How to bend a stainless steel sheet with your own hands

Metal bending is a technological operation in which the product takes the desired size and shape by compressing the internal and stretching the outer layers of the material. As a result, a three-dimensional product is obtained from a flat-shaped workpiece without welds or other seams or joints.

Bending sounds like a simple process, but in reality, it is very complex. The importance of bending in the modern post-industrial world cannot be overestimated. Everywhere you look, there are structures made of bent sheet metal. Even press brake manufacturers are surprised at how complex parts can be produced on the equipment they have developed.

All this became possible thanks to the active implementation of CNC, the use of several controlled axes in bending technology, the latest hydraulic systems and measuring electronics, as well as the widespread use of robots. The main driver of the accelerated development of high-precision bending technology was the widespread transition of the metalworking industry to the use of high-performance punching presses and sheet laser cutting.

Historically, this technological operation arose almost simultaneously with casting and forging - the primary stages of metalworking. Having learned how to correctly bend metal blanks, people solved a huge number of pressing everyday and military problems, ranging from creating complex tools for hunting and agriculture, and ending with the production of weapons.

“Sheet” and “bending” are not very associated with high technology, but in order to bend an “unruly” sheet of metal, special knowledge and enormous practical experience are required. Explain to a technician who is not familiar with sheet metal that in our highly technical world, it is impossible to consistently achieve a 90-degree bending angle without changing settings.

Without changing the program, the angle will change if, for example, a 2 mm thick sheet is made of stainless steel or aluminum, if its length is 500 mm, 1000 mm or 2000 mm, if bending is carried out along or across the grain of the material, if the bending line is surrounded by punched or laser-cut holes, if the sheet has different elastic deformation (hot-rolled steel), if surface hardening during the deformation itself is stronger or weaker, etc. and so on.

Yes, a lot can be said about sheet metal bending as a professional area of ​​metalworking, but perhaps the most important thing should be noted.

1. Sheet metal bending is a highly productive, fast and highly accurate operation.

2. Replacing welding with flexible welding is usually very beneficial when increasing the speed of the production process and providing additional strength to the product due to the so-called stiffeners.

3. Metal bending is rarely a primary operation; as a rule, its task is to bring the part as close as possible to the final form (sales appearance).

4. Bending of complex multi-profile sheet metal products (including flattening and making loops) is very dependent on the use of rare special tools - narrow, curved punches and forging equipment.

5. Bending of workpieces from thick (more than 5 mm) sheets strongly depends on the “tonnage” of the machine, i.e. from such a characteristic as beam force, measured in tons per meter.

6. Bending of small sides (bends) is directly related to the physical characteristics of the metal - its thickness, rigidity and fluidity. So, for example, it is technologically impossible to obtain a 2 mm high bead from a 1 mm thick flexible sheet - you need to use a stamping operation.

7. Also, using a standard cold method to bend a metal workpiece with a thickness of more than 5 mm with an internal corner bending radius less than the thickness of the metal itself is fraught with rupture of the outer plane of the part.

Sheet metal bending in our company is carried out on a 120-ton, 3-meter CNC hydraulic press manufactured by Baycal. The sheet bending machine used in our production has a wide arsenal of equipment (dies and punches), which allow us to fulfill even the most complex orders.

Stainless steel has found wide application in many areas of human activity: construction, automotive industry, tableware production and others. But in order for a stainless steel sheet to turn into a final product, it must be processed: cut, bent, drilled, etc. All these types of processing, despite their apparent simplicity, are complex technological processes that require a professional approach and the availability of special equipment. Even such a seemingly simple process as bending requires high precision and adherence to technology, otherwise the final product is unlikely to be of high quality.

