Although computerized cutting is widely used in the industry, operator control cutting is still used by most small and mid- sized manufacturers, many large firms use both manual and computerized cutting. Categories of cutting methods are;
I) Fully manual cutting
II) Operator controlled powered knife cutting
I) Fully Manual
1) Hand Shears
Hand shears is the oldest cutting device, are normally used only when cutting single or double plies. Usually it is used in garment’s sample room and custom tailoring purpose. Hand shears required physical strength to cut fabric and accurate cutting to the line can be achieved with practice. The obvious disadvantage of the method lies in the time it consumes and the consequent high labor cost per garment, but it is appropriate for made-to-measure garment.
II.Operator controlled powered knife
Manually operated systems depend on the skill of the cutting operator to position, manipulate, and guide the fabric or cutting device. With the exception of hand shears, most cutting devices have an external power source that controls the speed of the cutting blade, and an operator controls the lateral movement of the cutting device while propelling it into the spread. Operator-controlled cutting equipment may be portable, stationary and auxiliary.
1) Portable cutting knives
Portable knives can be moved to and through a spread by an operator. There are two main types of portable knives: vertical reciprocating straight knives and round knives. Structurally and mechanically, the two types of machines share many similarities.
i. Straight knife
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.
ii. Round knife
Rotary or round knives can be identified by the round blade that cuts with a downward turn at the leading edge. The cutting capacity or spread height is determined by the radius of the blade, motor size, and speed. Because of the flat, round blade, this knife cannot be manipulated around tight curves and sharp angles. This type of knife is used primarily for straight cuts and large radius curves.
2) Stationary Cutter
Stationary cutters are those cutting machines that have blades or cutting devices that remain in a fixed position. Stationary cutters require the operator to position and control fabric blocks in relation to the blade. The two basic types of stationary cutters are band knives and die cutters.
i. Band knives
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. Band knife blades are finer and narrower than reciprocating blades, which makes 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. Templates of plastic or heavy cardboard may be placed on top of a sectioned block to provide a guide for cutting specific shapes. Some manufacturers use band knives instead of die cutters because they are faster and less labor-intensive. Band knives are used to trim precut blocks of small or midsized pieces. They would not be used for cutting a whole spread or large pieces because the operator would be required to maneuver the block around the blade. There are also safety concerns with using an open blade similar to those regarding using a band saw in a wood shop.
ii. 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 pre-shaped 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. 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.
Dies can also be used to cut shapes from the center of a garment part. The accuracy and consistency of die cutting can be affected by irregular surfaces, improper placement of the die, and damaged or dull dies. Die cutting is labor- intensive when dies are manually placed. Die cutting can be automated for continuous line cutting.
Figure: Dye cutting machine
iii. 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 inaccurate 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, which is discussed later in this chapter.
Figure: Servo cutter
Manually operated systems depend on the skill of the cutting operator to position, manipulate, and guide the fabric or cutting device
1) Hand Shears
Hand shears is the oldest cutting device, are normally used only when cutting single or double plies. Usually it is used in garment’s sample room and custom tailoring purpose. Hand shears required physical strength to cut fabric and accurate cutting to the line can be achieved with practice. The obvious disadvantage of the method lies in the time it consumes and the consequent high labor cost per garment, but it is appropriate for made-to-measure garment.
Figure: Hand shears
II.Operator controlled powered knife
Manually operated systems depend on the skill of the cutting operator to position, manipulate, and guide the fabric or cutting device. With the exception of hand shears, most cutting devices have an external power source that controls the speed of the cutting blade, and an operator controls the lateral movement of the cutting device while propelling it into the spread. Operator-controlled cutting equipment may be portable, stationary and auxiliary.
1) Portable cutting knives
Portable knives can be moved to and through a spread by an operator. There are two main types of portable knives: vertical reciprocating straight knives and round knives. Structurally and mechanically, the two types of machines share many similarities.
i. Straight knife
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.
Figure: Straight knife
ii. Round knife
Rotary or round knives can be identified by the round blade that cuts with a downward turn at the leading edge. The cutting capacity or spread height is determined by the radius of the blade, motor size, and speed. Because of the flat, round blade, this knife cannot be manipulated around tight curves and sharp angles. This type of knife is used primarily for straight cuts and large radius curves.
Figure: Round knife
2) Stationary Cutter
Stationary cutters are those cutting machines that have blades or cutting devices that remain in a fixed position. Stationary cutters require the operator to position and control fabric blocks in relation to the blade. The two basic types of stationary cutters are band knives and die cutters.
i. Band knives
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. Band knife blades are finer and narrower than reciprocating blades, which makes 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. Templates of plastic or heavy cardboard may be placed on top of a sectioned block to provide a guide for cutting specific shapes. Some manufacturers use band knives instead of die cutters because they are faster and less labor-intensive. Band knives are used to trim precut blocks of small or midsized pieces. They would not be used for cutting a whole spread or large pieces because the operator would be required to maneuver the block around the blade. There are also safety concerns with using an open blade similar to those regarding using a band saw in a wood shop.
Figure: Band knife
ii. 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 pre-shaped 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. 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.
Dies can also be used to cut shapes from the center of a garment part. The accuracy and consistency of die cutting can be affected by irregular surfaces, improper placement of the die, and damaged or dull dies. Die cutting is labor- intensive when dies are manually placed. Die cutting can be automated for continuous line cutting.
iii. 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 inaccurate 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, which is discussed later in this chapter.
No comments:
Post a Comment