Saturday, May 28, 2011

BATCH DYEING OF WOOL WITH REACTIVE DYES




WOOL DYEING PROCESS WITH REACTIVE DYES
Batch dyeing of wool with reactive dyes is a very popular process. In batch dyeing process reactive dyes are usually applied to wool at pH 5–6 using ammonium salts, and acetic acid as required. At higher pH values, exhaustion is too low, and at lower values rapid dyes uptake gives unlevel dyeings in batch dyeing process. Slightly higher pH values are used for dyeing paler shades (pH 5.5–6.0) and lower values (pH 5.0–5.5) for deep shades in batch dyeing of wool. Fibre Reactive dyes often give quite good exhaustion at temperatures below the boil but the dyeing temperature will eventually be raised to 100 °C to ensure that reaction with the wool is as complete as possible. Some procedures recommend a holding stage at an intermediate temperature of 65–70 °C for 15–20 min to allow the dye to migrate before it reacts with the wool.
Batch dyeing machine for with reactive dyes.
RELATED POST 
REACTIVE DYES FOR WOOL FIBRES - Details about wool dyeing,

Because of their tendency to give unlevel, skittery dyeings, reactive dyes are usually applied to wool in the presence of proprietary levelling agents in case of batch dyeing process of wool. These are often amphoteric, having both cationic and anionic groups in the molecule. In contrast to most levelling agents, which decrease the dyeing rate, the auxiliary products for dyeing wool with reactive dyes accelerate dyeing. The anionic dye complexes with the cationic site in the auxiliary product but the remaining anionic site provide substantivity for the wool surface. The bulky dye–auxiliary complex exhausts well onto the fibre surface at relatively low temperature, better than the dye alone, but cannot penetrate into the fibres. The complex breaks down as the dyeing temperature increases so that the smaller liberated dye molecules can then absorb into the wool. The use of such products avoids unlevel, skittery dyeings and provides better compatibility of dye mixtures during the batch dyeing.

Deeply dyed wool fibre or fabric with reactive dyes in batch dyeing process must be aftertreated to remove unfixed dye so as to give the best wet fastness. This is particularly important to ensure that there is no staining of adjacent undyed material during washing. After dyeing of wool with reactive dye, the material can be washed at 80 °C for about 15 min using a dilute ammonia solution at pH 8.0–8.5, and then rinsed in water with a little acetic acid. To avoid any alkali damage to the wool after batch dyeing, washing can be done with hexamine (hexamethylenetetramine from formaldehyde and ammonia) at pH 6.5, or with sodium bicarbonate. Certain proprietary chemicals can be added to the dyebath on completion of dyeing and their hydrolysis increases the bath pH to around 7. For example, hydrolysis of sodium trichloroacetate gives chloroform, carbon dioxide, both of which are volatile, and sodium hydroxide (Scheme 16.6). The actual colour removed may consist of unreacted dye, hydrolysed dye and products of the reaction of the dye with soluble wool hydrolysis products such as ammonia and hydrogen sulphide or amino acids.

Reaction related to dyeing wool with reactive dyes:
CCl3 CO2Na + H2O = HCCl3 + CO2 +NaOH

Shrink-proof wool, which has been treated with resins in the Hercosett process, remains cationic on the surface and gives rapid uptake of reactive dyes. The usual auxiliary levelling agents may be less effective in this case. The deposited resin protects the wool from damage and the best fastness results for deep shades are obtained by dyeing at 110 °C for 30 min.

Wool dyed in deep shades with reactive dyes is better protected from damage during dyeing. A number of explanations for this have been proposed. These involve protein chain crosslinking, reaction with thiol groups that interferes with 357 the reformation of disulphide links, and reaction with non-keratinous proteins in the cell membrane complex and endocuticle. So reactive dye is best for dyeing wool fibre in batch dyeing process but proper care should be taken other wise shade will be uneven.

