Wednesday, May 25, 2011

MARKER EFFICIENCY; EFFICIENCY MAINTAINED DURING MARKER DESIGN IN GARMENTS PRODUCTION




MARKER EFFICIENCY
Marker efficiency is the important part of garments manufacturing. Direct cost of garments could be utilized by marker efficiency. Salary of a marker planner truly depends upon the capability to increase the marker efficiency.

Marker efficiency is determined by fabric utilization, the percentage of the total fabric that is actually used in garment parts. The area not used in garment parts is waste. Marker efficiency depends on how tightly the pattern pieces fit together within the marker. The total surface area of the pattern pieces is compared to the total area of the marker to calculate the percentage of fabric that is used. This is determined automatically by marker-planning software. If marker-making and marker planning technology is not available, the area of each pattern piece may be determined by a planimeter – a mechanical device that calculates the surface area as the outline of the pattern is traced. Factors that affect marker efficiency are fabric characteristics, shape of the pattern pieces, and grain requirements.

Objectives of marker efficiency:
 -Examine how fabric utilization affects marker efficiency
 -Enumerate the factors affecting material utilization

INTERNATIONAL SOURCING OF GARMENTS


SOURCING CRITERIA AND PROCESS:
Once we are clear about the emergence of the readymade garment industry and its growth as well as India’s contribution to the global trade in garments, we now move forward to yet another important facet, which is of sourcing. At this juncture it is important that we first know what is it that we exactly mean when we say sourcing? Sourcing is basically procuring inventory required for the manufacturing process or it could also refer to procuring finished goods at the best price and of the utmost quality. Quality and Cost are the two major factors that determine most of our buying/sourcing decisions.

GLOBAL MARKETING AND SOURCING:
Global marketing directs goods into multiple foreign markets. The process of directing products into global markets must be approached with considerable care and planning. The aggressiveness, method and speed of the global marketing strategy depends on:
(1.) Whether the firm’s products are known among consumers in the foreign country;
(2.) The customs, laws, and regulations in the foreign country;
(3.) The political stability of the foreign country; and
(4.) The expertise among management of the apparel firm.

The wide variation in customs and trade practices among cultures must be explored before deciding to enter a foreign market.
Exporting means domestically produced goods are sold in foreign markets. Indirect exporting involves selling merchandise through a trading company that specializes in selling domestically produced goods in foreign markets. The primary advantage of indirect exporting is that the manufacturer gains the expertise of an exporting specialist. The greatest disadvantage of indirect exporting is that the manufacturer loses control of the promotion and distribution of the product in the foreign country.
If a manufacturer uses direct exporting, the goods are sold by the domestic
Objectives of international sourcing of garments:
 -Enumerate the sourcing criteria
 -Understand the sourcing process
 -Examine the sourcing operations and flow

manufacturer’s sales representatives to retail buyers from a foreign country. Direct exporting gives a firm more control over the distribution of a product, but it also requires more expertise among the firm’s management and sales representatives. Trade missions into foreign countries are sometimes organized by industry trade associations and local or state governments to establish exporting systems that many firms can then use. Sales might also be accomplished through export fairs or markets held within the country or abroad, where foreign buyers are invited to purchase goods.
Global sourcing determines where materials come from and/or where apparel is made that enters domestic markets. For the most part, global marketing results in exporting, while global sourcing results in importing. Global sourcing has become common practice for most apparel firms.

 SOURCING CRITERIA, BUYING OPERATIONS AND FLOWS 
The buying operations are generally guided by the overall policies and philosophy of the companies and macro-environmental variables. The specific inputs, which influence these operations, are:
 -The fashion viewpoint of the stores,
 -Price-points,
 -Promotion methods,
 -Organizational structure,
 -Retailing mix, and
 -Geographical locations.

The import and sourcing policy and import decisions are taken, by and large, by the corporate office and the buying operations are delegated to buyers/merchandisers based on the overall budget, open-to-buy (the budget available for purchase), turnover ratios, lead time, retail square footage productivity, sales expectation, mark-up, margin and profitability.

In a typical retailer structure, for example, considering a department store, there are separate merchandise managers for different product groups and divisional merchandise managers for major groups of products and buyers for different items. The import decision and the policy implication are generally handled by the headquarters of the companies, where the open-to-buy budgets of various product groups are divided among different countries based on quota availability and other sourcing criteria. In some cases, the actual budget for buying from a region is given for instance, to the companies’ office in Hong Kong and then that office would decide whether to buy from India, Sri Lanka, Bangladesh etc., for example, and how much of quantity allocation to make. It is very clear, therefore, that knowing the distribution channels, understanding the type of retail outlets involved in marketing, sourcing systems of buyers and the practices and policies of the company become very critical in improving exports and unit value realization. The quality standards and the communication of the same are also linked to the type of sourcing systems and buying network available to the company in question, whether it is department stores, specialty chains or 'brand-manufacturer'. For instance, in the case of Liz Claiborne, as the company sources from 60 countries, the quality standards are centralized and communicated to each country representative, whose responsibility it then becomes to implement the quality standards. Even the computation of CMT, etc. is standardized. The retail sourcing decisions will depend on the type of retailer (department store, specialty chains, catalogue houses, etc.) and the type of consumers they represent.

