MesterulManole
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MesterulManole July 25, 2016Specialization: many years of experience in finishing works of residential and office premises, dachas, country cottages, etc. Hobby: cycling in all its forms
Preheating of the deformable area
Hello dear readers. Today I’ll tell you how to bend a pipe without a pipe bender and with a pipe bender, and how to bend a polypropylene pipe. The topic is of considerable interest since without bent pipes it is difficult to build a greenhouse, gazebo or canopy over the porch.
Selecting a bend method
How to bend a pipe with your own hands? The question is not an easy one. When bending this product yourself, first of all, it is important to take into account the fact that during this process radial and tangential forces arise in the profiled metal, the impact of which can lead to rupture of the section and the appearance of folds on it.
To prevent this from happening, when forming a bend, it is necessary to take into account all the parameters of this process.
The technology that can be applied in each specific case is selected based on:
- Pipe material;
- Its size;
- Required bend angle and radius.
Having made a preliminary assessment of these parameters, you should choose one of the options proposed below. The photos below will help you understand the correct implementation of each of them, demonstrating step by step how to bend a pipe.
Heat
When exposed to high temperatures, many metals and their alloys become more ductile and less deformable. This rule applies to aluminum, duralumin, steel, copper, brass products and aluminum-ferrous bronze workpieces.
- When heating pipes made of tin bronze, gray cast iron or zinc alloys, you can get the exact opposite effect - they become more brittle when heated.
- It follows from this that not just any pipe can be heated for bending.
- It is possible to heat galvanized pipes, since their coating is not damaged in this case.
- When heating the product, you should not get too carried away, because under the influence of too high temperatures, oxygen begins to penetrate into the material, which entails its oxidation - an irreversible process that destroys the pipe. As an example, we can consider bending an aluminum billet.
- We heat the bending surface and bring a sheet of paper to it. If it lights up, the product can be bent.
As an indicator of the degree of heating of structures made of steel, their reddening to the state of scale can be used.
Protection against ovalization
The main methods of cold bending a galvanized pipe involve measures that allow the workpiece to be bent while preserving the shape of its cross-section as much as possible. Typically one of two methods is used for this:
- The use of measures to preserve the shape of the section from the inside (use of an internal limiter).
- Using an external stop to prevent expansion of the side walls.
Rigid materials as fillers retain their shape better, so they are used more often. But thanks to the use of elastic fillers, less stretching of the outer surface of the bend occurs.
Filling with water or sand
Water is poured into the cavity of the workpiece, after which plugs are installed at both ends and cold is placed so that it freezes.
The product is bent by subsequently heating it with a gas burner. This method is not suitable for pipes that have a galvanized coating, as it can lead to damage.
The method using sand is applicable to pipes with a large cross-section or square configuration. Its essence lies in the preliminary filling of the workpiece cavity with sand. Then the pipe is thoroughly heated and bent by tapping it with a mallet. No heat is required to bend galvanized structures.
Work at home without a machine
It will be possible to obtain the required bend from a profile pipe without special equipment. All you need is a grinder, a welding machine and yews. The algorithm will be as follows:
- measure out the required pattern, and then draw a template on a free plane;
- We apply the workpiece to it and mark the bending point on it;
- we file three sides of the square profile, and on the fourth you will need to bend the pipe without a pipe bender, clamping the free end into a yew;
- then we weld the resulting part in this position;
- After welding, the seams are cleaned and the workpieces are mounted in the intended location.
Before welding a 2 mm profile pipe, the welder must use protective equipment. We experimentally set the current on the welding machine to use electrodes with a diameter of 3 or 2 mm. Large ones are not suitable here, since if you weld a profile pipe, for example, with a “four”, the cavity will simply be burned through.
Using Templates
This method is suitable for making complex pipe bends. The simplest template can be a piece of wire, pre-bent in accordance with how the product will be bent.
If it is possible to place the bent pipe section on a plane, self-tapping screws twisted into a piece of plywood can act as a kind of template. Bending is done gradually, checking the resulting result with the template from time to time.
Application of rolls
This method is suitable for bending a metal profile. It is good because its use reduces friction on the surface of the product and reduces the risk of unwanted deformation.
As a result, much less effort has to be applied to obtain the desired bend, and damage to the part is minimized.
Using rolls, you can make your own pipe bender for bending pipes, allowing you to avoid the use of long parts. The three-roller version is most often used. Two rollers located in it play the role of outer supports, and the third one presses into the center of the fold.
This homemade device allows you to process round pipes, rectangular profiles, as well as plates and corners. Using it, you can bend the same radius over a fairly large length of the workpiece.
Industrial cold bending methods
Depending on the diameter of the element and the volume of work, hand tools (pipe benders) or devices with an electromechanical drive can be used.
Basic industrial cold bending methods:
- Winding method. This technique allows you to bend a pipe with a cross-section in the range of 1.0-4.26 cm in different planes. To maintain the shape of the section, composite or rod mandrels are used - calibrating plugs.
- With a run-in. This method is suitable for bending tubular elements with a diameter of no more than 15 cm. In this case, the wall thickness should be impressive. The essence of the method: a rolling roller moves around a static bending roller of a given size. He presses the pipe and bends it.
- Rolling. This method allows you to bend the workpiece in a spiral or into a ring. On rollers, the element is moved by rollers and acquires the curvature specified by the position of the rollers.
- By dragging. The method is suitable for bending thin-walled, seamless products. For bending, a template is made from a tubular element of larger diameter. The template is then threaded through the die and secured with a clamp. Due to the rotation of the template, the workpiece is pulled through the die and bent.
