Wood bending. How to bend a wooden block? Methods for bending wooden corners at home

If there is a need to create a curved wooden element, then most likely you will encounter a number of difficulties. It may seem easier to saw the required component in a curved shape, but in this case the wood fibers will be cut and weaken the strength of the part. In addition, during execution, a rather large overrun of material is obtained.

Stages of work on bending the board at home:

	Training. Choice suitable variety tree and familiarization with the general principles of working with it.
	Options for bending wood. Heating in a steam box, chemical impregnation, delamination, propyl.

Wood is cellulose fibers bound together by lignin. The arrangement of the fibers in a straight line affects the flexibility of the wood material.

Tip: a reliable and durable wood material for creating various products can only be obtained if the wood is well dried. However, the change in the form of dry wooden blank- a rather complicated process, since a dry tree can easily break.

Having studied the technology of wood bending, including its main physical properties wood, allowing you to change its shape, it is quite possible to perform bending wooden material at home.

Features of working with wood

Bending of a wooden material is accompanied by its deformation, stretching of the outer layers and compression of the inner ones. It happens that the tensile force leads to rupture of the outer fibers. This can be prevented if a preliminary hydrothermal treatment is carried out.

It is possible to bend blanks of timber made of glued wood and solid wood. In addition, peeled and sliced ​​veneer is used to give the necessary shape. The most plastic is hardwood. Which includes beech, birch, hornbeam, ash, maple, oak, linden, poplar and alder. Glued bent blanks are best made from birch veneer. It should be noted that in the total volume of such blanks, about 60% falls on birch veneer.

According to the manufacturing technology of bent wood, when steaming a workpiece, its ability to compress significantly increases, namely by a third, while the possibility of stretching increases by only a few percent. Therefore, you can’t even think about bending a tree thicker than 2 cm.

How to bend a board at home: heating in a steam box

First you need to prepare a steam box, which can be DIY. Its main task is to hold the tree that needs to be bent. It must have a hole for steam to escape. Otherwise, under pressure, an explosion may occur.

This hole should be in the bottom of the box. In addition, a removable lid must be provided in the box, through which it will be possible to remove the bent wood after it has received the desired shape. In order to hold the bent wood blank in the required shape, it is necessary to use special clamps. They can be made independently from wood or purchased at a hardware store.

Several round scraps are made from wood. Holes are drilled in them, offset from the center. After that, you should push the bolts through them, and then drill another one through the sides in order to push them tightly. Such simple crafts can perfectly serve as clips.

Now you can start steaming the tree. To do this, you need to close the wooden blank in the steam box and take care of the heat source. For every 2.5 cm of product thickness, the time spent on steaming is about an hour. After it expires, the tree should be removed from the box and given the desired shape by bending. The process should be carried out very quickly, and the bending itself should be soft and accurate.

Tip: due to varying degrees of elasticity, some types of wood will bend more easily than others. different ways require the application of different amounts of force.

As soon as the desired result is achieved, the bent workpiece must be fixed in this position. Fastening a tree is possible during the process of its formation new form, due to which it will become much easier to control the process.

How to bend a board at home using chemical impregnation

Since lignin is responsible for the durability of wood, its bonds with the fibers should be destroyed. This can be achieved by chemical means, and it is quite possible to do this at home. Ammonia is best suited for such purposes. The workpiece is soaked in a 25% aqueous solution of ammonia, which greatly increases its elasticity. Thus, it will be possible to bend, twist it or squeeze out any relief forms under pressure.

Tip: you should pay attention to the fact that ammonia is dangerous! Therefore, in the process of working with it, you must strictly adhere to all safety regulations. Soaking wood should be carried out in a tightly closed container, which is located in a well-ventilated area.

The longer the wood is soaked in an ammonia solution, the more plastic it will become later. After soaking the workpiece and forming its new shape, it should be left in a similar curved form. This is necessary not only for fixing the shape, but also for the evaporation of ammonia. However, you need to leave the bent tree in a ventilated area. Interestingly, when the ammonia has evaporated, the wood fibers will regain the same strength as before, allowing the workpiece to hold its shape!

How to bend a board at home: a layering method

First, you need to harvest wood, which will later be subject to bending. It is imperative that the boards are slightly longer than the length of the piece required. This is because the bend tames the lamellae. Before you start cutting, you will need to draw a diagonal line with a pencil. This must be done across the underside of the workpiece, which will make it possible, after moving the lamellas, to maintain their sequence.

The boards must be cut with a straight edge, and not with the right side. Thus, they can be put together with the least change. The cork layer is applied to the mold, which will help to avoid any irregularities in the shape of the saw and will make it possible to make a more even bend. In addition, the cork will hold the delamination in shape. After that, glue is applied to the upper side of one of the lamellas with a roller.