Features of stainless steel bending

Stainless steel is a corrosion-resistant steel. This stability is achieved thanks to special alloying substances included in the steel composition. In addition to protection against corrosion, alloying components can significantly affect the properties of steel: strength, brittleness, ductility, etc. Therefore, when any processing of stainless steel, it is necessary to take into account its grade. Before bending, the steel sheet is usually cut using a laser, high-pressure water jet or other method. During the cutting process, a flat development of the future product is created. Next, the sheet is subjected to bending, during which it is given the required shape. Bending stainless steel sheets is fundamentally no different from bending sheets of ordinary steel, aluminum or other metals. For this purpose, special sheet bending machines or presses are used. Bending of stainless steel sheets is usually carried out in a cold state. If more serious deformations are required, the sheet is heated before bending to avoid damage.

What you need to know about stainless steel bending

For the life of me, I don’t understand the system by which blog posts get likes.
In my opinion, interesting posts practically do not evoke a response from more than a thousand readers, while all sorts of garbage unexpectedly shoots up. Take, for example, the previous post about a device for bending a strip - almost a hundred likes, although it would seem, well, who might be interested in this? But since the topic of homemade equipment is of such interest, keep a fresh device. This time - a device for bending a rod. Again, it was made for a task, namely bending a stainless steel rod with a diameter of 6 mm along a radius of 8 mm at an angle of up to 180 degrees.

As usual, everything was done from pasture, but still not entirely on the knees - three simple turned parts would still be required. During operation, a 6203 bearing is used as a clamp; for simplicity, the rod stop and the guide around which the bending occurs are the same. Under them, on the lower side of the corner, there is a stiffening rib that provides the necessary margin of safety for the entire structure (a little excessive, as tests have shown). Stainless steel M6 bolts, which were lying around in the nightstand, were used as axles. For good measure, they need to be replaced with turned ones for a minimum gap in the mates; bending will be more accurate. But I’ll just cut off the ones I have and put the nuts on the thread lock; for my purposes, ordinary screws are quite enough.

Stainless steel has found wide application in many areas of human activity: construction, automotive industry, tableware production and others. But in order for a stainless steel sheet to turn into a final product, it must be processed: cut, bent, drilled, etc. All these types of processing, despite their apparent simplicity, are complex technological processes that require a professional approach and the availability of special equipment. Even such a seemingly simple process as bending requires high precision and adherence to technology, otherwise the final product is unlikely to be of high quality.

Advantages of bending

Bending is often compared with another common type of metal processing - welding, because... a product created by bending a steel sheet can, in most cases, be manufactured by welding its individual elements together. However, for the production of products that can be made by bending, welding is practically not used. This is explained by the huge number of advantages of bending compared to welding. Among the main advantages of bending are:

• absence of a weld (the least durable structural element);
• lower cost of the product;
• less consumption of materials;
• high production speed;
• more attractive appearance, etc.

It is also worth noting that not only stainless steel can be bent, but also many other materials whose welding is difficult or impossible.

In order for the final product to be of high quality, it is necessary to strictly adhere to the production process and use high-quality equipment. The qualifications of a worker operating a sheet bending machine or press are also subject to high requirements. And, as already noted, before bending or any other processing it is necessary to take into account the grade of stainless steel, because a leaf from it may have specific properties.

Bending sheet metal allows you to obtain a product of the desired shape with relatively little effort. Because welding requires more effort, both physical and financial. A sheet of metal can be bent manually or using automation, but the general principles of operation remain the same. It is the features of this process that will be discussed.

Seals.

If the fitting has a threaded part with a nut, thanks to which it can be secured in the casing body through rubber seals, then the tube of the stainless coil must somehow be passed through the plastic of the casing, and in such a way that water does not leak. For these purposes, I had to make a cunning homemade rubber seal (2 pieces) (see picture) with a groove for plastic.

Using a sharpened large-diameter tube, I cut out two cylindrical seals from thick sheet rubber (thickness about 14mm). Then, using a smaller tube (d < 10mm), central holes were made in each seal (a dashed line passes through them in the figure). Then the seals were mounted on a suitable bolt, the bolt was clamped into a drill and, using a piece of a square needle file, grooves for the plastic were machined (turned, loudly said, rather rubbed) on the rubber seals:

Important! The hole in the plastic of the plumbing pipe covers was drilled in such a way that the rubber seal was inserted into the plastic very tightly. Thus, after insertion, the central hole (which was already made with a diameter of slightly less than 10 mm) was additionally crimped. When inserting the coil tube, the rubber is sandwiched between the coil tube and the plastic hole, thereby sealing the joint. No additional sealants (silicone, etc.) were used.

