Wednesday, May 25, 2011

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 appliqués. 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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