RELATED POST

Vinyl sulphone dyes or Remazol dyes are good quality Reactive dyes 

After Treatment And Stripping of Reactive Dye

Structural discussion of reactive dyes those suitable for cotton fibre

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

 

Friday, May 27, 2011

GARMENTS MATERIALS HANDLING




Materials handling is concerned with the efficient movement of goods through the conversion process. From the time fabric is unloaded from the truck until finished garments are packaged and shipped, storage and movement of materials and work in process must be planned and tracked to facilitate throughput. Handling materials does not add value to a product, but it affects work flow and productivity.

Handling costs can be reduced by eliminating as much handling as possible and reducing the distance materials are moved. Three aspects of materials handling need to be planned and evaluated: (1) handling and processing of in coming goods, (2) movement of work in process, and (3) distribution of the finished product.

Materials handling methods used at work stations depend on how garment parts are presented to the operator, the degree of automation, and the disposal system used. Materials handling procedures are incorporated in the production method for each operation. Work aids such as slanted tables for positioning parts, folders and binders for positioning trims, and automated cutters are some of the many ways an operation may be simplified and handling kept to a minimum. Handling time may account for up to 80 percent of sewing operation time.

Thursday, May 26, 2011

Marketing of Man-Made Fibers

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Man-made fibres Market analysis:
Man-made fibres are marketed as commodities, as brand name fibers or as controlled brand name fibers. Fibers marketed as commodities are used without identification of source and are sold to any buyer in the open market. A dress labeled 100% Polyester has been made with commodity polyester fibers. Brand name man made fibers are identified by source through the brand names used. The fiber producer spends much Promotion money to establish his brand name and expects manufacturers, wholesalers and retailers down the line to take advantages of it. The man made fiber producer, however, frequently does not have complete control over the use of his brand name after the mill buys the finer. It is possible that a quality fabric could be used to make a poorly constructed garment and that this article would carry the fiber brand name on a label or hang tag. He controlled brand name approach enables the fiber maker to rigidly control the selling and subsequent use of the fiber.

Relationships are established with specific textile mills and fabric users who will utilize the fiber properly. A quality control program by the fiber producer insures that only products, which have satisfactorily passed various tests related to the end use, are allowed to use the fiber brand name. Unfortunately, consumer is usually unable to distinguish between a controlled brand name fiber and an uncontrolled brand name fiber.

Most of the fiber companies will sell their regular type fibers as a commodity as well as with a brand name. Under a licensed brand name or trademark program, the licensing company allows its brand name or trademark to be used by other companies in return for a specified remuneration.
In some cause, the product made by the licensee is carefully checked for quality by the licensor, but in other cases, it is not.

Man-made fiber producers license their Fiber brand names to certain mills that buy their fibers. The fiber brand name hangtags are later attached, for examples, to garments or draperies made from the licensed mill’s fabric. The fiber producer is compensated by receiving a slightly higher price from the mills than if the fibers were sold unbranded.

A licensed controlled brand name or trademark program means that the product also has satisfactorily passed various tests related to its end use before the brand name can be used. The tests are specified by the licensor. Such a program requires the maintenance of a quality control program to insure that the comp anises to which the trademarks or brand names have been licensed are making products that meet certain levels of quality.

In this way, the licensor can best attempt to insure that the brand name or trademark will not lose its value. Unfortunately, the levels or quality are not the same for each program and the consumer frequently does not know which controlled brand names indicate the best quality products.

The licensed controlled brand name programs of the textile industry became important in the early 1930’s when Cluett, Peabody & Company started to license their fabric shrinkage processes using the name Sanforired and Joseph Bancroft and Sons started to license their Everglaze Process, which insured fabric luster. In the 1960’s, the Celanese Corporations became the first major proponent among fiber producers of the licensed controlled brandname programs. Fabrics, as will as garments and other articles containing its branded fibers, had to pass specified quality tests before a Celanese hang tag would be placed on t he item. The program is still continuing.

The following are some of the textile licensed controlled brand name or trademark programs presently in use to market of man made fibre:

A. Polyextra ® textured polyester yarn program for upholstery fabrics—BASF Corporation.
B. Sanforized ® program for shrinkage control of woven fabrics and Sanforized Plus- 2 ® which is durable press program – Cluett, Peabody & Company;
C. Trevira ® polyester program for fabric quality – Hoechst Celanese Corporation;
D. Zepel ® program for fabric water and stain repellency quality
E. I. Du Pont de Nemours & Company. Inc.

