FOCUS ON COIL PROCESSING
Image: Shutterstock. com.
Two take-up reels in the space-saving design of a zinc slitting line from Burghardt + Schmidt GmbH for Grillo-Werke.
Corrective levelling is configured like a basic steel coil leveller. However, the backups are fully adjustable to create bend in the rolls. A corrective leveller can reduce shape defects across the strip and remove the entire coil set. These levellers have adjustable backups. Some may have a 5HI or 6HI configuration for surface-critical material, such as painted or stainless steel.
“ Tension levelling is the ultimate in corrective levelling. The material is run through an entry and exit set of bridle rolls— with the corrective leveller between them. The strip is under great tension with a slight elongation above the yield point of the material and is simultaneously levelled. The material is shape-corrected and relieved of most internal stresses. This process usually involves a dedicated line,” commented Galaxie Corporation.
After levelling, the now-flat metal sheet can be cut to a customer-specified length creating flat sheets or plates that are stable and ready for use.
Cut-to-length lines
Cut-to-length( or CTL) lines are designed to cut coils into flat sheets of specified lengths. A CTL takes flat-rolled steel, or steel coils, unrolls it, levels it and cuts it to a desired length as a sheet. Cut-to-length lines are also known as blanking lines, level lines or shear lines.
The basic parameters of cut-to-length lines( CTL lines) are steel coil width; coil weight; material type; minimum and maximum thickness; tolerance; finished sheet length range and desired flatness. Key features of a line can include precision levellers, roll feed systems, production shears, sheet inspection systems, scrap choppers etc.
These lines are suitable for processing materials such as Cold Rolled( CR); Hot Rolled( HR); Galvanized Iron( GI); Pre-Painted
Galvanized Iron( PPGI); copper; aluminium; stainless steel and other alloys in various thickness ranges. Depending upon the application, CTL lines can be configured for thin( 0.2 – 2mm), medium( 2 – 4mm) or heavy gauge( 5 – 25 + mm) materials. Each CLT is designed to suit specific production volumes, material types and tolerance requirements, making them essential for efficient coil-tosheet transformation.
The specific functions of each component in a CTL line include:
■ Uncoiler: The process starts with an uncoiler, which securely holds the large metal coil and begins to unroll it.
■ Leveller / straightener: After uncoiling, the metal passes through a leveller or straightener. This component uses a series of rollers to remove coil set, waves and any other forms of warping, ensuring that the metal is flat and uniform.
■ Feeder: A precise feeder system, often using servo-driven technology, moves the metal strip forward to the exact length required.
■ Shear: Once the metal has been fed to the correct length, a shear blade or press cuts the strip crosswise to create the desired sheet.
■ Stacker: The final function is the stacker, which collects and arranges the precision cut sheets into orderly stacks, making them ready for packaging, shipping or further processing.
There are many uses for shears in coil processing. A shear is used to crop the tongue off a coil on an entry or exit end of a slitting line, cut-to-length line, pickling line or galvanizing line, used on the entry end of a tube and pipe mill before material is welded together then fed into an accumulator, and used to cut material into sheets on a cutto-length line. Shears are pneumatically, hydraulically or mechanically operated. Popular types of shears in a cut-to-length line are straight cut shears, rotary shears and flying shears.
Slit coil.
Coil slitting lines
Slitting is a process used to cut a wide coil of metal into several narrower strips. The process is primarily used to cut thin materials lengthwise and features a machine fitted with circular blades.
“ In straight mode slitting, the recoiler pulls the material from the uncoiler through slitters. If the uncoiler and slitter are driven only to feed the material to the recoiler, this is called pullthrough slitting. In driven slitting, the slitter is also driven during the process. In this process, the motors are synchronised to maintain a constant speed as the material moves through the line. Driven slitting allows the slitting of thinner sheets and a better edge quality for all thicknesses,” explained coil processing specialist, ThyssenKrupp Materials.
“ In free loop mode slitting, the material forms a free loop between the slitter and the recoiler. A tension device is placed in front of
Image: ThyssenKrupp.
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