Basic principles

Metal bending is carried out using various methods. Welding is often used, but temperature exposure can change the shape and properties of the finished product. This reduces performance properties and manufacturing accuracy.

Since when bending metal, the outer layers of the metal stretch, and the inner ones begin to compress, it is necessary to bend part of the rolled metal relative to another by a given angle. The angle can be found using calculations.

The product is deformed to those values ​​that are within the specified limits. They depend on the following parameters:

• Thickness of the metal sheet;
• How much is the bending angle?
• How durable is the material;
• Speed ​​and time of the procedure.

The permissible deformation indicator will depend on them. The next step is to select the type of bending.

Work technology

Step 1. Preparation

Instructions for making a pipe from tin begin with a description of the preparation of the workpiece:

Laying the material on the workbench

1. On a workbench or other flat surface we roll out sheet metal, leveling it using mechanical action if necessary.
2. We measure the length and width of the pipe by marking the material with chalk, marker or marker. When marking, we take into account that the width of the workpiece should be equal to the circumference of the pipe + 1.5...1.6 cm for forming a seam.
3. We control the perpendicularity of the drawn lines using a square.

Cut to size

1. We take scissors and make first a side and then a longitudinal cut. You need to cut strictly along the lines, trying not to make large indents. If the cut line “walks”, problems may arise at the stage of seam formation.
2. Once again we level our workpiece. If necessary, tap the edges to remove waves and process them, removing burrs.

Step 2. Pipe Forming

Now we need to make a round pipe from the blank. And at the first stage we create a profile:

1. On one side of the part we draw a fold line at a distance of 0.5 cm from the edge.
2. On the other side we draw the same line at a distance of 1 cm.

Folding pattern

1. We place the workpiece on a steel corner and bend the folds perpendicular to the plane of the sheet. To bend, use a mallet, adjusting the metal with pliers if necessary.

1. I usually do this: first I grab the metal with pliers, forming a bend about 2-3 cm wide. After the direction of deformation has been set, I change the pliers to a mallet and continue working, using a steel template as a support.
2. When working according to a template, we do not apply excessive force, otherwise we risk damaging the material and “scraping off” part of the protective coating,
3. Next, we divide the bent fold 1 cm wide in half along the width and repeat the fold. Now we need to bend a strip 0.5 cm wide parallel to the main workpiece.

Read also: Speed ​​controller for 380V asynchronous motor

1. Now we form the pipe profile. We place the workpiece on the calibrating surface and tap it, first bending an arc, and then a full circle. The smoother it is, the better - there will be less fiddling around at the final stage of work.

Types of bending of metal products

Metal bending is done manually and using automatic devices. In the first case, the process will be quite labor-intensive, requiring the use of pliers and a hammer, as a result of which this procedure will take a lot of time.

It will be much easier and better to mechanize the process with the help of machines and corresponding devices. The cylinder shape is given to the product by special rollers. With their help, chimneys, gutters, and pipe products are created.

The development of machine tool production has made it possible to achieve bending of material for the manufacture of the most complex products. And the quick replacement of the working tool allows you to reconfigure the machine device as efficiently and quickly as possible.

Creating a sheet metal bending machine

For defect-free bending, you can use homemade mechanisms. You can make them yourself without having additional skills. To do this, you need to create a drawing, prepare materials, tools:

• channels, metal corners;
• pressure plate;
• door hinges;
• wooden block;
• metal rods.

The tools you need are a welding machine, a drill with metal drills, a grinder, and a grinder.

Stages of manufacturing the machine:

1. Initially, you need to prepare the materials, cut the channels, corners, and rods to size using a grinder.
2. Assemble a frame with stable legs. Connect the individual parts using a welding machine. Clean the seams with a sander and coat them with an anti-corrosion compound.
3. Connect two corners with door hinges to create a movable structure.
4. Weld metal rods onto one of the corners to act as handles.
5. Attach the movable structure to the frame so that you can work with workpieces.