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FABRIC RESOURCES



Primary Sources of Fabric
A primary source of fabric is a company that makes or creates the material. The Firms in this category are mills and mills and converters. Some of the mills produce woven fabrics exclusively; others make only knit fabrics, while some of the giant mills manufacture both.

In the Primary fabric market, most sales are based on contracts with shipments to be made months later. The converters and mills work closely with their customers designer’s and merchandisers to create designs and working samples. Sales of fabric either in inventory or about to be ready for sale (called spot or nearby goods) also occur, but on a much smaller scale. Unusually, very small orders will not be take, this being the function of the jobber.



 Fabric Resources (Mill)
The mill is a company that owns textiles machinery and makes fabric. The large textile mills are vertically integrated. They not only make the fabric, but also produce their own yarn and perform the finishing processes required after the fabric has been completed. However, they do not make their own fibers.
The mills sell their finished fibroin to various customers. The converter, discussed in the next section, is a major buyer.

Garment and home furnishings manufacturers use fabrics in making their products. Jobbers, who help dispose of excess or surplus merchandise for the mill, are another customer. Large retail stores, which in turn sell to the home sewer, also buy from the mills. Most of the staple fabrics are sold by the mills. A staple fabric is one, which is produced continuously each year with no change in construction or finish, and includes poplin, taffeta, tricot and sheeting. There are, however, many fancy or novelty fabrics also offered for sale by the mills.

The converter is an individual or organization that buys greige (or grey) goods (unfinished fabric), usually from mills, has the fabric dyed or printed and finished buy other companies, and then sells the finished fabric. All aspects of the fabric, including construction, design color and finish, are determined by ther converter.

Fabric Resources (Importer)

Many textile fabrics (and yarns) are made overseas and then imported into the United States. Since about 1980 the volume of textile imports has risen dramatically and today accounts for a large percent of the fabrics used domestically. While the greatest amount of textiles and textile products comes from the Far East. They are also received from many other parts of the world.

The textile importing companies are of two types. The direct importer buys fabrics or manufactured textile products (e.g.., clothing or soft luggage) from a foreign mill or other supplier. The other type, the import mills, is a foreign company that owns textile machinery and makes the fabric (or yarns) that is then exported. A secondary source of fabric is a company, which buys cloth and then sells it. Such a company is not involved in the making or creating of the material. Therefore, any seller of fabric other than mills and converters is considered a secondary source.

Fabric Resources (Jobber)
The jobber buys from mills, converters and garment manufacturers and other users. Although their purchases of a specific fabric type. Print or color are usually relatively small, jobbers nevertheless are valuable customers of the mills and converters. Jobbers often buy mill or converter fabrics that would otherwise be difficult to sell, including discontinued styles and colors and mill overruns. ( A mill overrun or tailing occurs when a mill produces more dyed, printed or finished fabric than the order specified . An overrun occurs for various reasons, including allowances for damaged yardage and short pieces unacceptable to the customer.) The jobber also sometimes buys fabric from users who have excess cloth. The excess cloth usually results from a decline in anticipated sales.

Fabric Resources (Retail Store)

Fabrics sold in the retails store are called over the counter sales and are bought by home sewer for their own needs. Put-up is the tern used to indicate the way fabric is packaged when it is sold. Most fabrics sold to garment and other manufactures are in a rolled, in either open width or tubular form. Some fabrics are doubled and rolled. Such fabrics are folded in half lengthwise, and then wound around a flat piece of cardboard. Cloth when sold to retail stores is usually in this put-up, in under 30 yard lengths. Velvet and other plush fabrics are usually not rolled because.

