One of the ways of processing blanks of joinery is bending. The wooden blanks treated with hot steam are able to bend and, after drying, retain the resulting shape. Such technological process does not present any particular difficulties, but some features of how to bend wood should be considered. You may also be interested in pine stairs, which you can order on the website http://mirdereva.ru/.
Wood fibers are held together by a special substance - lignin, which, under the influence high temperature softens, and after cooling again fastens the fibers. This is the basis for the bending process. It should be borne in mind that wood of different species lends itself to bending in its own way. For bent products, it is best to use oak, beech, birch, yew, cherry, elm. But pine, spruce, cedar, alder should not be used for these purposes.
Work on bent parts begins with the choice of material. The blanks must be straight-grained, the use of wood with curved fibers is not allowed. The prepared material is dried in natural conditions, under sheds, to a moisture content of not more than 20%. But artificially dried wood should not be used for bending, since it lends itself worse to such processing. If you have to use such material, then before bending it must be soaked in water (at least a week). Soaking is also necessary for hardwoods such as oak, ash, beech.
It is best to use a steam chamber to heat the blanks before bending. Such a camera is easy to make at home using plastic pipe suitable sizes and a regular teapot. Parts are placed in a pipe, and steam is supplied from a kettle. The exposure time in the chamber depends on the size of the part and is determined empirically. In this case, you can be guided by the fact that 1 cm of the thickness of the workpiece requires 30-40 minutes of steaming the wood.
In places of bending on the parts, if the design of the product allows it, you can slightly reduce the thickness of the material, chamfer. This will make the bending process easier. Thin workpieces, in the absence of a steam chamber, can be heated over an electric or gas stove.
Before you start bending wood, you need to prepare a form on which the part will be fixed, and clamps for fixing. It should be borne in mind that after the wood has warmed up, there will be very little time to fix the workpiece, no more than 5 minutes. Therefore, everything must be done quickly, but if the part begins to cool, then it should be heated again. Otherwise, you can break the workpiece.
Therefore, it is important to provide such a design of molds and clamps that would allow you to quickly fix the workpiece in the desired position. If the forms are made of wood, then they should not be covered with any protective compounds, paint, varnish. Firstly, they deteriorate from heating, and secondly, they will interfere with the drying of the blanks.
Short blanks are bent on mandrels of a larger radius, and then they are fixed in the mold. This pre-bending reduces the chance that the part will break when the bend is formed. It is necessary to keep the parts in the form until completely dry so that they do not straighten back. This usually takes 6 to 9 days, and is determined empirically.
After releasing the workpiece from the clamps, it must be postponed for a day, and only then proceed to processing and finishing. This is necessary in order to remove residual extensor stresses. The tips are simple, but they will allow you to easily master the process of how to bend wood.
Bending is one of the methods for making beautiful and durable parts from wood, for example for furniture. Home master it is quite possible to master such a technology. A bent part is much stronger than a sawn one, less wood is spent on its manufacture, and one-butt and end cuts are obtained on sawn surfaces, which complicate further processing and finishing of parts.There are three ways of bending wood. One of them - the most famous one - is the preliminary steaming of wood, followed by giving it the required shape in powerful presses. This hot way bending is used mainly in mass production, for example, chairs.
Along with it, especially at home, two other methods of bending wood are practiced, but already in a cold state.
- First - solid wood bending with preliminary incisions along the bend.
- The second is bend gluing, in which a bent part is obtained by pressure in molds from a blank, which is a package of several layers smeared with glue thin stripes wood.
- When bending in the second way - with notches - in the workpiece to a depth of 2/3-3/4 of its thickness, narrow grooves parallel to each other are sawn, after which the workpiece is given the desired shape.
The maximum bending radius depends on the depth of the cuts (and therefore on the thickness of the blanks), the distance between them and the flexibility of the wood. The incisions are made both parallel and perpendicular to the fibers. This work operation is carried out using a crosscut or manual circular saw with guide stop. If there is no special tool, a regular hacksaw for wood is also suitable. The main thing is that the depth of the cuts is the same.