It is best to use a two-part urea-formaldehyde adhesive. He has high level clutch, but takes a long time to dry.

You can also use epoxy resin, but such a composition will be very expensive, and not everyone can afford it. The standard version of wood glue in this case will not work. Although it dries quickly, it is very soft, which in this case is not welcome at all.

The bent wood product must be placed into the mold as soon as possible. So, on a lamella smeared with glue, another one is laid. The process must be repeated until the bent workpiece receives desired thickness. The boards are attached together. After the glue has completely dried, it should be shortened to the required length.

How to bend a board at home: propyl

The prepared wooden piece must be sawn through. Cuts are calculated for 2/3 of the thickness of the workpiece. They should be located on the inside of the bend. You need to be extremely careful, as rough cuts can not easily deform the tree, but completely break it.

Tip: The key to success when cutting is to keep the distance between the cuts as even as possible. The ideal option is 1.25 cm.

The cuts are made across the wood pattern. Then it is necessary to compress the edges of the workpiece, which will allow you to connect the resulting gaps into one. A similar shape and gets a bend at the end of the work. After that it is corrected.

In most cases, the outer side is treated with veneer, less often with laminate. This action makes it possible to correct the bend and hide almost any defects made during the manufacturing process. Gaps in a bent tree are hidden very simply - for this, sawdust and glue are mixed, after which the gaps are filled with the mixture.

Regardless of the fold option, after the workpiece is taken out of the mold, the fold will relax a little. In view of this, it should be made slightly larger in order to subsequently compensate for this effect. The sawing method is used when bending a metal corner or part of a box.

So, using such recommendations, you can bend the tree with your own hands without any special problems.

If you decide to decorate the room with wood or start creating beautiful furniture in a classic style - then you will need to make curvilinear parts. Luckily, wood is a unique substance, as it allows the experienced craftsman to play with the shape a bit. It's not as difficult as it seems, but it's not as easy as you'd like.

Previously, the site already had a publication on plywood bending. In this article, we will understand the principles of bending massive boards and timber, learn how it is done in production. We will also bring helpful tips from professionals who will be useful to the home craftsman.

Why bending is better than sawing

curvilinear wooden detail can be obtained in two ways: by bending a flat workpiece, or by cutting out the required spatial shape. The so-called "cutting" method attracts users with its simplicity. For such manufacture of parts and structures, you do not need to use complex devices, you do not have to spend a lot of time and effort. However, in order to cut a curved wooden product, it is necessary to use a workpiece that is obviously too large, and a lot of valuable material will be irretrievably lost as waste.

But main problem are the performance characteristics of the parts received. When cutting a curved part from a conventional edged lumber, wood fibers do not change their direction.
As a result, transverse sections fall into the zone of radii, which not only worsen appearance, but also significantly complicate the subsequent refinement of the product, for example, its milling or fine grinding. In addition, in the rounded areas most vulnerable to mechanical impact, the fibers run across the section, which makes the part prone to breaking in this place.

Whereas when bending, the opposite picture is usually observed, when the wood only becomes stronger. On the edges of a curved beam or board do not go "end" sections of the fibers, so subsequently it is possible to process such blanks without restrictions, using all standard operations.

What happens in wood when it bends

The technology of bending is based on the ability of wood, while maintaining integrity, to change its shape within certain limits as force is applied, and then retain it after removal of mechanical stress. However, we all know that without preparatory activities lumber is elastic - that is, it returns to its original state. And if the applied forces are too great, then the beam or board simply breaks.

The layers of a wooden blank work differently when bent. Outside the radius, the material is stretched, inside it is compressed, and in the middle of the array, the fibers practically do not experience significant loads and have little resistance to the forces acting on the workpiece (this inner layer is called “neutral”). Under critical deformation, the fibers on the outer radius are broken, and on the inner radius, “folds” are usually formed, which are a fairly common defect in the bending of softwood. The fibers of plastic hardwood or softwood can shrink by 20 percent or more, while the stretch limit is about one to one and a half percent.

That is, to determine the possibility for bending (without breaking), the limit of relative elongation of the stretched layer will be a more important indicator. It directly depends on the thickness of the part and determines the radius to be obtained. The thicker the workpiece and the smaller the radius, the greater will be the relative elongation along the fibers. Having data on the physical properties of popular wood species, it is possible to formulate for each of them the maximum possible ratio of the thickness and radius of the parts. In numbers it will look like this:

Bending using a steel bar

Bending without using a bar

These data indicate that softwood lumber, in comparison with dense hardwood, is less adapted to free bending. To work with lumber at aggressive radii, it is imperative to use combined methods of preliminary preparation of parts and mechanical protection.