The retailers have merchandisers and buyers who are generally in charge of the buying operations. The larger retailers have import departments for general import decisions and buying departments for merchandise development and selection. Certain companies develop specialized sourcing arms, as this activity is the key to successful retailing, by providing the right merchandise, in the right quality, at the right channel and at the right price. For instance, the Geoffrey Beene in the USA has 'Triburg' in New Delhi as the sourcing arm whereas C & A, Brussels has 'Mondial lnternational' as the sourcing arm in India. But there are companies like Hennes & Mauritiz (H&M) from Sweden and GAP from USA, which have set up full-fledged buying offices in India. Department stores like Macy has also set up their own buying office in other countries as in India. In another instance, Hertie, the import policy decisions are taken in Frankfurt but buying and merchandising decisions are taken at their Hong Kong office, which handles the sourcing from India and other South-Asian supplying countries. In Sri Lanka, many buyers like Mast Industries, USA have entered into three-way or two-way joint ventures with manufacturing factories. The exporters have to understand the difference in operations in order to develop competitive advantage. For instance, the ability required by an exporter to satisfy a mail order house is very different from the ability required to satisfy a department store or a brand-manufacturer.
Quick response, price performance ratio etc. are very important for the buyers, though again it is a function of the type of merchandise and the channels. The price quality-delivery-fashion performance expectations are guided by the nature of the retail operation. For instance, department stores and specialty stores have private label and national brands in their merchandise groups. A private label is a brand introduced by the stores in order to improve their profitability, fashion orientation and life-style positioning. Examples of these are Aeropostale and ThorntonBay by Macy's, Bloomies by Bloomingdale, St. Michael by Marks and Spencer and STOP! by Shoppers’ Stop. A national brand is one, which is marketed by brand manufacturers, like Levis, Seidensticker or Liz Claiborne. The private labels may work on more seasons and the national brands on fewer seasons. Likewise, importers and wholesalers also have their own wholesale brands. The specialty chains, department stores and importer-wholesalers have the option of getting fabrics from the Far-East, Pacific Rim, China, etc. and the manufacture of garments can be done again in the Far-East, Latin America, East Germany, C.I.S. countries, South-East Asia, South Asia and such other low-cost countries. This again involves backward pricing (determining the f.o.b. price based on the ultimate selling price at the retail level) based on the type of merchandise, level of labor cost involved, fabric availability, lead time requirements, possibility of fill-ins and replenishment and such other factors. Thus, the sources of competitive advantage exist in all the links of the value chain.

The basic requirements of a fashion retailer could be quick response, small quantities and flexibility in assortments. These characteristics when turned into specific sourcing criteria could mean price-performance ratio, fashion-price or quality-price-speed expectations. However, the objectives in most cases are:
1. Reduced inventory
2. Maximize profits/square footage sales
3. Optimize seasonal sales
4. Obtaining exclusivity for building customer loyalty.

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CUTTING SYSTEMS IN GARMENTS FACTORY; AUTOMATED, NUMERICALLY CONTROLLED



Automated cutting is the best system for fabric lay cutting in garments. Automated cutting more faster than manual cutting system. Automated cutting system is operated by computerized numerically controlled cutting system. Required low labor cost and the lowest man power for automated cutting system.

Objectives of Automated cutting system:
 -Equipments and their operations
 -Recent development in equipments and techniques

 The four types of automated cutting systems are:
(I) blade cutting,
(II) Laser cutting,
(III) Water jet cutting, and
(IV) Plasma jet cutting.

Electronic microchips control the cutting device, travel pattern, and speed. Computer-generated markers are stored and used to guide the operation of the cutting head. Printed markers are not required for cutting but may be used to assist with bundling. The primary advantage of computerized cutting systems is the accuracy of the process.

Automatic Blade Cutting is the most highly developed and widely used computerized cutting system. Systems are specific to the standard volume to be cut. Numerically controlled knives cut multiple plies with great accuracy and speed. Information can be downloaded directly to the cutting system when needed. Easy data entry and instant communication with the main control unit allow technicians to preprogram multi-step commands, set parameters, and start the process with a single keystroke.

The central control unit operates the components of the system such as the cutting head, cutter carriage, knife sharpening, and conveyorized cutting table. A cutting head is a sophisticated mechanical component with the capacity to cut, mark, and drill as dictated by the computer. Automatic knife sharpening is done at preset intervals during the cutting operation. The cutter carriage moves the cutting head and provides lengthwise and crosswise motion during the cutting operation. The reciprocating blade can be adjusted to the height of the spread and density of the fabric. Knife speed automatically adjusts to the forward speed of the cutting head. As the cutting head slows for corners, curves, or notches, the reciprocating blade also slows to reduce heat and possible fusing. Most reciprocating knife systems use a vacuum to hold down the fabric. Placement of plastic film over a spread helps compress the fabric into a firm stationary lay-up when the vacuum is applies. The effect of the vacuum is to reduce the height of the spread and eliminate fabric movement during cutting. An intensified vacuum force is automatically applied to the area directly under the knife to further restrict material shifting

Laser Cutting focuses a powerful beam of light projected onto a minute area to cut fabric by vaporization. The fine, V-shaped beam is only 0.004 of an inch. The beam cuts without pressure on the fabric, which is a major advantage for some types of fabric. The fabric remains immobile during the cutting operation.

Lasers cut with incredible speed (twice that of automatic knife cutting), accuracy, and multidirectional ability, but with some heat emission. Laser-cut edges are sharp and clean. The heat produced tends to seal fabric edges, which can be an advantage for fabric that ravels and a disadvantage for cutting multiple plies as edges may fuse together. Laser-cut garment parts are easier to assemble, as they are consistent in size with smooth sharp edges to align.

Water Jet Cutting is another computer-operated, multidirectional method that has limited usage at this time. Water jet cutting is performed by propelling a tiny jet of water (0.0010-0.0015 inch) through fabric at very high pressure (70,000 pounds per square inch). The forward edge of the jet stream shears the fabric as it moves along the cutting line but does not wet the fabric, generate airborne contaminant, or exert an appreciable force on the ma-terial. The water jet will cut multiple plies without fusing, but it may fray and tangle the yarns of some fabrics, which makes it difficult to separate the plies. It is used when heat build up must be avoided and water absorption is not important. At the present time its use is limited to cutting leather and vinyl fabrics.

