Thursday, May 26, 2011

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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Wish you good luck......................................................

1 comment:

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