Tire as an effective way to avoid the destruction of wood during bending

Since the main problem is the breakage of the fibers from the outer radius, it is this surface of the workpiece that needs to be stabilized somehow. One of the most common methods is the use of an overhead tire. The tire is a steel strip with a thickness of half a millimeter to two millimeters, which covers a beam or board along the outer radius and is bent on a template along with the wood. The elastic strip absorbs part of the energy during stretching and at the same time redistributes the breaking load along the length of the workpiece. Thanks to this approach, coupled with moistening and heating, the allowable bending radius is significantly reduced.

In parallel with the use of a steel tire in bending devices and machines, mechanical compaction of wood is achieved. This is done using a pressing roller, which presses on the workpiece along the outer bending radius. In addition, the template mold in such a fixture is often endowed with 3 mm teeth (in increments of about 0.5 cm), oriented towards the workpiece travel.

The task of the jagged surface of the template is to prevent the workpiece from slipping, to prevent the mutual shift of the fibers in the solid wood, and also to create a small depressed corrugation in the concave radius of the part (the fibers are pressed into the array, therefore, problems with folds are solved).

Pressing with a tire allows you to bend bars and boards from softwood and soft hardwood with a minimum percentage of rejects. Please note that parts made of relatively hard rocks become about ten to twelve percent thinner when bending with pressing, and pine and spruce blanks become 20-30% thinner. But the positive aspects of this method include a significant increase strength characteristics finished product, as well as a significant reduction in the requirements for the presence of flaws and defects in wood blanks.

How to improve the plasticity of wood

In the normal state, lumber has elasticity, significant spatial rigidity and resistance to compression. Wood receives these valuable properties from lignin, a natural "network" polymer that gives plants a stable shape and strength. Lignin is located in the intercellular space and in cell walls, connecting cellulose fibers. In coniferous wood it contains about 23-38 percent, in hardwood - up to 25 percent.

Essentially, lignin is a kind of glue. We can soften it and turn it into a "colloidal solution" if we heat the lumber by steaming, boiling, treating with high frequency current (a household microwave is also applicable for small parts). After the lignin is melted, the workpiece is bent and fixed - cooling down, the molten lignin hardens and prevents the wood from returning to its original shape.

Practice shows that the optimum temperature for bending solid wood (bar, rail, board) will be 100 degrees Celsius. This temperature must be obtained not on the surface, but inside the workpiece. Therefore, in many respects, the time of thermal exposure will depend on how massive the part is. The thicker the part, the longer it will take to heat up. For example, if steaming is used to prepare a 25 mm thick strip (with a moisture content of about 28-32%) for bending, then on average it takes about 60 minutes. It is noteworthy that the exposure time under steam for parts of similar dimensions for any species is approximately the same.

By the way, it is believed that it is also impossible to overheat the part, since lignin after hardening can lose elasticity and become too brittle.

The boiling method is not often used, since the workpiece is strongly and unevenly moistened, and such water-saturated fibers and cells, when bent, can tear, at least with the formation of a pile. Parts after cooking have to dry for too long. But this method shows itself well if you need to process only part of the workpiece for bending.

Steaming allows you to heat the workpiece evenly, and its humidity at the exit tends to approach the optimum. The most suitable humidity for achieving maximum plasticity of lumber is considered to be in the range of 26-35 percent (the saturation point of the wood fibers).

To steam wood for bending at home, use home-made cylindrical chambers made of metal / polymer pipes or rectangular wooden boxes. Heating tanks act as a source of steam, electric kettles and other similar devices that can provide a temperature of about 105 degrees and a little pressure. This is always followed by the stage of drying the part (+ exposure of the fixed form) to about fifteen percent and its finishing.

Chemical methods of plasticizing wood

It is also known that it is possible to make lumber more pliable using impregnation with various compositions. There are ready-made impregnations that make wood cells more plastic, for example, Super-Soft 2. Some practitioners soak wood in so-called textile conditioners, with similar results.

But rather primitive “recipes” containing ammonia and ethyl alcohol, glycerin, alkalis, hydrogen peroxide, dissolved alum can also be used ... Many of them are extremely simple - they increase the ability of the workpiece to absorb water and help retain moisture in the fibers.

Thin products such as veneer are spray treated, but pre-treatment of normal lumber with chemicals is usually done by full immersion. It takes time for the working substances to get inside the bar or rail, usually it takes from 3-5 hours to several days (although heating helps to reduce the wait).

