Pipe benders and pipe benders: how to bend a pipe

Recommendation points

• How the pipe bender works and works
• Manual and stationary – fundamental differences
• Mechanized and semi-automatic processing
• Weaknesses of pipe benders
• Special pipe benders

When working with frame metal structures, especially when arranging arches and vaults, you cannot do without the use of parts of a radius shape. They can be made using fairly simple equipment – pipe benders. We will tell you about the types and features of pipe benders and pipe bending machines and their choice in the article.

How the pipe bender works and works

To bend a thick metal with muscle force alone, it is reasonable to perform a series of step-by-step deformations of small magnitude with the corresponding applied force. This is the main principle of the pipe bender, a simple analogue of which can be made even at home..

The working part of the machine includes three rollers made of solid steel, arranged in a row at an equal distance from each other. The outer rollers are rigidly fixed to the base of the machine at the same height. The middle roller is slightly raised above them so that a piece of rolled metal is placed in the gap. Technically, you can bend rolled products of any profile (depending on the shape of the rollers), but pipes in construction have to be bent most often. This is where the name of the tool comes from, and the most common form of rollers with a semicircular groove, which the pipe bender is usually equipped with by the manufacturer.

If you apply force to the middle roller, it will transfer it to the pipe and it will bend. If the force is above the elastic threshold (10 kN), structural displacements will occur in the metal, and it will bend so strongly (1:50 mm) that it will not straighten back even after removing the load. It is noteworthy that any shape changes occur only in the working area, that is, the pipe tails, starting from the last point of contact with the roller, will remain practically unchanged..

Effort cannot be increased indefinitely. At such small distances, it is very easy to break the metal structure, therefore any rolled product has a harmless bending radius that is a multiple of the pipe diameter or other basic size. Therefore, the contact point is slightly moved along the pipe, increasing the bend radius to permissible values. It can even be set fixed, based on the value of the applied force and the location of the points at which it is applied – rollers.

This is the main difficulty in bending rolled products with a complex profile: to calculate the required force (or at least fix its current value), the machine must be equipped with auxiliary systems.

Manual and stationary – fundamental differences

A directly ensuing difference between a stationary tool and a manual one is the primitive device of the latter and the absence of any additional systems. The exception is hydraulic pipe benders, in which the force can be determined quite accurately by a pressure gauge indicating the pressure in the piston.

The scope of application also varies. In construction, for example, it may not be important that the metal bends at a critical radius, including at sharp angles. Therefore, for laying metal pipelines, their elements are bent at deliberately overestimated radii in order to guarantee the exclusion of structural violations.

Part size is also of great importance, but not only in the separation of tool classes. On the one hand, in order to process more massive parts, nodes and connections of increased reliability are needed, which make the equipment assembled non-movable. On the other hand, it makes no sense to bend small-sized rolled products on a machine for channel No. 12. Expensive and modern machines do not have this drawback: rollers of different diameters can be rearranged, moreover, the extreme rollers move linearly and the distance between them can, for example, be reduced in order to bend accurately thin bar. This is the whole essence of the pipe bender’s work: do not bend the metal, but bend it.

Mechanized and semi-automatic processing

Using data from special tables, it is possible to make calculations for bending a pipe with a diameter D, wall thickness N at an angle S with a radius R between straight sections. Only four values ​​for a round pipe, but for more complex profiles additional calculations may be required, usually performed by industrial technologists.

Another way is purely experimental. If accuracy is not paramount, but high speed is required, the machine can be made to repeat the sequence of actions just performed by a person, but with a new workpiece, and eventually the program can be completely calibrated..

This requires that the bending process can take place without human intervention. Therefore, for rolling parts, a drive is used on the middle roller or on the two extreme ones, if they are synchronized by the transmission. Muscle strength can be replaced by a geared motor or a hydraulic motor connected to the same oil station with a pressure piston. Mechanized machines do not always have an automatic field, hand tools are equipped with a drive just to save energy.

Weaknesses of pipe benders

Like any mechanical device, pipe benders, and especially pipe bending machines, are not without drawbacks. Some of them are purely technical and are corrected only in the next generation of equipment..

The obvious weak point is the roller bearings, which are quickly depleted under high pressure. It all depends on the quality of the steel – the more expensive the tool, the better. By the mark on the bearing, you can determine its type (optimally roller) and the country of production.

Most other breakdowns occur in the drive end of the machine. Mechanical ones suffer from rapid wear of gears, screws and roller chains. Weak points of hydraulic pipe benders are high pressure hoses and pipes, drums and fittings, other fittings. Over time, even in good hydraulics, leaks can occur, so the need to change the oil or emulsion should be provided for constructively.

The general recommendation for the reliability of the design is as follows: since the pipe bender belongs to a special tool, all its parts should have a narrow purpose. For example, the use of consumer goods (including metric studs) on the adjusting screws is not allowed. Of the types of connections, only hot rivets, special screw pins and roller bushings in movable joints are acceptable. Bicycle or motorcycle chain sprockets, the absence of a special profile thread on the drive screw, and similar parts can also give a fake. The information on the piston nameplate can tell a lot about the manufacturer of the hydraulic tool. It is optimal if the latter looks one piece with the machine body and does not have its own nameplate.

Special pipe benders

The described design is considered the most common, although you can find equipment with a slightly different principle of operation. Grooved roll mandrels remain an almost unchanged trend, but a pipe bender, for example, may not roll metal, but simply push it. If the distance between the rolls is carefully calibrated, the bending angle is determined by the roll offset or the angle of rotation of the drive crank..

In total, there are four ways to bend a pipe: rolling, knurling, winding and hot forming. The first two are relevant in construction, the rest will surely remain the fiefdom of precision industries.