Plasma Jet Cutting is a computer-operated, high-speed, single-ply cutting device that offers many of the same features of a laser cutter but at a lower price. Along with the plasma jet cutting system, Investronica has developed a Matching System for automatic matching and cutting of striped, checked, or printed fabric. A TV camera reads the fabric on the conveyor, and a digital image processor decides the best way to match and layout the pattern pieces based on determined matching rules. Matches can be made among different prints, selvages, and fabric characteristics. This system eliminates recutting parts for more precise matching.

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Tuesday, May 24, 2011

GARMENTS SEWING MACHINE FUNDAMENTALS- PRINCIPLES OF STITCHING (MECHANIZATION PROCSS)




Sewing machine is an important part of apparel and garments manufacturing technology. Production of garments factory depends on the performance of sewing machine and principles of stitching. Principles of stitching and perfection of stitching depends on the quality of sewing machine.

Mechanization is the process of replacing human labor with machines. Mechanization of the garments sewing process encouraged mass production of apparel garments product. Garments sewing that had long been performed by hand sewing machine could be done more rapidly by garments sewing machine. By about 1900, most garments sewing processes could be performed by machine

Automation is a state of operating without external influence or control. In manufacturing of garments and apparels it is often viewed as highly desirable because it eliminates the potential for garments workers error. Automated garments sewing systems are capable of feeding themselves cut garments parts from a stack, completing multiple sewing tasks, and delivering finished parts of garments. Automated equipment for garments sewing may be cost effective for some apparel manufacturers, while the high costs of acquisition, installation, and maintenance are prohibitive to others.

Robotics is the most advanced form of automation in garments sewing operation. Robots are computerized, reprogrammable, multifunctional manipulators designed to move materials, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks. Flexible reprogrammability is one of the hallmarks of robotic automation. This manufacturing flexibility differentiates robotics from fixed-purpose, hard-wired automation, which has to be torn apart and reconfigured for every new application.

Garments sewing and Apparel pressing equipment may be either general or special-purpose. General-purpose garments sewing machines are manually operated by garments worker and can perform a variety of sewing operations. Special-purpose garments sewing machines are designed to perform a specific garments related or sewing related operation and more likely to be semiautomatic or automatic machine.













 





Objectives of garments sewing machine:
 -Discuss issues related to equipment selection
 -Explain mechanization and automation relative to special- and general-purpose garments sewing machines
 -Examine the basic components of garments sewing machines and work aids

GARMENTS SEWING MACHINE FUNDAMENTALS:

A basic garments sewing machine or apparel sewing head, as it is sometimes called, consists of the fundamental parts required to form a stitch, sew a seam, or perform a specific garments sewing operation. The major components of a basic garments sewing machine include a sewing casting, a machine lubrication system, a stitch-forming system, and a garments feed system. The speed at which a sewing machine can operate depends on the engineering of the garments machine’s components.

The Sewing Casting:

The sewing machine casting is the metal form that provides the exterior shape of the garments machine. Shapes vary with the bed type, the garments sewing function that is to be performed, and how piece goods are to be presented to the needle. The casting houses the internal workings, such as the gears, cams and shafts, that operate the stitching and feeding mechanisms of the sewing machine.

Bed Type:
The bed is the lower portion of the sewing machine under which the feed mechanisms and loopers are located. Sewing machines are frequently described by bed types.

Different Types of Machine Beds:


Types of Garments Sewing Machine
Sewing
Stitch Type
Features and Uses
Flat bed sewing machine (basis type)
Lockstitch sewing, Chain stitch sewing
The large working area allows a wide range of sewing application; the material can easily be guided around the needle and the presser foot. This basic type garments sewing machine used for all kinds of flat sewing operation.
Raised bed sewing machine
Lockstitch sewing, Chain stitch sewing
The bedplate is in the form of a plinth. It facilitates the assembly of pre-sewn parts and is especially suitable for the fitting of accessories and special attachments. This is the basic form for various specialized garments sewing machines such as buttonholers.
Post bed sewing machine
Lockstitch sewing, Chain stitch sewing
This type of sewing machine has an increased working height. Special sewing applications are found in the working of three-dimensional products. e.g. shoes and bags. The post makes it easier to work on tight curves and corners, to sew in sleeves and to complete large, half-assembled products.
Cylinder bed sewing machine
Lockstitch, Chain stitch
This type of garments sewing machine has an increased working height and a bed in the shape of a horizontal arm. It is especially suitable for sewing on tubular parts, such as cuffs, sleeves, and trouser legs, and also for button sewing and bar tacking.
This sewing machine is used extensively in the making of clothing from knitted fabrics.
Side bed machine
Chain stitch, Over-edge
Machines which are specialized for sewing at edges need only a small working area

CUTTING AND CUTTING ELEMENT OF GARMENTS IN APPAREL FACTORY




Cutting is the production process of separating (sectioning, carving, severing) a spread into garment parts that are the precise size and shape of the pattern pieces on a marker. The cutting process may also involve transferring marks and notches from the marker to garment parts to assist operators in sewing. Chopping or sectioning a spread into blocks of piece goods may precede precision cutting of individual pattern shapes. This is often done to allow for accurate matching of fabric design or easier manipulation of a cutting knife.
CUTTING AND CUTTING ELEMENT OF GARMENTS IN APPAREL FACTORY

Fabric pieces may be cut to predetermined lengths for matching patterns or for additional processing such as screen printing. Spreads of plaid fabrics may be presectioned into blocks so the design of the fabric can be perfectly matched before cutting to the shape of the pattern piece. Presectioned pieces may also be garment parts knitted to specific finished lengths such as sweater bodies. Presectioned pieces such as leather or other specialty fabrics may be and cut as a single ply or laid up and cut as a multiple-ply spread. 