It is largely because of the duration of the processes that chemical plasticization is not often used, although there are other problems: the cost of chemistry, color changes, the need to provide protection from harmful fumes, the increased tendency of such curved parts to straighten ...

Tips for bending lumber using hydrothermal preparation

• Very carefully select the quality of the workpiece for bending. It is better not to use material with cracks, knots (even live and intergrown), fiber inclination. If there are no options for this, then orient the part in the bending fixture (machine or template) so that the defects fall into the concave radius zone, and not into the tension zone on the outer radius. Give preference to the bending method with a bar.
• When selecting a workpiece, it is imperative to provide for a change in the size of the part after molding. For example, the thickness of a coniferous bar can be reduced by 30 percent if bending with pressing is performed.
• Even if you are planning an extensive finishing- do not leave too much material. The thinner the workpiece, the easier it bends without breaking.
• If the amount of work is small, then it is better not to cut out blanks, but to prick them from chocks. So it is possible to avoid cutting the fibers and, as a result, marriage during bending.
• For bending, it is desirable to use lumber with natural moisture. If dry blanks are used, then preference should be given to those that have not been processed in drying chamber, but dried under a canopy - in an atmospheric way.
• After steaming, work with softened wood very quickly, as lignin begins to harden almost immediately, especially in the most vulnerable outer layers of solid wood. Usually you need to focus on a margin of time from half an hour to 40 minutes, so there is no point in making large cameras if you simply do not have time to install all the material from which into templates.
• Position the material in the steam chamber so that it is the surfaces facing the outer radius that are unobstructed by the steam jets.
• To save time, many carpenters forgo the use of clamp templates. Instead, they use metal staples and wedges, or limit posts, on the templates.
• Keep in mind that a curved bar or rail will still tend to straighten. And this straightening always occurs by a few percent. So when required high accuracy in the manufacture of the part, it is necessary to conduct tests and, based on the results obtained, correct the shape of the template (reduce the radius).
• After cooling the part in the form, let it stand for a while. Some experienced furniture makers prefer to make an exposure of 5-7 days. The tire, as a rule, is left fixed to the part for all this time.

If there is a need to develop a curved element from wood, then most likely you will encounter a number of difficulties. At first glance, it will seem that it will be easier to cut the required element in a curved form, however, in this embodiment, the wood fibers will be cut and weaken the reliability of the part. Plus, when performing, a very large consumption of material comes out.

Stages of work on bending the board at home:

Wood is cellulose fibers bound together by lignin. Placing the fibers in a straight line affects the flexibility of the wood material.

Tip: a durable and reliable wood material for the manufacture of all kinds of products can only come out under the conditions that the wood is perfectly dried. However, changing the shape of a dry wood blank is a rather laborious process, since dry wood can easily break.

Having studied the technology of wood bending, including its basic physical properties of wood, allowing it to change its shape, it is quite possible to bend wood material in artisanal conditions.

Specifics of working with wood

Bending of wood material is accompanied by its deformation, stretching of the outer layers and compression of the inner ones. It happens that the tensile force leads to rupture of the outer fibers. This can be prevented if a preliminary hydrothermal finishing is carried out.

Can bend timber blanks made of glued wood and solid wood. Plus, to give the desired shape, peeled and sliced ​​veneer is used. Hardwood is considered the most plastic. Which includes beech, birch, hornbeam, ash, maple, oak, linden, poplar and alder. Glued bent blanks are best made from birch veneer. It should be noted that in the total volume of such blanks, about 60% falls on birch veneer.

By production technology bent wood, when steaming the workpiece, its ability to compress significantly increases, and specifically by a third, while the possibility of stretching increases by only a few percent. As a result, one cannot even think about bend the tree is thicker than 2 cm.

how bend board in artisanal conditions: heating in the steam box

First of all, you need to prepare a steam box, which can be made with my own hands. Its main task is to restrain the tree, which is required bend. It must have a hole that is designed to let steam out. Otherwise, under pressure, an explosion may occur.

This hole should be in the bottom of the box. Plus, in the box, you need to calculate a removable cover through which you can remove the bent wood as soon as it gets the desired shape. In order to hold the bent wood blank in the required shape, special clamps have to be used. They can be done without outside help made of wood or purchased at a building materials store.

Several round cuts are made from wood. Holes are drilled in them, offset from the center. After that, you should push the bolts through them, and then drill another one through the sides to push them firmly. Such simple crafts can perfectly play the role of clamps.