- By stretching. This technique allows you to minimize the risk of metal deformation. To do this, the workpiece is fixed at the edges, stretched and bent simultaneously through the use of a bending template.
- On supports. Typically, two supports are used on which the workpiece is laid. As the supports bend, they rotate around their axis. The template is connected to the jack rod so that the force is applied in the center of the workpiece. The method is suitable for bending tubular products with a diameter of no more than 35.1 cm. The equipment allows bending to be performed directly on the construction site.
- With hydrostatic pressure inside. To do this, liquid is injected into the tubular element. Plugs are installed at the ends. Due to the stresses that arise, the metal reaches an almost plastic state. Then a template is brought to the bending point and the workpiece is bent.
- With pushing. The method is suitable for bending elements with a diameter within three inches. The workpiece is pushed through a fixed and movable die. Due to the displacement of the matrices relative to each other, the curvature of the bend can be adjusted. Using this technique, one workpiece can be bent several times in different planes.
As for the use of mandrels, the simplest plug for pipes with a cross-section of no more than 3.2 cm can be a steel cable. One end of this cable is fixed in the handle. The other end is connected to the wire to pull into the lumen. In this case, the diameter of the calibrating plug should be slightly smaller than the cross-section of the tubular product - approximately 0.1-0.5 mm.
When using calibration plugs, unwanted scratches and nicks may occur on the inner surface of the workpiece. This usually happens when bending stainless steel products. To protect against such undesirable consequences, you need to choose the right material for making the cork, as well as use lubricant and thoroughly clean the surface.
Spring
The essence of this option is to place a spring of the required diameter, made of steel, into a bendable workpiece.
When bending, it holds the pipe, preventing it from being deformed incorrectly. The pre-profile element with a spring inserted into it is heated and then bent using pliers.
In certain cases, the spring can be replaced with a wire. Its bundle is installed in the pipe in separate pieces, and after the bend is completed, it is gradually pulled out.
Profile pipes
Profile pipes can have square, oval and rectangular configurations. It is quite difficult to bend them without violating the technical specifications. The most successful option for carrying out the work would be to use welding with preliminary filing of the walls of the workpiece with a grinder where the bend is planned.
Moreover, it would be advisable to first make cuts and bend the workpiece, and then weld the seams. If the part has a small diameter, then a regular soldering iron will do instead of welding.
What is the difficulty of bending profiles?
The essence of bending rolled metal, regardless of the shape of its profile, is that the profile pipes are given a partial or full bend. This technological operation is performed in two ways: by acting on the pipe being bent only by pressure or by additionally heating the section of the pipe in the area of which the bend is performed. During bending, two forces simultaneously act on a metal pipe:
- compression force (from the inside of the bend);
- tensile force (from the outer part of the bending section).
It is the influence of such multidirectional forces that causes the difficulties characteristic of the process of bending any profile pipes.
- Segments of the pipe material, which changes its shape during the bending process, may lose the coaxiality of their location, which leads to the fact that individual sections of the pipe will be located in different planes;
- The wall of the corrugated pipe, located on the outside of the bend and subject to tension, may not withstand the load and burst.
- The inner wall of the pipe, subjected to compression, may become covered with folds that resemble corrugation.
Technical characteristics of profile pipes
If you do not take into account the subtleties of such a technological process, then instead of bending a profile pipe, you can simply crush the product, ruining it irrevocably.
To prevent this from happening, it is necessary to take into account not only the characteristics of the pipe material, but also its geometric parameters - cross-sectional dimensions, wall thickness, radius to which the bend must be made. Knowledge of the above will allow you to choose the appropriate technology and bend the corrugated pipe correctly, without crushing it and without getting a corrugated surface.
Metal-plastic pipes
They bend well by hand without requiring heating. The main thing is to ensure that the workpiece does not become excessively bent.
To perform the bend, you can also use wire by inserting it into the cavity of the metal-plastic pipe being bent, or connect heating to this procedure, while controlling the resulting temperature with a paper sheet.
Pipe benders for profile and round products
Pipe benders for steel and copper pipes are:
- manual,
- mechanical.
Moreover, whether it is a manual or mechanical type determines both the design features of the pipe bender and its performance.
Manual devices
The manual pipe bender consists of:
- beds,
- conveyor,
- clamping element.
The pipe is inserted into a conveyor consisting of rollers connected by a chain transmission, and is pressed by the upper (or lower) roller, which presses on the corresponding edge of the product. By rotating the handle of the feed rollers, you can move a measuring length through the pressure zone, and as a result, bend a profile pipe or a similar round-shaped product.
However, the manual process has its own nuances. Firstly, it is still possible to bend a profile pipe with your own hands, but to achieve the result you need to apply significant effort. Secondly, manual pipe benders are suitable for processing only small batches of products.
Mechanical apparatus
The mechanical apparatus saves us from the need to waste our energy bending the profile pipe to the desired radius. After all, in a mechanical pipe bender, both the conveyor and the clamping element operate not from the muscular strength of the operator, but from an electric motor and a hydraulic drive.
In this case, the operation scheme of the device remains unchanged. That is, as in the first case, we fill the conveyor with a pipe, create a pressing force on the plane of the product being bent (where the profile pipe must be bent even before the measuring segment begins to move along the conveyor) and turn on the device in the network. As a result, the pipe passes the pressure roller zone and changes its curvature. The process of manual and mechanical bending will be discussed in more detail below.
