Sheet bending and bending machines: how to bend metal

Recommendation points

• How the bending machine works
• Stationary and portable machines
• Differences in metal thickness
• Bend angles
• Segmental machines
• Additional accessories

The listogib gives the roofer great freedom in the independent production of complex elements for valleys, skates, cornices and other interfaces. In this article we will consider some types of bending machines, point out the weak points of the machines and help you choose equipment according to the specifics of the work.

How the bending machine works

In general, the bending machine is a long metal plate, divided longitudinally into two parts. One of them is motionless and rigidly attached to the massive frame. Directly above it there is a pressure beam, which can be easily pulled against a fixed plate and pressed against a sheet of metal. The pressure beam usually has a beveled edge so that the sheet can be folded over 90 °.

The second can tilt up and down, while the axis of rotation is located exactly at the joint. Two plates are like a piano loop: one of them, rising, forms an arbitrary angle with the other. The movable part is called the bender (from the English. to bend – bend), it is connected to the hand drive lever system. If you pull the handle with force, the bender will begin to rise and bend the edge of the metal at the same time along the entire length.

The protractor deserves special attention. In the most primitive models, it is arranged purely mechanically, like a dial on a lever balance: a scale with divisions is fixed immovably to the bed, and the indicating arrow is connected to the bender drive.

Another option: a liquid goniometer – a vertically located annular tube with a colored liquid inside and marks on the outside. The ring is strictly half filled and hermetically sealed, so when it rotates, the liquid level will show the exact deviation in degrees. High and consistent accuracy is a definite plus, but the liquid protractor needs periodic zero position calibration. The wider the ring of the liquid protractor, the higher its accuracy.

In addition to the main nodes, there are additional ones. The pressure beam alone is often tuned for height adjustment, the installation of interchangeable jaws of different lengths or for the use of cutting, rolling and other machines for which the beam acts as a carriage.

Stationary and portable machines

Plate bending machines can be divided into those designed for work in the field, and those that are focused on high productivity. In practice, everything is determined by the weight of the machine as a whole or its largest modules individually. We can say that if a particular master is ready to deliver his machine to the object, it will be portable for him..

As you know, massive metal bending machines have excellent stability, which means that the force for bending will be applied more accurately. Typically, these machines have a heavy cast iron bed, although more often they are simply anchored to a concrete bed. Even thick enough metal (up to 2 mm) can be processed on such equipment. In addition, the less strict weight restrictions, the more powerful and reliable beams, rods and other critical parts can be included in the design..

Portable hand bending machines are usually used by roofers, ventilation installers and finishers. The main limitation is the length of the working beams and, accordingly, the workpieces to be processed. Usually portable machines are lightweight (up to 100-150 kg), their basis is a frame made of a shaped tube, and the length of the working part is limited to 120-160 cm.

Differences in metal thickness

The thicker the metal being bent, the higher the structural load on beams and movable joints. Traction on machine tools for metal up to 2 mm, as a rule, is manual, but the design of the swivel joints and the drive arm may be different.

In repair and construction, metal with a thickness of more than 0.6-0.8 mm is rarely bent on machine tools, usually tin for air ducts and roofing iron fit into these frames. With such insignificant loads, there is no need to provide for a safety margin, almost any breakdown appears as a result of a marriage or technical imperfection of a faulty unit.

The beams of the bending machine for thicker rolled products have a reinforced structure. Usually they are cast and wide, on the back you can see longitudinal and transverse stiffeners. This also applies to most portable machines, where thicker beams have a negative effect on weight. And yet the greatest load falls on the hinge-link mechanisms, especially at the points of attachment to the beams.

Welding is rarely used in such places, usually bolting on intermediate brackets, very similar to the rail system in public transport. In low-grade equipment, these parts are made by powder casting, which is passed off as a superalloy. After a couple of years of active operation, the parts are covered with cracks from the load, and eventually finally break. The price of a listogib is often proportional to the quality of its manufacture.

Bend angles

Almost all common bending models have a bend angle of up to 130–150 °, some up to 160 °. Accurate control of the bend angles is very important for the manufacture of complex and bulky parts such as strips or locks on duct boxes.

It is not always necessary to control the bending angle during operations of the same type; in some bending machines, the drive levers system is equipped with an adjustable limiter. A number of models (LBM) have several such limiters, each of them is configurable and works independently of the others..

But at the same time, it must be remembered that any failures and inconsistencies with the specified values ​​of the angles of the bending produced are usually not the fault of the knocked down goniometer. The most common reasons for this inaccuracy are broken bender hinges and an increased distance between it and the pressure beam..

Segmental machines

In some machines, the pressure beam is equipped with a set of overhead jaws. Some of them can be removed in order to pass the already folded edges at other edges of the sheet under the pressure beam. This is how the sweeps of volumetric parts are processed.

The edges of the jaws do not have to be wedge-shaped. Often they are made semicircular so that when bent, the exact angle is lost and a radius bend is obtained. The accuracy of such machines is far from roller-rolling, but for the manufacture of decorative covers or facade cladding elements, it is quite enough.

The main indicator for a segmental machine is the height of the segments or free clearance. This value determines the maximum width of the folded edges of the workpiece to be machined, which are inserted under the beam..

Additional accessories

A wide range of auxiliary mechanisms are available for bending machines. The most famous is the roller knife, which allows absolutely effortless cutting of the edge of the steel sheet exactly parallel to the edge of the pressure beam.

The rolling machine is no less popular: since the machine cannot bend the edge by 180 ° in one pass, it is first bent at the maximum angle, and then passed between the pressed rollers of the roller.

An edge roll is often used. Usually it is not connected with the main mechanism, just fixed to a massive frame.

The roll is designed to roll the edge of the sheet into a round edge of small diameter, which is useful in the manufacture of gutters and similar long products with high longitudinal rigidity.