Garments manufacturing process :: Fabric cutting section


CUTTING
To fabric cut out pattern pieces of garment components as per exact dimension of the patterns from a fabric lay is called fabric cutting. It is totally different from general cutting in which exact dimension is not taken into account. The term fabric cutting is only applicable for garments manufacturing technology.
REQUIREMENTS FOR FABRIC CUTTING
The following points must be fulfilled in fabric cutting:
  1. Precision of fabric cutting: Fabric cutting should be done accurately as per exact dimension of the pattern pieces in the marker. Accurate cutting depends on methods of cutting and marker planning. If manual cutting method is used, then cutting accuracy depends on sharpness of knife, skill of operator, and attentiveness of operator. Computer controlled cutting and die cutting have their self cutting accuracy.
  2. Consistent cutting: Whatever be the cutting method used for fabric lay cutting, it should be ensured that the shape of the cut components from top to bottom lay are of exact size and shape, otherwise the garments produced will be defective.
  3. Infused edge:
    line-height: 115%;">During fabric cutting, the friction between the fabric and the blade produces temperature in the blade; the temperature may be up to 3000C. If the fabric contains synthetic fibres e.g. nylon, polyester, acrylic or their blends, then fused edge may result in the fabric. As because most of those fibres melt at around 2500C. Therefore, sticking of cut edge of fabric will increase the fabric wastage. Moreover, the fused edge after cooling will form hard bid, which will be a problem of irritation during use of garments. To avoid the problem of fused edge formation, the following steps may be taken:
    1.  Reduce the height of the lay;
    2.  Reduce the cutting speed;
    3.  Use anti-fusion paper in the lay at regular interval;
    4.  Lubricate the knife during cutting.




  • Supporting of the lay:  Surface of the cutting table depends on methods of fabric cutting. The table surface should be capable to support the lay as well as to ensure that all the plies are cut at a time during fabric cutting
    •  
    METHODS OF FABRIC CUTTING
    Fabric cutting methods are as follows:
    Manual Method:
    >  Scissor;
    >  Round knife;
    >  Band knife;
    >  Straight knife;
    >  Die cutting;
    >  Notcher, and
    >  Drill.
    Computerized Method:
    •   Straight Knife cutting
    •   Water jet cutting
    •   Laser beam cutting, and
    •  Plasma torch cutting.
    SCISSOR
    It is the oldest type of instrument used for cutting paper, thread, fabric, etc. It is generally used for cutting single layer of fabric but for cutting multilayer of fabrics another type of instrument will have to be chosen. Hence for domestic and tailoring purposes scissor is used extensively but in the ready made garments factory it is used very rarely. Scissors may be left handed or right handed and the cheapest cutting instrument.
               
    ROUND KNIFE
    The cutting knife is a circular disc type component which has a very sharp edge. It rotates at about 1000 to 3000 rpm by electric power
    The main components are circular knife, base plate, motor, knife guard, etc. The sharp edge may be waved, toothed, and plain. Diameter of blade varies from 6 to 30 cm. Cutting power of circular knife is ten times higher than straight knife for same rpm of knife.
    There are some problems with the round knife machine that limit its application in the RMG sector:
    •   Cutting depth up to 40% of the blade diameter;
    •     Cutting is not done at 90% angle (like straight knife), hence it is difficult to cut out pattern  pieces directly from the fabric lay.
    •     Not suitable for cutting small components from the fabric lay.
    •     Mainly used for cutting out block of fabric from the lay.
    STRAIGHT KNIFE
    It is the commonest and extensively used fabric cutting machine in the garments manufacturing Industries.The machine has a base plate; under base plate there are wheels to facilitate easy movement of the cutting machine during fabric cutting on the cutting table. There is a big motor on the stand; the stand is connected to the base plate. On the motor, there is a handle to move the cutting machine. The blade or knife is situated inside of the stand. 
     
    The knife has a knife guard. There is a grinding wheel near to the knife which facilitates knife sharpening during fabric cutting. Two types of power are needed to cut fabric in this machine. Electric power is used by the motor for the reciprocating movement of the knife and manual power is needed to move the cutting machine and blade through the fabric lay.
    Higher the size of the motor, higher the force of the blade and higher the depth of the fabric lay could be cut. The height of the blade may vary from 10 to 30 cm and stroke of blade may be 2.5 to 4.5 cm.
    The cutting edge of the blade may be plain (for soft fabric), waved (for plastic), saw edge (for canvas), and serrated (for hard fabric e.g. denim). For cutting different types of fabric, different speeds of blade may be set. There are modified versions of straight knife also available. The modified version has a cantilever type arm which supports the motor and entire weight of the machine. The cantilever arm is supported by a stand. The stand is moveable along the entire length of the cutting table.
    Advantages:
    •    As it is comparatively cheaper, easy moveable and maximum lay height could be cut, used extensively in garment industries.
    •    Could cut fabric at more curved line than the round knife.
    •    Cutting could be done for up to 10 inch depth of the lay.
    •    Quick fabric cutting.
    •    Components could be cut out directly from the fabric lay.
    •    Grinding could be done during cutting.
    •    Could be cut at any angle.
    Disadvantages:
    •    Knife deflection may result due to heavy weight of the motor.
    •    Higher the depth of the lay, higher will be the deflection.
    •    Possibility of accident is higher.
    BAND KNIFE
    It looks like a saw mill wood cutting machine but of smaller in size. An endless blade is placed on three pulleys and the blade is driven by a motor continuously in one direction. The blade passes through a slot of the cutting table. The operator places the fabric lay onto the table, pushes the block of fabric towards the rotating blade and cuts the pattern by moving the lay. To ensure accurate cutting, templates are use
    Advantages:
       Very accurate cutting can be achieved;
       Suitable for smaller components cutting;
       Cutting at any angle could be done easily.
       Use of templates facilitate accurate and consistent cutting.
       Possibility of accident is lower.
    Disadvantages:
       Fabric wastage is higher due to use of fabric block;
       Work load is higher;
       Not suitable for larger sized components cutting.
    DIE CUTTING
    The main components of a die cutting machine are ram head, die, cutting blade, motor, etc. The die is made from steel strip, as per exact size and shape of each pattern. One end of the steel strip is sharpened and the other end is secured by tie bar. The die is placed onto the fabric lay and pressure is applied on the die by ram head. As a result, they cut the fabric by embedding into the fabric lay.
    Advantages:
       Suitable for smaller sized components cutting;
       Cutting could be done at any angle;
       Lower cutting time;
       Suitable for cutting knit fabric.
    Disadvantages:
       Fabric wastage is higher;
       High labor cost;
       Not suitable for quick style change;
       Not suitable for larger size components cutting.
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