Combined rebar straightening and bending with ­automatic diameter and bending radii changeover

Since the high quality production standards on all rebar or wire straightening and cutting operations are set with the Melc Rotor Straightening machines, Eurobend moves again one step forward and combines in the Syntheton Series, straightening through Rotor with hyperbolic rollers, non-stop cutting through flying shear together with twin-head bidirectional bending action (left and right bends). Featuring automatic bending radii/tool changeovers up to 10 d and even production of different bending radii in the same bar.

The two servo-driven bending heads can be attached to either any Melc Monoline or Flexiline Series straightening and cutting machine and in accordance with the production schedule the operator can straighten, cut and bend any diameter and/or make stirrups out of any diameter processed (available on the Melc Flexi-Line Series).

In all Syntheton machine versions, the operations of straightening and cutting run simultaneously with the double bending. Thus no mode changes or bar handling is required between the straightening machine and the bending stations. All functions run sequentially without any manual adjustments and operator involvement.

Straightening and feeding simultaneously

In the case of a Syntheton machine version equipped with a Melc Flexiline, straightening system, diameter changeovers are also automatic and controlled via the computer using simple windows-based software.

The straightening method of the Melc Monoline and Flexi Line Series: The straightening method adopted is based on the Rotor straightening principle, introduced by Eurobend engineers in the early eighties. All straightening and cutting machines operate on two different principles:

a) Two plane roller configuration, at 90˚ to each other,

b) Conventional Rotor straightening with dies.

The advantages and disadvantages of the systems are known, mainly the first does not produce quality straightness and damages the rebar surface with extreme pressure on the rebar, while starting and stopping for cutting, and the second generates too much heat, due to friction, that reverses any good straightness produced at the rotor and damages the rebar surface.

The method is based on the Rotor straightening system, but instead of dies, Eurobend has placed hyperbolically profiled steel rollers. The cylinders execute the two fundamental operations of straightening and feeding simultaneously. This is achieved by positioning the cylinders at an angle to the rebar and rotating them round the rebar, so at the same time accomplish feeding and straightening.

The placement of the rollers at an angle to the rebar axis, results in line contact with the rebar surface and not point contact as in conventional rotors. Also, when the Rotor is spinning and the rollers are feeding the rebar through, there is no sliding friction – only rolling friction – thus the rebar surface is not damaged.

Machine downtime ­minimized

Eurobend’s straightening method ensures better straightening quality and consistency, which is something that cannot be found in the competition, since continuous wear of the dies, or the conventional rollers, cannot be avoided.

The Eurobend Melc straightening system outperforms competitor’s machines and provides excellent straightening results even when processing high ductility material (ductility class “C”).

The advantages:

The “Melc” straightening and cutting machines have a number of advantages that are briefly described below:

1. Machine downtime is minimized, since continuous adjustment of the straightening mechanism is not needed.

2. Straightening of high tensile steel (PC wire up to 1800 N/mm² UTS) has been achieved and the difficulties were overcome easily with less expenses.

3. Mechanical simplicity of machine construction, due to the simultaneous feeding and straightening, results in a machine with stable, constant and continuous operation.

4. Cutting of the required length is achieved with flying shear cutter, while the rebar is moving, without having to start and stop, or to slow down the speed of the rebar, in order to cut.

5. The simplicity of the design allows the construction of multi-line machines (up to six Rotors) depending on the productivity requirements and the diameter ranges of each customer. Each line works independent from the others and any combination or all of them can work together. Each has a dedicated collector bin and can cut the same or different lengths.

6. By designing the right hyperbolic profile (curvature) of the roller, combined with the proper surface treatment of the roller and more rarely the proper coating, we can achieve the desired surface finish on the straightened rebar surface.

Each rotor usually is preset for working with one up to four different diameters, according to the customer productivity requirements. With multi-Rotor configuration machines production speeds of up to 500 m/min have been achieved.

Depending on the required output, there are different types of Melc straightening & cutting machines available, using our latest fourth generation rotor such as:

Melc Monoline series

Single line straightening and cutting machines, capable of achieving speeds of up to 120 m/min. Speed is adjusted by Frequency inverter controls, thus the machine adapts the output to the required productivity needs, where at the same time parts life cycle maximized and downtime minimized.

Coil diameter changes can be achieved in less than five minutes due to the special preset system used. There are special application modules available, for rebar twist control and surface finish control (patented) making the Melc Monoline series ideal for high tensile (or stainless steel) rebar straightening.

Melc Flexiline series

Automatic rebar straightening and cutting machine, processing up to six interchangeable coils. All Melc Flexiline straightening & cutting machines are equipped with our unique convergence guide system for automatic rebar diameter/coil changes in seconds (patented). The extremely fast and automatic coil changes, enables the production of different rebar diameters in the same batch without complicated collection systems. A flying shear cutter, common to all lines, allows uninterrupted operation and minimizes material stresses.

Equipped also with industrial microprocessor controls and user-friendly operation using advanced Windows based software. The Melc Flexiline straightening and cutting machines are available in various multi-line configurations, from three up to six lines, processing rebar sizes from 8 mm up to 25 mm.