What is a cut-to-length line?
This cut-to-length line, also known as a coil slitting line, drop line or CTL, is designed to unroll and flatten steel coils, which are then cut to the desired width or length and back punched to achieve the final profile.
Line handling with wide coils is typically equipped with quick tool change systems to accommodate different cutting applications, uncoiler and back-flushers systems and collection systems to stack sheet products into bundles. High-performance slitters are used in fixed-length cutting lines, which are typically circular cutters that handle a variety of rolled metal coils and efficiently cut them to precision lengths.
Slit steel manufactured by fixed-length cutting lines is rolled steel that is cut to a specific length by a master coil, also known as a slit-to-width coil.
Typically, a fixed-length cutting line consists of three main components, namely the decoiler, slitter and back-flushers. As the production cycle begins, the rolled coil is fed and flattened through the decoiler system, thereby eliminating defects on the coil surface.
In the next stage, the flattened material is loaded onto a cleat between the circular cutting wheels, which are mounted on the top of the slitting system and the bottom.
The slit-to-width coils are then rewound by the recoil equipment.
To achieve ideal coil slitting and forming, the machinist must determine if the mandrel size, tool kit, tool change system, horsepower, and tensioning device are appropriate for the material and application specifications.
Coil length cutting process
1. Uncoiler
Line handling with wide coils is typically equipped with quick tool change systems to accommodate different cutting applications, uncoiler and back-flushers systems and collection systems to stack sheet products into bundles. High-performance slitters are used in fixed-length cutting lines, which are typically circular cutters that handle a variety of rolled metal coils and efficiently cut them to precision lengths.
Slit steel manufactured by fixed-length cutting lines is rolled steel that is cut to a specific length by a master coil, also known as a slit-to-width coil.
Typically, a fixed-length cutting line consists of three main components, namely the decoiler, slitter and back-flushers. As the production cycle begins, the rolled coil is fed and flattened through the decoiler system, thereby eliminating defects on the coil surface.
In the next stage, the flattened material is loaded onto a cleat between the circular cutting wheels, which are mounted on the top of the slitting system and the bottom.
The slit-to-width coils are then rewound by the recoil equipment.
To achieve ideal coil slitting and forming, the machinist must determine if the mandrel size, tool kit, tool change system, horsepower, and tensioning device are appropriate for the material and application specifications.
Coil length cutting process
1. Uncoiler
The uncoiling process in a decoiler system begins with the automatic feeding of the steel coil or master coil into a double cone or expanded mandrel single end decoiler. The double cone type of the decoiler is more suitable for heavy duty applications, while the multi-purpose mandrel type is an excellent solution for both light and heavy loads.
Rolled coils are fed into the cone via a trolley ramp and quick-load coil carriage. Raw material is loaded into the de-coiler cone by means of a pusher ramp and a quick-load coil cart. The loading cart screws the mandrel into the inner diameter of the main coil material and then rotates it off the cone or mandrel. The material will be stripped to allow the coil head to enter the edge guide smoothly prior to the straightening tool. The flattening operation of the coil is especially important when the flatness of the coil and the absence of defects on the surface of the material are critical in the further coil handling process.
2. Cutting length
2. Cutting length
At this stage, the uncoiled material will be loaded into the slitting system, which consists of two parallel mandrels with knives cutting under rotation. The cutting knives will partially enter the coil, causing cracks or breaks on both sides of the steel. The sheets, cut to length, will then separate from one to the other. Many applications require peel rings to provide a more desirable edge and to eliminate any burrs and defects that may interfere with downstream operations.
After precision cutting, the outer edges of the product have edge trim that needs to be processed by a scrap winder. In some cases, the product being cut is so thin that the machinist can utilize a recirculation pit. This may take up different thicknesses of the slit width coils, especially when the edges are significantly thinner than the center section. The circulation pits mentioned here can also manage additional volume prior to the tensioning stage.
3. Backflush
3. Backflush
Before stacking the sheet products, the slit width coils that need to be recoiled by the expanded core recoiler system are cut into lengthwise lines. The recoiler system can usually be extended with expansion pads or leaves ranging from 60 cm or larger in diameter. Recoiler systems are equipped with arm outer shafts with separating discs that are mounted directly with the circular slitter. This maintains any interlacing for narrow coil applications. Next, the treated sheets are forced off the mandrel onto the coil carriage where they are stacked into bundles by the sheet stacker.
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