The resulting pressure would flatten the surface. The fabric is placed on a frame so the surface3 doses not contact any other part of the cloth. Pieces of woven fabric less then 40 yards in length are called shorts. These pieces are usually sold in either 20 to 40 yard pieces ( called 20 ‘ to 40 ‘s ), 10 to 20 yard pieces ( called 10 ‘s to 20’s ) or 5 to 10 yard pieces (Called 5’s to 10’s). Jobbers normally are the buyers of these short pieces of woven fabric.

Pound goods are usually very short pieces of fabric (often containing pieces less than one yard in length). They are sold by the pound and not by the yard. Fabric that cannot be sold in nay other manner is sold this way. These goods are bought at the buyer’s risk and receive the lowest price. End cases include stuffing for furniture and clothes for dolls.


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GARMENTS SPREADING AND SPREADING EQUIPMENT



Objectives of garments spreading:
 -Garments Spreading equipments and surfaces
 -Examine the role of fabric control devices of garments spreading.

Basic garments spreading equipment consists of:
(i) Spreading surfaces,
(ii) Spreading machines,
(iii) Fabric control devices during spreading, and
(iv) Fabric cutting devices.

Many firms operate productively with manually operated equipment, while other firms find the automated, high-tech equipment to be cost-effective for their operations. Under-standing the parts and complexities of spreading equipment provides insight for troubleshooting problems and better preparation for the process.
Spreading Surfaces:
The appropriate type of spreading surface is determined by the fabric type, spreading equipment, cutting method, cutting equipment, and the firm's quality standards. Spreading requires a flat, smooth surface. If the spreading surface doubles as a cutting surface, it also must be level. Spreading and cutting may be done on the same surface, but automated cutting often requires spreading and cutting to be done in adjacent but separate locations.

Spreading and cutting surfaces are available in standard widths that correspond to fabric width. Narrow fabric can be spread on a wider table. A spreading surface needs to be about 10 inches wider than the fabric. Spreading tables may have tracks or rails placed along one or both sides of a tabletop or just a few inches off the floor. This track helps guide and control the spreader as it moves up and down the length of the table. With some types of equipment, the table tracks are geared to synchronize the movement of the spreading machine with fabric unrolling, in order to regulate tension.

Spreading tables may also be very specialized for certain types of fabric and cutting equipment. Pin tables have rows of pins located below the surface that can be extended through slats to hold fabric in a precise location for accurate matching of pattern repeats. Vacuum tables are used to compress lay-up and prevent shifting or movement during cutting. A spread is covered with a plastic film that forms a seal over the lay-up when a vacuum is applied. A lay-up of quilted fabric can be compressed as much as 75 percent when the vacuum is used. This allows more plies in the lay-up and restricts the movement of slippery fabrics for more accurate cutting.

Cutting equipment may be moved to a lay-up as another lay-up is prepared further down the table, or fabric can be spread on one surface and then transferred to the cutting surface. Air flotation tables, when activated, allow easy movement of a lay-up onto an adjacent cutting area. A layer of air between the table surface and the bottom layer of paper reduces friction and allows a lay-up to be moved easily without putting stress on the fabric or the operators.
Spreading tables with conveyorized surfaces carry the fabric to the cutting machine so that no time is wasted. Ideally one lay-up can be cut while is being spread. Conveyors may be used with computerized cutting systems, large die presses, and laser cutters.

Garments Spreading Machines:

Automatic Spreading Machine with fabric control devices
The fundamental purpose of spreading machines is to superimpose layers of fabric in a smooth, tension-free manner for accurate and efficient cutting. Manually operated spreading machines can be as simple a roll bar mounted on four wheels that is pushed up and down a spreading table by an operator. Manual spreaders travel only as fast as an operator moves them, while some of the faster automated machines can spread 100-150 yards per minute. Spreading speed can only be utilized on long spreads with few defects. Spreading speed may affect productivity, quality, and cost of the operation, but it should not be the primary focus for purchase of new equipment. Manual spreading machines may be used by small firms as the primary spreading device and by large firms for short spreads. As spreading machines become more sophisticated, they are motor driven and have fabric control devices included increasing productivity, decreasing variability, and making spreading more cost-efficient.