Now you can start steaming the tree. To do this, you need to close the wood blank in the steam box and take care of the heat source. For every 2.5 cm of product thickness, the time spent on steaming will be about an hour. After it expires, the tree should be removed from the box and given the desired shape by bending. The process should be carried out quickly enough, and the bending itself should be soft and gentle.

Tip: due to the different degree of flexibility, some types of wood will bend more easily than others. Any methods require the application of various amounts of force.

As soon as the desired result is achieved, the bent workpiece must be fixed in this position. The fastening of the tree is possible during the development of its new form, making it easier to control the process.

how bend board in artisanal conditions with chemical impregnation

Since lignin is responsible for the stability of wood, its bonds with the fibers should be destroyed. This is achieved by a chemical method, and it is quite possible to do this in artisanal conditions. The most optimal for such purposes is ammonia. The workpiece is soaked in a 25% aqueous solution of ammonia, which greatly increases its plasticity. The same way there will be an opportunity bend, twist it or squeeze out some relief forms under pressure.

Tip: you should look at the fact that ammonia is dangerous! Due to this, while working with it, it is necessary to strictly adhere to all safety regulations. Wood soaking must be carried out in a tightly closed container, which is located in a well-ventilated area.

The longer the wood is soaked in an ammonia solution, the more plastic it will become later. After soaking the workpiece and developing its new shape, it is necessary to leave it in a similar curved form. This is necessary not only to fix the form, but also to evaporate the ammonia. However, it is necessary to leave a bent tree in a ventilated area. It is noteworthy that when the ammonia has weathered, the fibers of the tree will acquire the same reliability as before, which will enable the workpiece to hold its own shape!

how bend board in artisanal conditions: bundle method

First you need to make a harvest of wood, which will later be prone to bending. It is very, very important that the boards are slightly longer than the length of the required part. This can be explained by the fact that the bend tames the lamellae. Before you start cutting, you will need to draw a diagonal line with a pencil. This must be done across the underside of the workpiece, which will make it possible, after moving the lamellas, to save their order.

The boards must be cut with a straight edge, and not at all with the front side. Similarly, they can be put together with the smallest change. The cork layer is applied to the mold, which can help avoid any unevenness in the shape of the saw and allow for a more even bend. Plus, the cork will hold back the delamination in the form. After that, glue is applied to the upper side of one of the lamellas with a roller.

It is best to use urea-formaldehyde glue, consisting of 2 parts. It has a high level of adhesion, but dries for a long time. You can also use an epoxy-based resin, but such a composition will cost decent money, and absolutely not everyone can give it to themselves. A typical version of glue for wood in this version is not suitable. Although it will dry quickly, it is considered too soft, which is not at all welcome in this version.

A product made of bent wood must fit into the mold as soon as possible. So, on a lamella smeared with glue, another one lies down. The process must be repeated until the bent workpiece receives required thickness. Boards are fixed together. After the glue has completely dried, it is necessary to make it shorter to the required length.

how bend board in artisanal conditions: propyl

The prepared wood cut needs to be sawn through. Cuts are calculated for 2/3 of the thickness of the workpiece. They must be inside the bend. You need to be very careful, as rough cuts can be difficult to deform the tree, and completely break.

Tip: The key to success when cutting is to keep the distance between the cuts as even as possible. The best option 1.25 cm.

The cuts are made across the pattern of the wood. After you need to compress the edges of the workpiece, which will make it possible to combine the resulting cracks into a single whole. This shape and gets a bend at the end of the work. After which it is corrected. In many cases, the outer side is finished with veneer, less often with laminate. This action will give you the opportunity to correct the bend and hide almost any imperfections made in the manufacture. Gaps in a bent tree are hidden quite easily - for this, sawdust and glue are mixed, after which the gaps are filled with the mixture.

Regardless of the fold option, as soon as the workpiece is taken out of the mold, the fold will relax a little. In view of this, it must be made slightly larger in order to compensate for this effect later. The sawing method is used when bending a corner made of metal or part of a box.

So, using these tips, you can big problems bend wood with your own hands.

When bending wood, there are many things to consider: fresh wood is best suited for this business, it takes a certain amount of time to steam the wood, which depends on its thickness.

Processes for changing the properties of wood to meet requests: technology and properties Wood is a natural polymeric composite material that changes its properties under mechanical and chemical action. Knowing the patterns of material change, it is possible to create them purposefully, giving the qualities required by the consumer. This is called the wood modification process. It is necessary when chipboard production, MDF, OSB, WPC and other wood-based materials, where chopped wood mixed with a polymer binder is pressed to obtain a homogeneous material of standard sizes.
The proposed wood modification technology changes the properties of wood in the array, that is, to the entire depth of the processed material, without resorting to its grinding. This is achieved by the fact that the molecules of the modifier, i.e., the substance that contributes to changing the properties of wood, are comparable in size to the molecules of the wood substance and less than the size of the intercellular spaces in it. Therefore, by means of diffusion or forced impregnation under pressure, the modifier penetrates the entire thickness of the impregnated product, and then, under the influence of temperature and pressure, reacts with natural chemicals found in the wood substance.