Some craftsmen make mechanisms without a base, which are mounted on a finished workbench.

Channel (Photo: Instagram / stockwood.ru_moscow)

Types of equipment

For the modern metal bending process, there are many options for the latest devices. In production, presses are usually used , which can be divided into the following types:

• Rotary, bending metal by moving between special rollers. Suitable for the production of large-sized products in small batches.
• Rotary presses bend the plates using bending beams and two plates. The stationary plate is located at the bottom, and at the top there is a rotating plate. The optimal option for processing sheet metal products with a simple relief and small dimensions.
• Standard pneumatic or hydraulic presses are used for mass or small-scale products made of stainless steel or other metal. Bending is done between the punch and the die. Due to this, even thicker products can be processed. It should be noted that hydraulic presses are used more often than pneumatic ones due to their simpler operation and cost.

Of all the types of equipment described above, the most modern is rotary. It operates automatically, and the worker does not need to calculate the optimal force value in advance.

Rotary presses are also considered automated. Here one sheet is sent to the device, which must be positioned as required by the task. Most often used in small enterprises where they work with metal parts.

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Self-production of the machine

Sometimes you need to make a machine at home . This will make bending metal easier and increase productivity. Here you will need a corner, a metal beam, hinges with bolts, clamps, handles, a table and a welding machine. The procedure is as follows:

1. The base is made of metal; an I-beam profile is suitable.
2. The corner is attached to the top of the beam using bolts.
3. Three hinges are welded under the corner using a welding machine.
4. We bend the aluminum sheet by turning the corner.
5. Two clamps ensure tight pressing of the metal.
6. The corner does not have to be removed; you can raise it. Place the product between the profile and the corner. Then a metal sheet is aligned along the edge.

Check the bolts to ensure they are secure. Turn the crossbars and bend them so as to form the desired angle. This will avoid wasting time on angle calculations.

Whatever the devices, the main principles remain the same . By following them, you can obtain products that meet the standards and wishes of the customer.

During the installation of pipelines for various purposes, as well as building structures based on pipes with a round cross-section or profile, there is often a need to bend pipes to the required radius. There are many ways to do this. The choice depends on the material, wall thickness, diameter, scope of work, and the availability of the necessary equipment. Stainless steel pipes are often used in industrial and individual construction. To bend a stainless steel pipe, you need to apply special knowledge and skills, which will be discussed in this article.

Scheme of stainless steel pipe production technology.

Existing methods for bending metal pipes can be divided into hot and cold, as well as manual and mechanical. It is important to know that stainless steel pipes cannot be hot bent (when heated with a burner), so only cold bending methods will be described.

Pipe bending is usually accompanied by undesirable phenomena that affect subsequent operation. The possibility of their appearance depends on the material, diameter, and method of bending.

Subtleties of handling tin

In order to understand how metal pipes are made and to make your task easier, you should familiarize yourself with some rules for working with this material:

1. To form the ideal pipe shape, a sheet of tin must be wrapped around a cylindrical object (for example, metal or wood), using a hammer and pliers. To get an even bend of the metal along the entire length of the product, it is worth performing light frequent tapping with a slight indentation.
2. Cutting galvanized iron sheets can only be done with special metal scissors. It will be more convenient to work if you attach a leather loop to their ends. Cutting is done with one hand, putting the loop on the fingers.
3. To avoid cutting yourself on a sharp edge, after cutting, the edge of the iron is cleaned with a plane made from an old blade from a hacksaw.
4. In some cases, finished galvanized pipes need to be cut to form a curved edge, for example, when installing drainpipes. For these purposes, it is convenient to use a can opener, having previously filed the beginning of the cut with a hacksaw.
5. A file is also quite often required when working with tin. However, it deteriorates quite quickly because sawdust gets stuck in its ribs. The instrument can be cleaned using a copper spatula or a soft metal tube bent on one side.

