Cut-to-Length Line

Overview

A cut-to-length line turns a coil of metal strip into a stack of flat, square sheets cut to an exact length. The strip is paid off a reel, pulled straight, flattened in a roller leveler, fed forward in measured steps and sheared across its width, after which each sheet is conveyed to a stack. The whole machine exists to do two things well: make the sheet truly flat, and cut it to a length that holds tolerance over thousands of cuts. Steel, stainless, aluminum and coated products all run on the same line with recipe changes for tension, leveler intermesh and blade gap.

The line is laid out in process order. The Entry Section handles the coil, the Pinch and Feed Section grips and centers the strip, the Roller Leveler flattens it, the Loop Pit holds slack, the Servo Roll Feeder meters length, the Flying Shear cuts, and the Stacker and Exit Conveyor piles the sheets. Behind all of this sit the Hydraulic Power Unit and the Drive and Control System, carried on a common Machine Frame.

Entry and pay-off

The coil arrives on the Coil Loading Car, a hydraulic V-saddle car that lifts the coil and presents its bore to the Expanding Mandrel of the Uncoiler. The mandrel expands inside the coil bore through its Mandrel Expansion Cylinder, and a Servo Motor holds back-tension so the strip pays off without slack. The Peeler and Threading Table lifts the loose head end off the wrap and threads it across the Threading Table, while the Hold-Down and Snubber Roll presses the wrap to stop the coil from springing open.

Feed and leveling

From the reel the strip enters the Entry Pinch Roll Unit, which drives it forward, and the Strip Edge Guide, which keeps it centered using Edge Position Sensor feedback so the sheets come off square. The strip then runs into the Roller Leveler, the part that decides sheet flatness. Inside the Leveler Roll Cassette a row of small Leveling Work Roll rolls bends the strip alternately up and down. Small diameter matters: a thin roll bends the strip sharply, which is what drives the surface fibers past yield and erases coil set. Because such slender rolls would deflect under load, each is propped by Backup Roll rolls. How far the upper rolls reach down between the lower rolls is set by the Intermesh Adjustment Actuator through its Intermesh Adjusting Screw, with the gap read back by a Roll Position Transducer. The whole cassette is a quick-change unit pulled on the Cassette Change Cradle when a different product needs a different roll set.

Loop and length measurement

The leveler runs continuously, but the shear cuts in stops and starts, so the two are decoupled by the Loop Pit. A free loop of strip hangs in a lined floor pit, and Loop Height Sensor units watch its depth so the leveler entry speed and the feeder pull speed stay balanced. Downstream the Servo Roll Feeder pulls a measured length of strip and stops it dead. Its Feed Roll rolls advance the strip while a separate Measuring Roll reads true fed length on a Length Encoder, independent of any roll slip. Between cuts the Feeder Release Clamp lifts so the strip floats free while the shear works.

Shearing

The Flying Shear cuts the sheet to length. The Upper Shear Blade and Lower Shear Blade are tool steel, and the clearance between them is set for strip thickness and grade by the Blade Gap Adjuster. The cut is driven by the Shear Cutting Cylinder pair while the Shear Hold-Down Clamp pins the strip flat so the cut edge stays square. On a flying shear the Shear Carriage accelerates the whole shear up to line speed during the cut, so the strip never has to stop, which is how high cut rates are reached.

Stacking and support

Each cut sheet is caught by the Magnetic Belt Conveyor, whose Magnet Bar elements hold the steel against the belt and carry it clear of the shear. At the Drop Stacker the magnetic hold is broken so the sheet falls onto the Stacking Table, which lowers as the pile grows and squares it with side and back gauges. Defect sheets and the leading scrap end are thrown aside by the Scrap Ejector before they reach the stack. Hydraulic power for the shear stroke and the mandrel comes from the Hydraulic Power Unit, with an Bladder Accumulator giving the shear a fast stroke. The Drive and Control System ties it together: the Length Cut Controller fires the shear at the measured length and counts sheets per batch, the Line PLC runs the line sequence, and the operator sets cut-length recipes at the Operator HMI.