Fabric Control Devices during garments spreading:
Fabric control devices are mechanisms that control fabric as it is carried up and down the table and unrolled by the spreading machine. These devices include:
(i) Tensioning mechanisms,
(ii) Positioning devices, and
(iii) End treatment systems.
(i) Tensioning involves synchronizing the rate of spreading with the rate fabric is unrolled. A positive feed system utilizes a covered roller that is driven and timed to the movement of the machine. It prevents the momentum of a large roll from continuing to unwind when the machine slows down or stops. Roller covers of different materials may be used to give better gripping power for different types and weights of fabric.

(ii) Positioning devices and sensors monitor position and control fabric placement during spreading. These devices improve the quality of a spread. Electronic edge sensors monitor selvages as fabric is spread. A deviation from the proposed alignment triggers a motor that shifts the roll to the correct position. Alignment can be held to one-eighth inch tolerance with these devices.

(iii) Width indicators may sound an alarm to alert the operator whenever fabric becomes narrower than the established width. Width variations are analyzed to determine where in the marker they fall, whether the fabric will still fit the marker, or whether the variation should be treated as a defect and removed.

(iv) End treatment devices are used with spreaders but are separate and placed at the end of the spread. The specific end treatment equipment needed depends on whether the spreading mode is face-to-face or face-one-way. A face-to-face spread utilizes an end catcher and folding blade that work together. These are mechanical parts, mounted at opposite ends of the marker to catch and hold the fabric as the blade shapes and creases the fold. An overfeed device may be built into the spreading unit, which automatically feeds extra material when a fold is to be made. End treatments have a major impact on fabric waste. There must be enough fabric at the end of a lay to retain it in place, but any fabric beyond the end of the marker is wasted.

For F/O/W spreads, a knife box is needed along with an end catcher. A knife box contains a cutting unit (usually a small rotary knife) that operates in a track and cuts across the fabric width when engaged. With face-one-way spreads, each ply must be cut from the roll at the end of the marker. The catcher simply holds the fabric end in place for cutting. As multiple plies are spread, the fold blade and/or knife box must be elevated to the height of the top ply in order to fold or cut the fabric.

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Wednesday, May 25, 2011

FABRIC DICTIONARY (E-BOOK FOR FREE DOWNLOAD)



Textile fabric dictionary or glossary of fabric terms and definitions is an important free e-book for textile engineering, fashion design or apparel merchandising students. I try to provide important textile terms and definitions on knitted, woven and non-woven fabric in this free e-book.

This Complete Textile Fabric Glossary is intended to be a convenient reference for textile terminology. Although it covers all types of textile terms broadly, its special emphasis is on manufactured fibers - what they are, how they are produced, and how they are used.

The first edition of this textile fabric dictionary was published as a book by Md Tariqul Alom Ansari in Bangladeshi market. The author is my friend. By taking his permission, I try to publish his TEXTILE FABRIC DICTIONARY book in my blog as an e-book. With in short days, I am going to publish the full edition of this book named by “TEXTILE FABRIC DICTIONARY; GLOSSARY OF TEXTILE FABRIC TERMS AND DEFINITIONS”. It must be pdf file formatted free e-book.
Let see the Fabric dictionary:


THE LOCKSTITCH MACHINE; GARMENTS SEWING MACHINE USED MOST OF THE APPAREL FACTORY


Lockstitch sewing machine is very popular sewing machine and widely used in most of the conventional modern garments sewing system. The lockstitch machine is very easy to use but required more power to operate.



Principal feature and sewing elements of a flat-bed lockstitch sewing machine

The three-thread overlock sewing machine


Objectives of lockstitch sewing machine:
-Explain mechanization and automation relative to general- and special-purpose machines
-Examine the basic components of sewing machines and work aids
-Discuss the effect of equipment on product quality andperformance

Modern mass-production sewing requirements have resulted in many variations of the basic flat-bed lockstitch sewing machine. As we have seen, many of these developments are concerned with the form of the bed on which the material to be sewn rests. Cylinder-beds, post-beds, raised- and feed-off-the-arm beds have given rise to machines which differ greatly in appearance, although the actual stitch forming elements contained in these machines remain basically the same. These mechanisms may be grouped under one or other of the two main headings, Rotary hook or Oscillating Shuttle.