GLUING WITH SIMULTANEOUS BENDING
At wood bending fibers on inside are compressed, and on the outside - stretched. Wood "tolerates" the compression of the fibers relatively easily, especially if it is pre-steamed. Stretching it is almost impossible.
Flexibility also depends on the type of wood and the thickness of the workpieces. For example, hardwood from moderate climatic zones- beech, oak, ash, elm - easier to bend than tropical tree species(mahogany, teak, sipo, etc.). Conifers are too tough for this.
The resistance value of the bent wood until its destruction is determined by the ratio 1:50, i.e. the bending radius must be at least 50 times the thickness of the workpiece. For example, a workpiece with a thickness of 25 mm requires a radius of at least 1250 mm. The thinner the wood, the easier it bends. Therefore, where possible, it is advisable to make a part of the appropriate shape by bending (Fig. 1).
With this method, individual strips of wood of the same thickness and width are glued, laid in several layers so that their fibers are parallel, and placed in a mold made of hardwood. The matrix and the punch of the mold are compressed with clamps and the package is left in this position until the glue dries.
The thickness of the strips glued together can vary between 1-6 mm, again depending on the required bending radius. Cold curing glue is suitable for gluing the layers. If the bent-glued blanks are intended for use in outdoor structures, it is best to use a waterproof adhesive.
BENDING WITH THE USE OF CLAMPING DEVICES AND PRESS FORMS
To determine the allowable thickness of veneer strips or planks to be bent (larger thicknesses may break the wood), it is necessary to know the smallest bending radius. Most wood is deformed on the inside of the bend. Therefore, it is always necessary to measure here.
As an auxiliary device, it is advisable to use a template that you can make yourself. To determine the bending radius, we take an ordinary school compass and draw several circles on tracing paper (with a slight increase in their radius) that have a common center. As a result, we get a template. We apply it to the surface of the bend, for example, molds and move it until we find a suitable circle largest diameter. Its radius is measured on the template. The resulting value is divided by 50. The quotient of the division will be the maximum allowable thickness of the plank or veneer strip.
When working with molds, the bend on the outside of the workpiece should be smoother than on the inside. In this case, we draw two circles from one center, the radii of which differ by the total thickness of the material of the strips.
The most difficult situation is when it is required to bend a part of a complex configuration with different bending radii. Here, bends for the inside or outside of the workpiece can be built freely if its shape is not tied to the contours of any piece of furniture.
The line for the second cut (the first - at the beginning of the bend) can be built in this case like this. We measure the total thickness of the layers to be glued with a compass, draw a circle with it on hard cardboard, cut out a circle and attach it in several places to the line of the first cut. At the same time, we apply a circle so that it is in contact with the first line, and draw its outline, respectively, on the opposite side. The second cut line will be a through connection between these auxiliary lines.
TECHNOLOGY OF BENDING WITH THE PERFORMANCE OF INSECTIONS ON THE WORKPIECES
When determining the number of notches cut on the workpiece for bending along a known radius (it also depends on the width of the groove and the type of wood), we use an auxiliary structure. To do this, we take a bar similar to the workpiece (Fig. 2). We cut out one single cut on it with a depth of 2/3-3/4 of the thickness of the bar. Draw a straight line on a sheet of paper and mark the point of the incision on it.
We put the bar on the paper so that its lower edge before the notch coincides with the drawn line and the marked point of the notch, and fasten the bar with a clamp to the desktop. We set aside the distance of the required radius b on the line and the bar and bend the bar until the upper edges of the notch close. The distance a between the end of the line and the mark on the bar will be the distance between the individual cuts that can be marked on the workpiece.
If the cuts need to be cut on the outside of the workpiece, the distance between them and, accordingly, their number is determined in the same way. We bend the workpiece as much as the elasticity of the wood allows. If the test piece of wood breaks, then this can be expected from the workpiece fixed in the mold.