Objectives of cutting:
 -Understanding of the cutting process
 -Cutting equipments and their operations

Cutting often is carried out in two stages: rough cutting (separating the individual pieces) and the final cutting (accurate cutting of the individual shapes). Different types of cutting tools have different degrees of precision.

PORTABLE CUTTING KNIVES:
Portable knives can be moved to and through a spread by an operator. There are two main types of portable knives:
(i) vertical reciprocating straight knives and (ii) round knives. Structurally and mechanically the two types of machines share many similarities. Structurally, both types of knives have a base plate, power system, handle, cutting blade, sharpening device, and blade guard. Round knives operate with a one-way thrust as the circular blade makes contact with the fabric, and vertical knives cut with an up-and-down action. Circular cutters and straight knives are pushed by hand through the stationary material.

CIRCULAR CUTTERS:
Circular cutting tools use a rotating circular blade. The smallest devices (power shears) is used for cutting single ply lays and for cutting fabric plies to length during manual spreading. Depending on the size of the device it is possible to cut to a depth of about 10mm. The larger circular cutter is used mainly for dividing a lay into sections. It is suitable only for cutting in straight lines or very gradual curves, in depths of about 150mm.

STRAIGHT KNIVES:
A straight knife cutter has a vertical blade, which reciprocates up and down. It is capable of both coarse and precise cutting to a depth of about 300mm. Corners and curves can be cut accurately. Since all of the layers are cut at the same place (unlike a circular cutter), and provided that the knife is held vertical, then all of the pieces cut from a lay are identical.
Vertical straight knives with reciprocating blades are the most versatile and commonly used cutting devices. Reciprocating blades have a vertical cutting action. Blades vary in length from 6 to 14 inches. Blade length and the adjustable height of the blade guard are factors in determining the spread depth that can be cut. The 90-degree angle of the narrow, thin blade to the cutting surface makes this knife a good choice for accurately cutting sharp corners, angles, and curves.
Vertical straight knife machines make only lateral cuts into a spread therefore cannot be used to cut out areas from the center of garment parts.

Basic Components of Portable Knives:
Blades are mounted in a vertical position at a 90-degree angle to the cutting surface. Blades vary in shape, size, cutting action, and fineness of the cutting edge. A straight blade contacts the spread at a 90-degree angle; assuming the blade and spread are kept vertical, all plies are cut at the same time. A rotary blade does not cut all plies evenly at the same time. A round blade contacts the spread at an angle; thus, the top ply is cut before the bottom ply.

(i) Knife blades can have a major affect on the quality of the cut. Factors that affect the performance of a blade are the blade edge, surface texture of the blade, coarseness or fineness of the blade edge, and blade composition. Blade edges may be straight with a flat surface, saw-toothed, serrated, or wavy with a striated surface. Straightedge blades with a flat surface are general-purpose and the most widely used, while the other types are more specific to certain types of fabrics. Striated blades are used to reduce heat buildup during cutting, wavy edges are used for plastics and vinyls, and saw-type blades are use for cutting canvas.

(ii) The base plate is the foundation that supports and helps balance the cutting mechanism. Bases vary in shape and size, depending on the size and weight of the knife it supports and the maneuverability needed. The base plate guides the knife in relation to the table surface and elevates the spread off the cutting table for contact with the blade. Base plates are supported by bearing rollers to facilitate maneuverability and ease of movement. Edges of the plate are sloped and the front curved to easily slide under the bottom ply and provide less fabric distortion and drag as it is maneuvered during cutting. The base plate helps maintain the position of the blade at a 90-degree pitch.

(iii) The power system controls the motor and the potential cutting speed. The amount of power needed to cut a spread depends on the height of the spread and the density of the fabric to be cut. The horsepower of the motor determines the amount of thrust or cutting power of the blade. Higher speeds allow operators to move knives faster. Greater horsepower increases machine power but it also may increase weight of the motor, which must be balanced by the blade housing and base plate. Larger, more powerful knives, which may weigh approximately 35 pounds, are often more cumbersome, heavier, and harder to manipulate and maneuver. Motors with variable speeds provide more versatility.

(iv) Sharpening devices appropriate for the specific blade type are found on almost all mechanized cutting equipment. Blades dull quickly when cutting deep spread or dense fabric. As a blade becomes dull, it creates friction and may cause rough, frayed, or fused edges. Sharpening devices may be stone or emery wheels or abrasive belt sharpeners. Cutting blades are sharpened frequently during the cutting operation simply by touching the control.

(v) All manually operated cutting devices have a handle for the operator to grip, guide, and propel the knife through the spread. The operator's other hand is used to stabilize the plies ahead of the knife to prevent bunching of fabric.

(vi) A blade guard, when positioned at spread height, rests on the top ply to help stabilize the spread and to protect the operator's hand. Metal mesh gloves are available as a safety device for cutters using vertical knives.

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THE SPREADING PROCESS & SPREADING MODES OF FABRIC IN A GARMENTS FACTORY




Spreading process and spreading mode is very important terms of garments manufacturing. Quality of garments depends upon the spreading process and spreading mode. Manual spreading process is slower than automatic spreading process. Quality of spreading process is depends upon operator quality in a garments.

