Rebar Shearing and Bending Line

Overview

A rebar shearing and bending line turns a coil of reinforcing steel into the cut, straight, and bent bars that a building site needs, working from a digital bar schedule rather than by hand. Coil bar is cheaper than straight stock and produces almost no offcut waste, but it arrives curved and must be pulled off the coil, flattened, measured, cut to length, and often bent into stirrups or links before it can be tied into a cage. This line does all of that in one pass and at a rate no manual bench can match, which is why precast plants and large rebar shops run them around the clock.

The bar travels through the line in order. The Decoiler and Feed pays it off the coil and pushes it forward, the Straightening Head flattens it, the Length Measuring System system counts off the length, the Hydraulic Shear crops it, and the Bending Head forms any bends. Finished bars drop onto the Output Table table. The Hydraulic Power Unit unit powers the shear and bender, the Control Cabinet cabinet runs the sequence from the cut list, and the Frame and Guarding holds it all in alignment and fences it from the operator.

Decoiling and feeding

The coil sits on the Coil Cradle, a powered turntable that carries two to three tonnes of bar and turns under the pull of the line. A Decoiler Motor drives the cradle so it pays off bar at the right rate, and a Loop Sensor watches the slack loop between the cradle and the line so the two stay matched. Past the loop, a pair of grooved Pinch Roll rolls grip the bar and drag it into the line by friction, driven through the Feed Gearbox. Feeding is the step that sets throughput, so the rolls grip hard and the gearbox is sized to pull bar at speeds up to two metres per second.

Straightening

Coil bar holds the curve of the coil, so it must be flattened before it can be cut to a true length. The Straightening Head passes the bar through two offset rows of hardened Straightening Roller rollers held in a Roller Cassette. The rollers bend the bar past its yield point first one way then the other, with each cycle smaller than the last, so the bar leaves the head straight rather than springing back. Each roller has a Roller Adjuster that sets how deeply it presses, which is how the operator tunes the head to the bar diameter. Heavier lines use a spinning Rotary Straightening Rotor that straightens bar coming off the coil in any plane, which gives a straighter result on large diameters.

Measuring, shearing, and bending

Length is set by the Length Measuring System system. A friction Measuring Wheel rides on the bar and turns an Encoder that counts the length fed, and for short cuts a movable End Stop driven by a Ball Screw on a Linear Guide Rail gives a hard reference. When the programmed length has passed, the Hydraulic Shear fires. Its Shear Cylinder drives the Moving Blade down past the Fixed Blade, cropping the bar with a clean square end; the blade gap is set by shimming the Blade Holder blocks. For bent shapes the Bending Head takes over: a Servo Motor turns the Bending Table so the Bending Pin wraps the bar around the Center Mandrel, and the Bend Angle Encoder reads back the true angle so the controller can correct for springback.

Hydraulics and control

The Hydraulic Power Unit unit supplies the force for cutting and bending. A Hydraulic Pump driven by the Pump Motor draws from the Oil Reservoir and feeds the Valve Manifold, while a Accumulator stores a fast pressure surge for the shear stroke and Pressure Sensor units watch the line. The Control Cabinet cabinet runs the whole sequence: a PLC and I/O imports the bar schedule, an HMI Panel shows the operator each shape and quantity, and Servo Drive units run the bend and stop axes. A hard-wired Emergency Stop Circuit circuit drops pressure and motion if anything goes wrong, backed by the Light Curtain barriers in the Frame and Guarding.

Output and use

Finished bars leave the shear onto the Output Table table, where a Roller Bench supports long bars and a Collection Bin gathers them by shape or length, tipped clear by the Tipping Cylinder. From there bars go to a tying bay to be made into cages or stirrups. The line earns its place on volume and accuracy: it works straight from the structural engineer's bar schedule, holds cut length to a millimetre or two, wastes almost no steel because it works from coil, and runs far faster than cutting and bending bar by hand. Smaller shops run a single combined cut-and-bend machine, while precast plants run several of these lines in parallel feeding a stirrup welder or a cage-welding station downstream.