According to the materials of the magazine "Do it yourself"
Often during the course of repair work there is a need to obtain curved surfaces of products made of wood. How to bend the board in such a way that the bend is strong and does not crack during the bending process? What if you decide to do overhaul with your own hands, then you should not retreat before such difficulties. In this article, we will talk in detail about how to give wood material curved shape.
How to bend a tree?
No, our task is not at all to bend an innocent plant. It's about wood. building materials. How to bend a tree so that it bends and does not break? Bending method wooden products It has been known since ancient times: to give wood a shape, only heat and moisture are needed, under the influence of which the plasticity of the material increases with all the ensuing consequences. How to bend a tree? Hold him in hot water (the higher the temperature, the faster the processes) or steam ( a steam generator can be built from a kettle or use an iron). The higher the temperature, the faster the wood gives up and you can start bending it. Moistened and heated wood can be bent under the action of the load (the ends of the board are placed on the supports), and the load is placed in the place of the future bend. Dried wood perfectly retains the minimum radius of curvature that was achieved during the bending process. Now we know how to bend a tree, we can dwell on this issue in more detail.
The reaction of wood to external influences
The fact is that wood reacts differently to bending. The convex part is under tension, the concave part is under compression. Moreover, the material also reacts differently to steaming. For example, the ability to compress increases by as much as a third, but to stretch - just a couple percent. That is why it is not worth thinking about how to bend a board more than two centimeters thick at home. It must also be taken into account that different types Woods react differently to bending. For example, such species as oak, larch, maple bend poorly, but beech, ash, walnut - well. So before you think about how to bend the board, decide on the type of wood from which it is made.
How to bend plywood, fiberboard, MDF
At home, plywood is bent by increasing its moisture content, then ironing (an iron is required), and fixing it in a template. Any template can be frame element and it is not at all necessary that its shape should be curvilinear. The product is attached to the template with adhesive tape. You can clamp bent plywood between two spacers, give it a bent shape due to ropes, tying them around the product in several places along the radius of curvature. Plywood can only be used after it has dried. It seems that we figured out how to bend plywood - we move on.
How to bend fiberboard? The technique is the same as in the previous case! How to bend MDF? In this case, you can go in two ways: either bend thin sheets (no more than 5 mm) and glue them together, or use flexible MDF, in which there are transverse slots on one side. The thickness of such sheets is usually 8 mm. When bent, they overlap each other with milled sides, after which they are glued together. That, in fact, is all!
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Nature does not like straight lines and it takes a lot of time and effort to make wood products straight. However, wood bending is also a rather laborious process. bent wooden elements often used in Scandinavian furniture in the form of beautiful, light and durable products with a unity of structure and form. In this article, we will look at several ways to bend wood: simple power bending, kerf bending, pair bending, and layer bending.
This is the simplest method and consists of manually bending the wood and attaching it to a mold to fix the bend. The thinner the wood, the easier it is to bend. It follows from this that the greater the bend, the thinner the wood should be. The veneer can acquire almost any bend, while a 2 cm thick oak blank is almost impossible to bend. It should also be taken into account that different breeds woods have different degrees of flexibility. So the ratio of the thickness of the workpiece and the minimum bending radius for some species will be: beech - 1/2.5; oak - 1/4; birch - 1/5.7; alder - 1/8; spruce - 1/10; pine - 1/11. That is, with a beech blank thickness of 10 mm, the minimum bending radius will be 25 mm.
As a rule, the workpiece is fixed with glue, since the use of nails or screws in the bends can lead to cracks and breaks. There is an unspoken rule - what can be fixed by hand can also be fixed with glue. When gluing, to reduce gaps, you need to move from the center to the edges, or from one edge to the other.
This method of bending wood is the least durable, since the wood is sawn through almost its entire thickness and there is very little strength left in it. Therefore, this method of bending wood is used only where there is no heavy load, such as rounded corners, etc.