THE SPREADING PROCESS & SPREADING MODES OF FABRIC IN A GARMENTS FACTORY

Spreading is the process of superimposing lengths of fabric on a spreading table of garments, cutting table, or specially designed surface in preparation for the cutting process. A spread or lay-up is the total amount of fabric prepared for a single marker. A spreading may consist of a single or multiple plies. The height of a lay-up or spreading is limited by fabric characteristics size of the order to be cut, cutting method, and the vertical capacity of the spreader. The number off plies in a spread may range from 1 to 300.

Spreading may be done manually or by computer-controlled machines. One person or two, depending on the width and type of fabric, type of equipment, and size of spread, may be involved with the spreading process. Two people may be used for manual spreading unless the spread is very short. One person may work each side of the table in order to keep the fabric flat, smooth, and tension-free. With automatic spreading, the equipment controls the tension, fabric placement, and rate of travel. The spreading operator monitors the process and removes fabric flaws as needed.

Objectives of spreading process:
 -Understanding the process of fabric spreading
 -Factors affecting spreading
 -Face and nap of the fabric
 THE SPREADING PROCESS
Two aspects of spreading that affect spreading efficiency are the setup and actual layout of fabric. Setup involves loading and threading fabric through the spreader and positioning the machine and related equipment. The actual process of spreading involves laying out fabric in the desired number of layers. Fabric may be spread face up, face down, or face-to-face.

SPREADING MODES
A spreading mode is the manner in which fabric plies are laid out for cutting. The spreading mode is determined by the fabric characteristics, quality standards of the firm, and available equipment. Two fabric characteristics that determine the spreading mode are the direction of fabric and the direction of the fabric nap.

Direction of Fabric Nap
A second consideration in selecting the spreading mode relates to the direction of the fabric nap. Placement of the nap may be nap-one-way (N/OW) or nap-up-and-down (N/U/D).

Asymmetric and directional fabrics must have the nap running the same direction, nap-one-way (N/O/W). This spreading mode is the most time-consuming to lay-up but it generally produces the best quality. N/O/W fabrics may be spread F/F and F/O/W. if napped fabrics are to be positioned F/F the fabric needs to be cut and the roll turned at the end of each ply so the nap will lay in the same direction on facing plies. This is suitable for directional fabrics and to pair garment parts for the sewing operation. This is sometimes referred to as pair spreading.

Symmetric, nondirectional fabrics allow flexibility for spreading. These fabrics can be spread with the nap running both up and down the spread. This spreading mode is called nap-up-and-down (N/U/D). This type of fabric may be spread face-to-face or face-one-way with the nap running up and down.

Direction of Fabric Face
The fabric face may be positioned in two ways: face-to-face (F/F) or with all plies facing-one-way (F/O/W), face up or face down. Face-to-face (F/F) spreading may be continuous as the spreader moves up and down the table. This is the fastest method of spreading, the least costly, and generally results in the lowest quality. With this method of spreading the face is up on one ply and down on the next ply as the spreader goes back and forth. Often symmetrical, non directional fabrics are spread continuously, which places alternate plies face-to-face or back-to-back. Quality is affected because the operator is only able to monitor the face of fabric half the time.

F/O/W spreads, face up or down, are more time-consuming and expensive because fabric must be cut at each end of the spread and the new end repositioned. If a rotating turntable is used to turn the fabric roll 180 degrees at the end of each ply, the fabric can be spread from both ends of the table without a wasted trip. F/O/W spreading may be done with the fabric face up or face down. When the fabric faces up, the operator is able to monitor the face for flaws and imperfections as the fabric is being unrolled. This is particularly helpful when spreading prints. Pile fabrics, corduroy and velvet, are often spread face down, other high-quality fabrics are spread face up.

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GARMENTS PRODUCTION PROCESSES OF APPAREL FACTORY


Objectives of garments production process:
  -Examine garments production strategies and concepts
  -Explore the relationship among production standards, capacity, and production planning
  -Examine factors that impact productivity and measures of productivity.

The plant and production system create the environment for executing production processes. A process is a procedure required to convert materials into a specific product or style. The type and sequence of garments production processes required for conversion is unique to each style. Use of inputs to the process (including materials, methods, machines, and skills) is determined by the expected output.

Process Analysis and Control:
Process analysis begins with examination of each style to determine its requirements for production. Style requirements are discussed at product planning meetings, determined through analysis of samples and specifications, and evaluated based on a firm’s standard operating procedures and cost constraints. Production skills, production time, equipment needed, and the anticipated volume are evaluated for each style.

The basic breakdown of operations for a style is often identified by technical designers while engineers develop detailed specifications, methods, and production standards necessary for consistently executing the processes. An operation is one of the steps in a process that must be completed to convert materials into a finished garment. An operation breakdown is a sequential list of all the operations involved in cutting, sewing, and finishing a garment, component or style.

Production Standards:
Production Standards are a means of controlling time and labor costs by establishing a reasonable time for completing each operation. They provide a basis for determining whether the actual production time and costs are acceptable. Production standards are used to plan and schedule production, analyze capacity, and serve as performance criteria for workers. Production standards provide management with a numerical base (quantitative base) for making decisions and managing plant production. A production standard reflects the ‘Normal’ time required to complete one operation or cycle using a specified method that will provide the expected quality. In comparing actual performance with a production standard, trouble spots can be identified, productivity evaluated, and adjustments can be made.

Labor Efficiency for production development:

Labor efficiency is ratio of work accomplished versus the work expected to be accomplished. The work accomplished is provided by the operator’s output sheet and the work expected to be accomplished is provided by the production standard.

Labor Performance in production field:
Combining labor efficiency with labor utilization provides the basis for the labor performance report. Labor performance can be loosely translated as labor productivity.