The principal features and sewing elements of a modern flat-bed lockstitch machine of the rotary hook type are as illustrated in the figure given below:

STATIONARY CUTTERS FOR FABRIC LAY CUTTING IN GARMENTS FACTORY




Stationary cutter of fabric cutting is important device of garments factory. Stationary cutter means the cutter is fixed and the spreading table is movable. This cutting system is time consuming and costly too. High power supply system is required for this cutting system.

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

Stationary cutters are those cutting machines that have blades or cutting devices that remain in a fixed position. The two basic types of stationary cutters are (i) band knives and (ii) die cutters. Operators must move the fabric or lay up to the machine and engage the cutting action.

BAND KNIVES:
The band knife cutting machine contains a narrow, sharpened, endless steel band moving vertically through the layers of fabric. The fabric layers are guided by hand against the blade. An air cushion will often be provided below the fabric layers to make it easier to guide the material. The plies may be stapled together to prevent slippage. Band knives are used for precision cutting to a depth of up to 300mm. Corners, tight curves and pointed incisions are cut precisely.

Band knives have fine blades that rotate through a slot in the cutting table while cutting. The operator positions, controls, and guides the fabric block around the knife. A band knife can be used to make only lateral cuts into a spread, as the operator must propel the fabric into the rotating blade. Band knives blades are finer and narrower than reciprocating blades, which make it easier to manipulate tight curves and intricate patterns. Band knives are more accurate than vertical knives when used to cut small blocks or shave small amounts off precut blocks. Band knives are used to trim precut blocks of small or mid size pieces. They would not be used for cutting a whole spread or large pieces because of having to maneuver the block around the blade.

DIE CUTTING:
Die cutting is the most accurate means of cutting because each and every piece is cut to the exact same shape. Dies are reshaped metal outlines with one cutting edge. Die cutting involves use of a die to cut out a specific garment part or trim from a single piece or small block of fabric. The die-cutting operation involves placement of the fabric, positioning the die on the fabric, and engaging the machine to press the die into the fabric.

A die cutting machine is provided with prefabricated cutting tools, (cutting dies) having the exact shape of the garment pieces. Die cutters are used mainly for leather, coated and laminated materials and in areas where the same patterns are used over a long period, e.g., production of working clothes. The dies are expensive to make. Dies are frequently used to cut small pieces that require high accuracy, such as collars, pocket flaps, and appliqu├ęs. Leather goods are frequently die cut. Gloves with their fine detail are usually die cut as are shoes that require consistency of parts.

SERVO CUTTERS:
The bridge between computer-controlled and manual cutting is the servo-cutting system. This type of system has an overhead servo motor with adjustable speed and a suspension system that supports the knife perpendicular to the cutting table. This reduces problems with tilting the blade and in accurate cutting. The knife is mounted on a swivel arm, which is extended above the cutting table. It also has a small base plate and narrow blade guide for easier maneuvering by the operator. It can make tighter turns with less distortion in the lay. It combines vertical cutting and band knife cutting into one machine. This type of system enables the operator to cut deeper spreads with greater accuracy than with a freestanding straight knife and for a lesser investment than computerized cutting.

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DIMENSIONS & TYPES OF MARKERS; SPLICING


 DIMENSIONS  AND TYPES OF MARKERS; SPLICING

Objectives:
 -Examine how material utilization is impacted by dimensions of markers
 -Understanding different techniques of marker making for specific order quantities
DIMENSIONS ; TYPES OF MARKERS; SPLICING

Markers are made to fit specific widths of fabric and quantities of sizes. If a marker is narrower than the fabric, the unused fabric is wasted. If a marker is wider than the specified fabric, garment parts located on the edge of the marker will not be complete. Fabric is purchased by width but often it runs wider than the required width. When fabric width is grossly inconsistent, fabrics in a lot may be grouped by width and different markers produced for each width. Using the extra width in planning markers can save significant yardage.
Markers may be produced in sections or blocks or be continuous. Blocked or Sectioned Markers contain all of the pattern pieces for one style in one or two sizes. Sections may be used separately or joined together to form an extended multisize marker. Blocked or sectioned markers are easier to visualize and handle, but they may not produce the best utilization of fabric.