Thus, the technology allows not to grind wood, not to use expensive polymer binders, and to achieve the same effect that was achieved with MDF production, for example, but in a cheaper way. At the same time, it is preserved with all its positive properties, the texture stands out brighter, you can change the color (no lamination is required).
So, the modifier in the dissolved state must penetrate into the cellular, be chemically active for the components that make up the wood substance, and, reacting with these components, purposefully change the physical and operational properties of the material. The most suitable substance for this is urea, because in the previously mentioned MDF or OSB, the most applicable binders are carbamide. Carbamide is soluble in water, including that contained in a bound state in wood, which means that by impregnating wood with an aqueous solution of urea, we, paradoxically, “dry” it, “taking” part of the wood moisture on hydrophilic urea. Carbamide or urea actively reacts with such components of the wood substance as lignin, hemicelluloses, and extractives.
And since the polycondensation reaction occurs in the macromolecules of the wood substance, the wood mass acquires new useful qualities specified by the manufacturer, while retaining the positive old ones. The solution of carbamide is not harmful, chemically neutral, moreover - urea grade A according to GOST 6691-77 is used as a feed additive for livestock. Urea-modified wood is certified (GOST 24329-80) and is mainly used under the trademark "Destam" or "Lignoferum" in the production of bearing shells. In the production of building and joinery products, thermally modified wood is also currently used, the technology of which is similar to the proposed one, except that the chemical modification of the wood substance is carried out in the absence of carbamide due to the polycondensation of the decomposition products of lignin, hemicelluloses, extractives and xylans.
Due to thermal degradation, the physical and mechanical properties of thermally modified wood are partially reduced. The technological process for the production of mechanochemically modified wood consists in the impregnation of the original wood of any species and any humidity with a modifier solution. Impregnation can be carried out by the method of "hot-cold baths" - diffusion or in an autoclave - forced. Then drying is carried out, if necessary - with compaction (pressing), and heat treatment, which fixes the new properties of wood. It should be noted that it is more economical to use low-value breeds, since their operational properties after modification are superior to those of expensive breeds.

How to bend wood correctly and in what way?

Manufacturers are currently wooden products they prefer to do without this operation, and if they use bent elements, then from plywood. It's easier to bend plywood. It should be noted, however, that furniture makers natural wood have long ceased to pamper the buyer. All furniture is made of wood or fiberboard. Products made of bent wood, whether it be a chair or something else, are without a doubt stronger, lighter and more elegant.

Choice of wood

The success of bending largely depends on the type of wood chosen. Almost any breed can be bent, but elm, oak, beech, have the best flexibility. If carefully dried wood is needed for carpentry work, then in our case it is better to use freshly harvested wood. Do not take old (by age) wood. The younger the tree, the more flexible it is. From the desired breed, you need to choose pieces without cracks, without knots. At the very least, knots should not be in the place of the intended bend. It is important that the wood is straight-grained, without strands, cross-layers and “screws”. It is best to prepare not sawn boards and beams, but solid round timber.

Making a workpiece

Blanks for bending wooden elements are best obtained not by sawing, but by splitting round timber. The direction of the split should be along the chords of the circle in order to exclude a fragile and unsuitable for bending core. Wooden blocks and planks prepared in this way will not flake during bending. The future part is marked so that the direction of the bend coincides with the radius of the round timber from which the workpiece was chipped off, and the outer side of the bend coincides with the outer part of the former round timber. Chipped workpieces are processed with planers to the right sizes with a small allowance for finishing.

Steaming the workpiece

To give the workpiece the best plasticity, it must be steamed. To do this, you need a metal container of a certain size. In it, the blanks will be “steamed” in their entirety or only in the place of the bend. The second is preferable, since it is more convenient to take the workpiece simply with your hands (without devices), which you cannot do if the workpiece is all steamed.

If a this species works are supposed to be put on stream, then it is possible to make a special metal container with a sealed lid and two holes for placing the bent part inside the “steam room”. This whole simple structure must be tightly closed in order to reduce the release of steam to the outside. Place a rubber gasket under the cover. It is impossible to screw tightly, swelling or even an explosion under steam pressure can occur. A sufficiently heavy cover will ensure tightness and at the same time act as a safety valve in case of excessive pressure increase.