Performance = efficiency x utilization

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APPAREL GARMENTS PRODUCTION SYSTEMS




Apparel Garments production is the last process of textile production. Garments production is the heart of textile production. Garments production includes the production of production of finished apparel garments. An apparel garments production system is an integration of materials handling, production processes, personnel, and equipment that directs work flow and generates finished garments products. Three types of production systems commonly used to mass produce apparel are:


-Progressive bundle system
-Unit Production System
-Modular Garments Production System
-Combined garments Production System

Each system of garments production requires an appropriate management philosophy, materials handling methods, floor layout for garments spreading, and employee training. Firms may combine or adapt these systems to meet their specific garments production needs. Firms may use only one production system, a combination of systems for one product line, or different systems for different product lines in the same plant.

Objectives of garments production system:
 -Examine the characteristics of different types of apparel production systems
 -Compare and contrast the different production systems
 -Evaluate and critically compare the use of systems in different contexts
 -Summarize the benefits of the different garments production systems 

Progressive Bundle Production System:
The progressive bundle system of apparel  production is called from the bundles of garment parts that are forward sequentially from process to process. It is needed to complete a specific operation or component. For example neck join is a single process, for bundle system an operator will join neck of full bundle then it will forward to another operator.  READ MORE(.........)


Unit Production System
A unit production system is a type of line feeding that uses an overhead transporter system to forward apparel parts from work station to work station for assembly. All the components for a single garment are advanced through the production line together by means of a hanging carrier that travels along an overhead conveyor. READ MORE(...........)

Modular Garments Production System
A modular garments production system is a contained, manageable work unit that includes an empowered work team, equipment, and work to be executed. Modules frequently operate as mini-factories with teams responsible for group goals and self-management. The number of teams in a plant varies with the size and needs of the firm and product line in garments. READ MORE(..........)

Combinations of Garments Production Systems
Some firms may use the progressive bundle system for producing small parts combined with modular production for garment assembly. This reduces the investment in specialized equipment and reduces the team size needed. Some industry consultants believe that a modular system combined with a unit production system provides the most flexibility, fastest throughput, and most consistent quality. This would be particularly useful for large items such as coveralls or heavy coats. The UPS would move the garment instead of the operators. Each manufacturer needs to determine what is best for its product line and production requirements.

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Tuesday, March 29, 2011

Knitted fabric properties






Wales per cm of knitted fabric
Wales per cm is a very much important properties knitted fabric. Wales are perpendicular lines of loop along the knitted fabric length. Wales is the column of loops along the length of the fabric. Wales determine the width of the knitted fabric and are measured as Wales per centimeter. The number of Wales per cm is depend the types of knitted fabric. For examples, 10 wales per cm is taken for single jersey knitted fabric and 7 wales per cm is taken for rib fabric knitting, it is measured along the course direction by using counting glass and needle.
  
Process sequence for measuring wales per cm of knitted fabric:

· When loop transfer occurs it is possible to transfer a wale A to another B and to recommence knitting with the second needle in which case more than one needle will have produced intermeshed loops in the same wale. 
· In warp knitting a wale can be produced from the same yarn if the same guide laps the same needle at successive knitting cycles . 
· Wales are connected together across the width of the fabric by sinker loop(weft Knitting) or under laps (Warp knitting) 
· Wales show most clearly on the technical face and technical back of single needle bed fabric. 
· For single jersey fabric wales show on face side as V shape and from back side as half circle.

Course per cm of knitted fabric:
A course is a predominantly horizontal raw of needle loops produced by adjacent needle during the same knitting cycles. Course is a row of loops across the width of fabric. A course determines the length of fabric and measured as course per centimeter. The number of course per centimeter is called course/cm. It Is measured along the wale direction by using counting glass and needle.

Monday, March 28, 2011

REACTIVE DYES FOR WOOL FIBRES

Fig: Types of reactive dyes for wool

 
Fig: Reactions of bromoacrylamido reactive dyes with wool
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BATCH DYEING OF WOOL WITH REACTIVE DYES


Wool fibre is a animal protein fibre. The chemical construction of the wool fibre is very much complex but contains a reactive functional group that used to react with the reactive group of reactive dyes. The somewhat late development of fibre-reactive dyes was partly caused by a lack of appreciation of the considerable reactivity of made of cellulose fibres (specially cotton fibre) or proteins fibres (specially wool fibre).

A number of dyes developed for wool with 2-sulphatoethylsulphone or chloroacetylamino groups were not immediately recognised as reactive dyes. In fact, the development of reactive dyes really started with the introduction of the Procion reactive dyes for cotton by ICI in 1955. Despite the many possible reactive groups in reactive dyes capable of covalent bond formation with nucleophilic groups in wool, only a limited number of types of reactive dye have been commercially successful. Figure-1 shows the major types of reactive groups. The dye chromophores are essentially those used for cotton fibre reactive dyeing. The most important reactive groups in wool fibre are all nucleophilic and are found mainly in the side-chains of amino acid residues.






































They are, in order of decreasing reactivity, thiol (the –SH of cysteine), amino (–NH– and –NH2 of say histidine and lysine) and hydroxyl groups (–OH of serine or tyrosine). Difluorochloropyrimidines undergo aromatic nucleophilic substitution of one or both fluorine atoms, the fluorine between the two nitrogen atoms being the most reactive. Bromoacrylamido groups are stable in boiling water at pH 7 and react by both nucleophilic addition to the double bond and nucleophilic substitution of the bromine atom. They can form a three-membered aziridine ring that can react further with the protein fibre resulting in a new crosslink. The actual reactive dyes are probably dibromopropionamides, which eliminate HBr on dissolving in hot water. Methyltaurine-ethylsulphones and 2 sulphatoethylsulphones form the vinyl sulphone reactive group of reactive dyes relatively slowly at pH 5–6 (1 h at the boil). This allows some textile levelling during dyeing before the vinyl sulphone dyes reacts with the wool fibre and becomes immobilized. 