Negative consequences of bending:

• Thinning of the outer wall of the bend,
• Formation of folds and kinks on the inner wall,
• Change in the shape of the lumen (ovalization),
• Increase in bending radius after the bending process due to the springing effect.

When a pipe is bent, an uneven change in its cylindrical shape and wall thickness occurs. As a result of metal stresses arising during bending, the outer walls become thinner and the inner walls thicken. With a pronounced thinning of the outer part of the bend, a weakening of the pipe occurs. This is highly undesirable, since the outer wall of the pipeline bend is more exposed to the pressure of the product moving along it.

Another important factor that weakens the pipe after bending is its ovalization. It is especially important to take this into account when installing a pipeline intended to transport a product under pulsating load. When using bent pipes in construction, ovalization also worsens the appearance of the structure. Therefore, when performing bending, they strive to minimize this phenomenon.

Scheme of deformation during pipe bending.

Under the influence of compressive forces arising during bending, thickenings and, in some cases, folds are formed on its inner part. These changes in the shape of the lumen in pipelines increase the resistance to product movement and the likelihood of corrosion, and in addition, lead to a weakening of the pipe as a supporting structure.

Methods to prevent ovalization

Therefore, the main methods of cold bending involve techniques that preserve the original cross-sectional shape of the workpieces. There are two main ways to maintain the original round shape: supporting the wall from the inside - an internal stop and limiting the movement of the side walls of the pipe in the direction of expansion - an external stop.

A calibrating plug (mandrel) or various fillers can be used as an internal limiter. Fillers can be rubber, fusible metals, resins or water. Rigid fillers provide more reliable results in terms of maintaining lumen shape, which is why they are more common. However, when elastic fillers are used, less stretching of the outer side of the bend is observed.

For better preservation of the cross-sectional shape and more precise manufacturing, it is recommended to use simultaneously external and internal stops.

Depending on the volume of work and the diameter of the pipes that need to be bent, either manual devices are used - pipe benders, or machines with an electromechanical drive.

Casing assembly.

We insert the seals into the holes in the plumbing pipe covers. In the same covers, we insert fittings for supplying and discharging cooling water. There is a rubber seal under the fitting nuts for sealing. Next, all rubber seals of the 110th plumbing pipe and couplings are coated with soap for ease of assembly. Then a pipe is inserted into the coupling, a coil is inserted into the pipe, and plumbing pipe caps are placed on both ends of the coil (yes, with those homemade seals). Then, moving the covers along the ends of the coil, we insert the covers into the pipe and coupling. For reliability, I sawed a meter-long stud into two parts and with these half-meter studs I tightened the entire structure with nuts.

Here, in fact, is what happened in the end (general view - top part of the photo, heat exchanger output - bottom left part of the photo, heat exchanger inlet - bottom right part of the photo):

A test run showed that the heat exchanger works successfully. The heat transfer is huge. The water flow can be set to a minimum. It looks like you don't have to worry too much about strong sealing. Since water enters the casing and exits through fittings of the same diameter, the water pressure inside the casing should be minimal.

Mon. _ Alcohol and its solutions, regardless of concentration and quantity, cause enormous damage to the body. I don’t use it and don’t recommend it to others. The coil was assembled to order.

PPN . There are (on the Internet) other ways to seal the joints between the coil tube and the plumbing pipe - for example, using epoxy resin, but then the heat exchanger casing becomes non-separable.

The main industrial methods of cold bending:

• with run-in;
• winding;
• drawing;
• rolling;
• on two supports;
• stretching;
• with internal hydrostatic pressure.

Methods of cold bending of pipes: a - with rolling; b - winding; c - by drawing; g - rolling; d - on two supports; e—stretching; g—with internal hydrostatic pressure; and - through a die having a curved axis; k - by copiers.

In this way, you can bend a pipe with a diameter of up to 150 mm and a significant wall thickness. The principle of the method: around a stationary bending roller of the required size, a rolling roller moves in an arc, pressing the workpiece and performing the bend.