It is difficult to specify the time for complete steaming. It depends on the type of wood, the section of the blanks, the degree of dryness of the blanks. Just from time to time you need to take out the workpiece and try it for bending. The readiness of the workpiece will be felt immediately by bending compliance.

Workpiece bending

It is best to bend the workpiece in a template. The blank, bent and dried in the template, will provide the part configuration we need. Especially if you need not one, but several completely identical parts.

With a certain skill, you can do the same as a shower for a horse harness is made - the steamed blank is bent and the ends are tied with a rope. In this form, leave until completely dry. It is necessary to dry bent parts in a ventilated place protected from the sun. Attempting to artificially accelerate drying by heating can lead to cracking of the wood.

It should be noted that after removing the part from the template, it “loses” a little, i.e. straightens up. Given this property, the blanks must be bent a little “cooler” so that the desired shape is obtained upon release. How much "cooler" is a matter of experience. Much depends on the section of the workpiece, the type of wood, the degree of its steaming before flexible.

Press for bending wood materials

Manufacturer ORMA, Italy

Purpose
This equipment is designed for bending (bending) wood materials. Before bending, the blanks are steamed in specialized chambers. Stabilization of the workpiece is carried out by high frequency current.
This equipment has found wide application in the manufacture of chairs, sledges, school furniture.

Specifications:

The complete bending kit includes
- Steaming chamber - a reservoir for moistening blanks with a condensate collector, complete with a steam generator (a separate generator for each autoclave)
- Pre-bending press (required depending on tasks and performance)
- Bending and stabilization press (selected depending on the tasks and productivity), depending on the complexity of the product, it can be equipped with additional side cylinders. The possible total force is vibrated from 30 to 120 tons. Specific pressure up to 7.5 kg/cm2
- Electronic frequency generator - with the ability to work on two presses for bending and stabilization

Norms and structural strength of bent wood

In addition to the traditional use of bent, building structural elements made in this way are increasingly being used today. The use of load-bearing elements made of bent wood allows you to create new interesting views architectural solutions, which, combined with optimal economic indicators such structures explains the increased interest in them from the side practical application not only in industrial, but also in private housing construction.

There are two ways to make a curved structure from bent wood: sawing it out of boards, bending timber (solid bent products) or layers of wood with their simultaneous gluing (curved glued products). The process of bending wood is based on its ability under certain conditions under the influence of external loads to change its shape and keep it in the future.

It is clear that to cut a product from the board large sizes and curvature is almost impossible, therefore, in order to make a bent board or beam at home for building a beautiful or a dome crowning a decorative turret at home, you should prepare everything you need for bending wood. Just as site optimization allows you to increase the rating of an Internet resource, choosing a quality material for bending improves its result. As blanks, an unedged board or timber without knots is selected, with an oblique layer of not more than 10% of the surface area. The best varieties woods with increased plasticity are hornbeam, maple, beech, oak, ash and elm.

After the material is selected, it is possible to start the bending process, the main stages of which are: hydrothermal treatment, blank bending and product drying. Optimal parameters, at which the bending takes place with the highest quality, are the moisture content of the wood in the range of 25-30% and the temperature in the center of the workpiece from 80 to 90 ° C.

Professional promotion of sites dedicated to the intricacies of wood bending technology will surely arouse the interest of a wide audience, since the simplicity of this process is incomparable with the result obtained. Hydrothermal consists in steaming or boiling the workpiece in hot water.

Steaming is technically more difficult, so at home it is easier to organize the boiling of wood in a cooking tank of a suitable size. The workpiece removed from the brewing tank should immediately be secured to the rail with clamps while the wood is warm. Otherwise, stresses will arise in its outer layers, leading to cracks.

Flexible plywood and its application

Flexible plywood (plywood for bending) is now in great demand, due to the fact that it is a convenient material for the manufacture of structures that require rounding. The use of such bending plywood is effective and expedient, since it takes any necessary shape. Its flexibility allows you to embody the wildest fantasies of designers and produce the most fashionable and modern furniture whether it's an original design wardrobe for your living room, cute shelves for your kitchen or modern and comfortable office furniture.
Such plywood is made from tropical trees, mainly from CEIBA wood, but sometimes flexible plywood is also made from other woods: Parika, Keruing. Flexible (bending) plywood is, as a rule, a 3-layer board, which is glued together in the transverse or longitudinal versions of the jackets.