This is useful in hank and winch dyeing where the liquor/goods interchange is less favourable. In fact, all commercial reactive dyes for wool have absorption rates that are greater than the rate of reaction with the wool fibre to allow some migration. Chloroacetylamino groups (–NHCOCH2Cl) react by an SN2 mechanism (Scheme 16.5). Wool reactive dyes are applied like acid dyes in weakly acidic solution. The degree of exhaustion and fixation are usually very high and clearing of unfixed dye from the goods may only be needed for deep shades. Reactive dyes for wool tend to be unlevel dyeing and are prone to give skittery dyeings. They are used more on loose fibre and slubbing than on piece goods, where they accentuate fibre nonuniformity and poor, uneven fabric preparation. A number of amphoteric or weakly cationic auxiliary products are available to assist level dyeing. Despite their good light fastness and very good washing fastness, they are still not widely used, partly because of their high cost. Red to maroon shades are very popular but there are no black reactive dyes available that can match the chrome blacks on wool fibre.
1. J Shore, in Cellulosics Dyeing, J Shore, Ed (Bradford: SDC, 1995).
2. D M Lewis, in Wool Dyeing, D M Lewis, Ed (Bradford: SDC, 1992).
3. A H M Renfrew, Adv. Colour Sci. Technol., 1 (1998) 12.
4. A H M Renfrew and J A Taylor, Rev. Prog. Coloration, 20 (1990) 1.
5. D A S Phillips, Adv. Colour Sci. Technol., 1 (1998) 1.
6. J A Taylor, Rev. Prog. Coloration, 30 (2000) 93

Informative articles on Dye reactivity, Application and Storage of Reactive dyes



Dye reactivity is very important terms for dyeing cellulose fibre. Shed of dyed textile fabric directly depend on the reactivity of reactive group. Highly reactive group of reactive dyes makes strong covalent bond with cotton fibre structure. The reactive groups of different types of reactive dyes have different chemical structures and show a wide range of reactivities. They were originally divided into cold- and hot-dyeing types but many current ranges would be better called warm dyeing. The most reactive types, such as DCT reactive dyes, are applied at lower temperatures (20–40 °C) and for dyeing process only require a weak alkali such as NaHCO3 or Na2CO3 for fixation. The less reactive types, such as MCT dyes required higher temperatures (80–90 °C) and stronger alkalis such as Na2CO3 plus NaOH. Many reactive dyes manufacturers now market several ranges of reactive dyes for cotton fibre , each with its own particular recommended dyeing procedure.

Gives some typical examples of reactive dyes based on the type of reactive grouping.
 
Reactive group
Commercial name of reactive dyes
Reactivity
Exhaust dyeing
temperature (°C)
DCT
Procion MX (BASF)
high
25–40
MCT

Procion H (BASF) Basilen (BASF)
Cibacron (Ciba)
low
80–85
MFT
Cibacron F (Ciba)
moderate
40–60
DCQ
Levafix E (DyStar)
low
50–70
DFCP
Drimarene K (Clariant)
Levafix E-A (DyStar)
moderate to high
30–50
VS

Remazol (DyStar)
moderate
40–60
TCP
Drimarene X (Clariant)
low
80–95

NT
Kayacelon React
(Nippon Kayaku)
moderate to high
100–130
  *




Because most reactive dyes are prone to hydrolysis, their handling and use requires care. Most of the reactive dyes are readily water-soluble dye and the dye solution in dye bath is prepared in the usual way by pasting with water and then adding more water. The temperature of the water used depends upon the ease of solution and the reactivity of the dye. Hot water is not recommended for dissolving dyes of high reactivity, because of the risk of hydrolysis of the reactive group, but is suitable for the less reactive types.
 Special care must be taken for storing reactive dyes. Highly reactive dyes could be react with air. Once the dye solution of reactive dye has been prepared, it cannot be stored for later use without some risk of hydrolysis of the reactive group of reactive dyes. This decreases its fixation ability after dyeing and is a particular problem with the most reactive types of dye. Dyes containing a 2 sulphatoethylsulphone group, however, can be dissolved in neutral water at the boil without risk of hydrolysis. Formation of the reactive vinyl sulphone group requires the addition of alkali. Reactive dyes for printing are usually dyes of low reactivity so that the print paste can be stored for some time at room temperature without deterioration from hydrolysis of the reactive group. Reactive dyes of low reactivity and relatively high substantivity are valuable for dyeing using long (high) liquor ratios, using a winch machine for knitted fabric and twill tape dyeing. Exhaust dyeing method with low reactivity of reactive dyes at the higher temperatures required for fixation allows better penetration of the dyes into the cotton fibres. For continuous dyeing with reactive dyes stabilised liquid forms are available. Although these contain special pH buffers and stabilisers to minimise the hydrolysis reaction, they only have a limited shelf life. Many commercial reactive dyes are dusty powders but all physical forms must be handled with care. These dyes react with the amino groups in proteins in the skin and on mucous surfaces. Inhalation of the dust is dangerous and a dust mask is obligatory during handling. Reactive dye powders and grains are sometimes hygroscopic and drums must be carefully re-sealed. Most reactive dyes have a limited storage period, after which some deterioration can be expected. Standardisation and comparison of reactive dye powders or liquids cannot be done by the usual spectrophotometric procedure involving absorbance measurements of standard solutions. Both the reactive dye and its hydrolysed form are evenly coloured, but only the former is capable of reaction with the cellulose fibre during dyeing. Therefore, dyeing must be prepared and their colors compared with standard dyeings. Chromatographic techniques usually allow separation and quantitative measurement of the relative amounts of a reactive dye and its hydrolysis product in a given dye.
 