The method has become widespread in pipe billet shops with large volumes of products. Using this method, you can bend a pipe with a diameter from 10 to 426 mm in different planes. To maintain the round shape of the internal cross-section of the workpieces, calibrating plugs (mandrels), solid in the form of a rod or composite, are used.

How to bend a pipe manually

In individual construction conditions, there may be a need to bend a stainless steel pipe by hand. In this case, the possible negative consequences of bending described above should be taken into account.

At home, you can bend a stainless steel pipe using a manual pipe bender. Most often, a pipe bender is used in the form of a crossbow, which bends the workpiece, squeezing it out at the bending point.

To avoid deformation of the lumen, it is necessary to use means of internal resistance to deformation - internal limiters. For these purposes, you can use clean, dry sand. A plug is tightly driven into one end of the pipe, and the gap is filled with sand through the free hole. Then it is also plugged with a plug. Then the pipe is bent around a blank of the required size.

A specially made spring can be used as an internal limiter. It is wound from wire 1 - 4 mm thick so that it fits freely inside the pipe at the intended bend. Bend the pipe with the spring inside around a metal blank or with a manual pipe bender. After this, the spring is removed using a wire previously left outside. This technology is especially useful for bending square-section profile blanks. Accordingly, the spring must also have a square cross-section.

Another option for an internal limiter is a bundle of wire, which is sequentially, one at a time, inserted into the pipe to the bend point. After the work is completed, the wires are also removed one by one.

By hand, you can bend stainless steel pipes with a diameter of no more than 40 mm and a wall thickness of 3 mm. In all other cases, it is necessary to use professional equipment.

Winding.

There are two (main) ways to wind a heat exchanger manually from a stainless tube.

Method one - we fix the improvised shaft (2″ pipe) horizontally and rotate it, thereby winding a stainless steel tube with sand around it.

The second method is to rigidly fix the shaft vertically and wind a stainless tube around it, moving with the tube in a circle.

Because With a four-meter tube you can’t turn around much, so the first option was chosen. And because There is no lathe - so on an improvised workbench, sliding bearings for a two-inch pipe were knocked together from wood:

Important! The upper height limiter (in the picture there is a block with the inscription tree) for such bearings should be equal to the diameter of the shaft (pipe 2″) + one diameter of the wound tube (10mm).

Because a previously cut 3/4″ piece was located perpendicular to the shaft - then by inserting a suitable fitting into it, I got a lever for turning the shaft.

Important! For proper winding, it is necessary to correctly secure the tube to the shaft. You can, as in the video (see above), weld a counterbored nut, insert a stainless tube through the nut, bend the tube 90 degrees and start winding. I didn’t want to get involved with welding (at that time) - so in the shaft itself (2″ pipe) two holes were drilled right through from the edge, through which a U-shaped metal loop was inserted with a twist on the back side, which secured the end of the tube. For additional rigidity, I wound the beginning of the tube with thick wire to the shaft.

Then, slowly, with four hands (one holds the tube, the other turns the shaft using a lever), winding is done, after winding, the choppers are taken out, sand is poured out, an extra piece of tube is sawed off and we get this spiral heat exchanger (the quality of the photo is disgusting, i.e. it was done quickly and by telephone):

As for me, the result of making a coil with your own hands is very, very good, for the first time. It's nice to even hold it in your hands. However, in order for the heat transfer process to be more efficient, the coil turns must be carefully moved apart (so that water also circulates between them). To do this, I had to cut about twenty wedges from dense wood (pine is not suitable) and, using a hammer, gradually driving in the wedges on different sides of the spiral, push the turns of the homemade heat exchanger apart.

Important! At the very beginning, the coils noticeably resist the wedges, so take care of your fingers and nails.

Important!! It is better to move the coils apart in several passes, gradually increasing the distance between the coils and constantly monitoring so that the coil itself does not move to the side:

After all these manipulations we get this beauty (duct tape for scale):

This beauty took three meters of stainless tube. Now it was necessary to make the heat exchanger casing.