Sectioned markers may be used to adjust the volume requirements for various sizes or as a remnant marker. High-volume blocks can be placed on one end of the marker and low-volume blocks placed at the other end so the fabric can be spread to correspond with the volume needed for each block. Blocking keeps garment parts for one size in close proximity, which facilitates bundling and handling. Sectioned markers are advantageous if there is an en-to-end shade variation of the fabric. The following picture shows a spread that could be used with a sectioned marker and an unequal distribution of sizes.

A stepped spread for a sectioned marker may consist of plies of varied length, spread at different heights. The most frequently used configuration for a stepped spread consists of a group of plies that are spread the full length of the marker and another group of plies beginning at the section line. Stepped spreads are used to adjust the quantity of piece goods to the number of garments to be cut from each section of the marker

Continuous markers contain all the pattern pieces for the all sizes included in a single cutting. They may be lengthy and often require more juggling of pattern pieces. Pattern pieces are grouped by size and shape of the pieces rather than by garment size. Continuous markers often have better utilization because there is more flexibility in grouping and maneuvering large pieces and small pieces. Splice marks are planned into continuous markers to avoid excessive fabric waste and incomplete pieces.

Splice marks are points in a marker where fabrics can be cut and the next piece overlapped to maintain a continuous spread. Splice marks may be one inch or several inches depending on the overlap needed to accommodate the pattern pieces in the area of the splice. The rectangular box indicates the amount of overlap needed. The lower ply should be cut at the end of the box and the new ply of fabric should be aligned with the beginning of the box. If fabric needs to be cut before there is a splice mark, the cut should be made at the last splice mark and the extra fabric used for recuts or smaller markers. Splice marks are inherent when markers are planned in blocks. Piece goods may be spliced at any point where the sections of a marker are joined together. Splices are needed when flaws are removed, a roll change is made, or a short length of fabric is used.

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MARKER PLANNING & MARKER MAKING FOR PARTICULAR GARMENTS.






Objectives of marker planning and marker making:
 -Optimizing fabric utilization through marker making 
 -Understanding the importance of the same in apparel and garments manufacture
Garments manufacturing is very important part of textile production and proper marker planning and marker making is the heart of garments manufacturing. The results of cut order planning are cutting orders that direct marker planning and lay planning. Optimum use of textile material and cutting systems are important considerations in planning cutting orders as more firms incorporate new technology. The purpose of marker planning is to determine the most efficient combination of sizes and shades for each order and to produce the best fabric yield and equipment utilization. One garments cutting order may require several markers to achieve optimum efficiency of marker. Usually one of these is a remnant marker for the short pieces and ends of rolls left over. This helps to reduce fabric waste. Each marker requires a lay of fabric.

A marker is a diagram of a precise arrangement of pattern pieces for a specific style and the sizes to be cut from a single spread. Marker making is the process of determining the most efficient layout of pattern pieces for a specified style, fabric, and distribution of sizes. The process of arranging Pattern pieces in the most efficient manner requires time, skill, and concentration. Markers may be made by manually tracing master patterns onto fabric or paper or by manipulating and plotting computerized pattern images.

THERE ARE TWO TYPES OF MARKER MAKING:
1.Manual marker making
2.Computerized marker making.

1. Manual marker making: Manually produced markers may be created by arranging full pattern pieces on marker paper or directly on the top ply of fabric in a spread. Pattern pieces are traced using a pencil or tailor's chalk. Manual methods of marker planning and making are time-consuming and require a great deal of space. Full-size pieces must be manipulated, adjusted, and readjusted on normal fabric widths. Manually made markers are also subject to errors and inconsistencies that may occur in grain variations, poor line definition, placement and alignment of pieces, and omission of pieces. Accuracy of a manually made marker depends on the skill of the individual who laid out the marker and traced it.

