Tk.4.5 × 3,369.91 = Tk.15,164.59
Other overheads:
……………………..18,000
Expenses = Tk. ——————- × 0.365
………………………..30
= Tk. 219
Managers salary = (25000/30) × 0.365 = Tk. 304.165
Total expenses = Tk. 18,552.175
= 154.6 USD [1 USD = 120 Taka]
Total sizing cost = Raw material cost + Labor cost + Other expenses
= Tk.30,500 + Tk. 1,412.55 + Tk. 18,552.175
= Tk. 50,464.725
= 420.54 USD [1 USD = 120 Taka]
……………………….50,464.725
Sizing Cost /kg = ——————–
…………………………3,369.91
= Tk. 14.975
= 0.125 USD [1 USD = 120 Taka]
The cost of sizing process in weaving per kg is 0.125 USD
Conclusion:
Sizing process plays an important role in strengthening warp yarns to withstand the mechanical stresses during weaving operation. Sizing cost in weaving is influenced by several factors, including raw material costs, labor, energy (electricity and firewood), overheads, and machine maintenance. Averagely the cost of sizing process per kg is 0.125 USD. Proper management of these factors is key to minimizing the sizing cost while maintaining fabric quality during weaving.
References:
- Handbook of Textile and Apparel Costing by Dr. R. Rathinamoorthy, Dr. R. Surjit and Dr. K. J.Vishnu Vardhini
- Handbook on Fabric Manufacturing: Grey Fabrics: Preparation, Weaving to Marketing by B. Purushothama
- Textile Engineering – An Introduction Edited by Yasir Nawab