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Structural discussion of reactive dyes those suitable for cotton fibre



There are different types of reactive dyes that are usually compatible with cotton fibre. But molecular structure of cellolusic cotton fibre is complex. So the dyes which have more reactivity is suitable for that complex structure of cotton fibre. The molecular structures of reactive dyes resemble those of acid and simple direct cotton fibre dyes, but with an added reactive group. Usually the structure of  reactive dye assemble with azo anthraquinone  triphenodioxazine or copper phthalocyanine chromophores. The key structural features of a reactive dye are the chromophoric system, the sulphonate groups for water solubility, the reactive group, and the bridging group that attaches the reactive group either directly to the chromophore or to some other part of the reactive dye molecule. Each of these structural features can influence the dyeing and fastness properties of dyed textile material. Most of the commercial reactive dyes have a complete gamut of colours, many of which are particularly bright in color. Reactive dyes often have quite simple structures that can be synthesised with a minimum of coloured isomers and biproducts that tend to dull the shade of the more complex polyazo direct dyes. Some colours are difficult to obtain with simple chromophores. Dark blue and navy reactive dyes are often rather dull copper complexes of azo dyes and the production of bright green reactive dyes usually make. A wide range of possible fibre-reactive groups has been examined and evaluated by the dyestuff manufacturers. The final choices for commercial reactive dyes are limited by a number of constraints. The reactive group must exhibit adequate reactivity towards cotton fibre, but be of lower reactivity towards water that can deactivate it by hydrolysis. The hydrolysis of the dye’s reactive group is similar to its reaction with cellulose fibre but involves a hydroxyl ion in water rather than a cellulosate ion in the fibre. In addition, the dye–fibre bond, once formed, should have adequate stability to withstand repeated washing. Other factors involved are the ease of manufacture, the dye stability during storage and the cost of the final reactive dye.

Reactive groups are of two main types:
(1) Reactive dyes which are reacting with cellulose by nucleophilic substitution of a labile chlorine, fluorine, methyl sulphone or nicotinyl leaving group activated by an adjacent nitrogen atom in a heterocyclic ring.

(2) Reactive dyes those reacting with cellulose by nucleophilic addition to a carbon–carbon double bond, usually activated by an adjacent electron-attracting sulphone group. This type of vinyl sulphone group is usually generated in the dyebath by elimination of sulphate ion from a 2-sulphatoethylsulphone precursor group with alkali.
Although many of the early reactive dyes had only one reactive group in the dyestuff molecule, many of the newer reactive dyes are bifunctional with two or more identical or different reactive groups shows some typical fibre-reactive groups and the commonly used abbreviations for these groups. Dyes with nicotinyltriazine reactive groups (NT) will react with cotton on heating under neutral conditions. 

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Sunday, March 27, 2011

After Treatment And Stripping of Reactive Dye


Washing-off of unfixed reactive dyes after dyeing:
Removal of hydrolysed and un-reacted dye from the goods is a vital step after dyeing. The amount of unfixed dye remaining in a cotton fabric dyed with reactive dyes may have to be less than 0.002% owf.

Both batch and continuous washing process involves three stages.
- Initially, the goods are rinsed in cold and warm water. This is a dilution stage in that removing as much salt and alkali from the goods as possible.
- Secondly, soaping stage much more efficient since at lower electrolyte concentrations the substantivity of the dyes less, making its desorption easier.
- Finally, again a warm rinsing to dilute the final dye solution adhering to the fibres to the point that the amount of unfixed dye carried over to the final drying is minimal. This residual quantity of dye will be deposited on the fibre surface on evaporation of the water during drying and will be easily removed by later washing. Obviously, the amount must be as small as possible.

After-treatment of Remazol dyes:
There are two factors are important during the aftertreatment of Remazol dyeing. The dyeing should not be soaped at the boil under alkaline conditions. This is ensured by neutralizing with acetic acid before soaping. The unfixed (hydrolysed) dye is best removed by boiling with a detergent solution at the boil. It is important to note that the substantivity of the unfixed dye is reduced at higher temperatures and at the boil, the dye has practically no affinity for the fibre and the loosely held dye rapidly diffuse out. If this dye is removed completely, it is not necessary to treat the dyeing with a cationic dye fixing agent to achieve the optimum perspiration and water fastness.

If the boiling after-treatment is carried out under alkaline conditions, some amount of the dye already fixed (reacted with the fibre) is separated by the rupture of the dye - fibre bond, since this bond is not stable to alkali especially at the boil.

When sodium silicate is used as the alkali for fixing the dye, neutralization with acetic acid should not be done. If it is neutralized insoluble silicic acid may get deposited in the fibre producing a harsh feel. In this case, an overflow rinsing with warm water should be given before theboiling after-treatment. (Sodium silicate is more easily washed off than caustic acid). Sodium hexametaphosphate 2 g/l is to be added to the boiling after-treatment bath. 

Stripping of dyed materials:
Partial stripping:
The material is treated in a solution containing 5 to 10 ml glacial acetic acid per 1000 ml. water at 85-95°C until the shade is reduced to the desired extent. In the case of viscose rayon 2.5-10 ml of formic acid (85%) is used in place of acetic acid. The material is then rinsed and soaped at boil for 15 minutes.

Full stripping:
It is difficult to strip fully fixed dyeing completely to a white, but they can be reduced to a form suitable for re-dyeing to dark shades. The material is treated at boil in a solution containing 5 gms of sodium hydrosulphite and 2 gms of soda ash per litre of water for 20 minutes. It is then washed and treated at room temperature in l°Tw sodium hypochlorite, soured, rinsed and soaped at boil for 1 0 - 1 5 minutes.

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