2. Computerized marker making: Computerized marker making is more accurate and provides the greatest opportunity for pattern manipulation, marker efficiency, reuse of previously made markers, and shortest response time. Production patterns may be developed on the computer and/or digitized or scanned into the computer. In addition, parameters for markers are entered into the computer from cutting orders. These might include style numbers, size distribution, and fabric width. Technicians manipulate pattern images on computer screens and experiment with various configurations to determine the best fabric utilization for the marker.

Plotting is the process of drawing or printing pattern pieces or markers on paper so they can be reviewed or cut. Computer-driven plotters may draw pattern pieces, graded nests of patterns, and/or markers with complete annotation, depending on the needs of the apparel firm. New multihead jet plotters are much faster and can print variable line density and width, text identification information, and bar codes. Some garment manufacturers have devices to copy original markers when multiple copies are needed. Plotting is often the bottleneck in the preproduction processes, especially if a firm runs a lot of copies. Many firms run their plotters 24 hours a day to keep up with demand. Firms using computerized cutters may not need paper markers to guide the cutting process and therefore may only print identification information for bundles.
Cut order planning determines how many markers are needed, how many of each size should be in each marker, and the number of ply that will be cut with each marker. Size distribution in a marker depends on the volume of orders for specific sizes, fabric width, how the pieces fit together, and the firm's standard practices for marker making. An efficient size ratio is often 1:2:2:1. For example, an order for one marker may contain one small, two medium, two large and one extra large. Additional markers may include only medium and large, depending on the assortments in the line plan or orders from merchandise buyers. Cutting orders may require making new markers, copying previously made markers, or modifying previous markers.

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MARKER MODES



Marker could be described by the form of the fabric and whether it is symmetrical and/or directional determine the appropriate type of marker for a style. Markers may be open or closed depending on the form that the fabric is presented for cutting. Rolled fabrics are open and flat when spread. Markers for this type of spread require pattern pieces for each part to be cut. Markers made with full-pattern pieces for each part to be cut. Markers made with full-pattern pieces are called open markers. Tubular knit fabrics are closed on both edges and therefore require pattern pieces that utilize the folds. Markers with half-pattern pieces for laying along the folds of the tube are called closed markers. Garment parts must be symmetrical if half-pattern pieces are used.

Objectives of marker modes:
 -Understanding the impact of fabric nap on marker planning
 -Examine the role of symmetry and directionality of fabric

Marker makers must also consider the symmetry (side-to-side) and directionality (end-to-end) differences in fabrics. Symmetric fabrics are the same side-to-side. Asymmetric fabrics such as border prints are different side-to-side. Non-directional fabrics are the same end-to-end. Directional fabrics are different end-to-end. Examples of directional fabrics include knits, n fabrics, and prints with flowers all growing in one direction.
The marker mode is determined by the symmetry and directionality of fabric. There are three types of marker modes: nap-either-way (N/E/W), nap-one-way (N/O/W), and nap-up-and-down (N/U/D). In this case, the term nap is " to indicate the fabric is directional - it is different end-to-end. The nap of a fabric is created by its structure (corduroy or an unbalanced plaid), a finish, or a directional print. With symmetric, nondirectional fabrics, pattern pieces can be placed on a marker with only consideration for grain line. This marker mode is called nap-either-way (N/E/W). Pieces are placed for best fabric utilization.

On some directional fabrics, such as corduroy, it may be possible for all the pattern pieces of one size to be placed in one direction and another size placed ill the opposite direction. This is called nap-up-and-down (N/U/D). With this type of marker, the nap of corduroy jeans may run down for a size 7 and up for a size 9. The critical factor is that the nap must run the same direction in all the pieces of one garment. Napped fabric such as corduroy will appear shaded if the pieces in one garment have the nap running in different directions. Generally N/U/D will yield a better utilization of fabric than N/O/W.
A marker is made for a specific style, fabric, and number of sizes. The length of the marker determines the length of the lay that will be spread. Completed markers are sent to the cutting room electronically or in hard copy for the spreading and cutting processes.

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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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