Flexible plywood, can be used for all types of bends, even very small radii. It does not need to be heated and treated with water. The self-supporting construction of the bending plywood makes the use of structural and special supports unnecessary. Unique design patterns, rounded designs and complex multi-radius shapes that cannot be created from traditional materials are made quickly and easily. Flexible plywood fulfills almost all thickness requirements by increasing the number of layers of material (for example, increasing the thickness to 10mm, 15mm, 16mm, 18mm, 20mm, etc.). Thicker sheets can be obtained by gluing several sheets of thinner bending plywood together.

Tropical high quality plywood is a combination modern technologies and traditional materials. A product designed to satisfy the most sophisticated needs of modern furniture and joinery manufacturers. Flexible plywood (bending plywood) is cheaper than pre-made wood molds. Significant time savings, less labor intensity and greater profitability - these are its advantages over any other way to change the shape of plywood.

In addition to flexible plywood, our company offers another unique product - Ultralight plywood. The range of use of this plywood is also quite wide: it is the production of door panels, the production of cabinet furniture, sofas, armchairs, shelves. Ultralight plywood is a new product on our market, it is 1.8 times lighter than birch. This plywood is well veneered with veneer, finished with films and varnishes, and most importantly, it allows you to significantly reduce the weight of the finished product!

Specifications

Direction of bend Across the grain: along the width

Composition Hot pressed tropical wood with thermal setting adhesive

Density 300-400 kg/cu.m.

Thickness 5mm, 8mm, etc.

Dimensions 2500/2440 mm x 1220 mm etc. order

Bending radius For 5 mm thick, min. 7 cm for 8 mm thick min. 10 cm

Elasticity
Perpendicular to fibers: 210 N/mm2
Parallel to fibers: 6300 N/mm2
(For 5mm panel at 10% humidity)

Store panels horizontally in a clean, shady, dry area.

Apply glue to the panels, fixing the desired shape. After the glue dries, the panel will retain its shape. H.P.L. or the plywood can be glued either during the initial molding or in a separate, final step.

You can use any wood glue.

Panels must be transported on a hard, flat surface. Individual panels can be rolled up, but they should not be stored in this position for long periods of time.

Bending is widely used in industries such as shipbuilding. To begin with, there are a few basic rules that are always respected.

By steaming the wood to bend it, you soften the hemicellulose. Cellulose, on the other hand, is a polymer that behaves like resins - thermoplastics. (Thanks to John McKenzie for the last two suggestions).

To do this, you need heat and steam at the same time. In Asia, people bend wood and just over a fire, but that wood is definitely quite wet - usually freshly cut. Shipbuilders in ancient Scandinavia harvested materials for plating their ships and put them in a salt water swamp to keep them flexible until they needed to be put to work. However, we are not always able to obtain freshly harvested wood for this purpose, and excellent results can be achieved using ordinary air-dried wood. It would be very good if, a few days before the operation itself, you immerse the workpieces in water so that they gain moisture - those Vikings knew what they were doing. You need warmth and you need moisture.

The main rule is about steaming time: one hour for every inch of wood thickness.

Be aware that along with the probability of understeaming the workpiece, there is also the possibility of oversteaming it. If you have steamed an inch board for an hour and it cracked when you tried to bend it, you should not conclude that there was not enough time. There are other influencing factors that explain this, but we will return to them later. Longer steaming of the same workpiece will not give a positive result. It is not bad in such a situation to have a workpiece of the same thickness as that intended for bending and which is not a pity. Preferably from the same board. It is necessary to steam them together and after the supposedly necessary time to get a test sample and try to bend it into shape. If it crackles, then let the main workpiece steam for another ten minutes. But no more.

Wood:

As a rule, the best option will be if you can find freshly cut wood. I understand that the carpenters-carpenters will shudder at these words. But the fact remains that fresh wood bends better than dry wood. You can take a two-meter inch board from white oak, clamp one end of it in a workbench and bend it along any necessary curvature - fresh wood is so malleable. However, of course, she will not remain in this state and she will still have to soar.

In shipbuilding, the main evil is rot. If you are concerned about this issue, then take note that the mere fact of steaming fresh wood eliminates its tendency to rot. Therefore, you don’t have to worry - the frames of the boats are usually made from fresh oak bent under steam and do not rot if cared for. It also means that at least blanks for the Windsor chair can be made in this way. But air-dried oak also gives an excellent result.

When selecting wood for bending, one thing should be avoided - the oblique layer. If you try to bend such a workpiece may burst.

Therefore, regarding the moisture content of wood, the rules are as follows:
1.Fresh wood is best.
2. Air-drying wood is the second good option.
3. - the third and very far from the first two options.

If all you have is after the dryer and nothing else to get - well, then you have no choice. But still, if you can get air-dried wood, it will be much better.