The main material for the manufacture of bent sawn parts is plywood. For achievement best results cuts are best made on circular saw using a limit stop. Cuts should be made across the fibers at a distance of about 5-10 mm. from each other. The depth of cut should be about 1/5 of the thickness of the workpiece.
To fix the bend, you can use glue or wood filler. By gluing and fixing two curved slats with cuts inward, you can create interesting elements in some designs, albeit with limited strength.
By their own physical properties such wood is close to hydrothermally bent wood, and according to some indicators of dynamic loads, it has even better mechanical properties than solid wood.
The first step is to prepare the slats. The thickness of the lamellas is largely determined by the magnitude of the bend. The greater the bend, the thinner the lamellas should be and vice versa. As a rule, the thickness of the lamellas should not exceed 3.2 mm.
Then the cut layers of wood are smeared with glue and compressed in a template using grippers. To connect the lamellas, you cannot use ordinary carpentry glue. For these purposes, adhesives based on urea-formaldehyde or epoxy resins are best suited.
Before removing the part from the template, the glue should set for a day. It should also be borne in mind that after unclenching the mold, the workpiece may straighten a little. This effect can be minimized by reducing the thickness of the lamellas or creating a shape with a slight inflection.
Hydrothermal bending of wood gives the highest quality result, but requires a lot of labor and technical equipment.
Before starting the bending process, due attention should be paid to the choice of wood. Almost any type of wood can be bent, but hardwoods such as oak, beech, elm, birch, cherry, maple, walnut, ash have the best flexibility. It is not recommended to use coniferous and soft woods such as spruce, pine, cedar, alder. It is also important that the wood is free from cracks and knots at the intended bend.
Each cell of wood fibers is covered with lignin - glue-like chemical, which at ordinary temperature firmly binds the fibers. The heat transferred from the steam softens the lignin, allowing the fibers to contract and stretch. As the lignin cools, it hardens and binds the fibers together again.
Freshly cut wood is best suited for bending. The best option atmospheric drying wood is also, since during chamber drying, lignin is noticeably hardened, making it difficult to bend. Before steaming, kiln-dried wood can be soaked overnight in water. Atmospheric wood and pre-soaked kiln-dried wood require the same processing time.
Wood acquires the best plastic properties at a moisture content of 25-30% and at a temperature of about 100°C. Steaming time depends on the thickness of the wood. So, for example, for steaming a workpiece with an initial moisture content of 30% and a thickness of 25 mm to reach a temperature in the center of the workpiece up to 100 ° C, 1 hour is needed, and about 2 hours with a thickness of 35 mm.
Before removing the workpiece, make sure that all tools are at hand, as the wood cools and hardens very quickly. Be sure to wear thick gloves to avoid getting burned by the steam. Remove the part and immediately fix it with grippers.
The removal of the product from the mold is usually accompanied by a slight extension. Therefore, the shape should have a bend a little more than required in order to maintain the desired curvature of the product. To minimize buckling, leave the piece fixed in the mold for at least a few days.
How to bend a board, plywood, fiberboard, MDF with your own hands
Often in the process of carrying out repair work, it becomes necessary to obtain curved surfaces of products made of wood. How to bend the board in such a way that the bend is strong and does not crack during the bending process? Well, if you have already decided to do a major overhaul with your own hands, then you should not retreat from such difficulties. In this article, we will talk in detail about how to give a wood material a curved shape.
How to bend a tree?
No, our task is not at all to bend an innocent plant. We are talking about wood building materials. How to bend a tree so that it bends and does not break? The method of bending wooden products has been known since ancient times: to shape wood, you need only heat and moisture, under the influence of which the plasticity of the material increases with all the ensuing consequences. How to bend a tree? Hold it in hot water the higher the temperature, the faster the processes) or steam ( a steam generator can be built from a kettle or use an iron). The higher the temperature, the faster the wood gives up and you can start bending it. Moistened and heated wood can be bent under the action of the load (the ends of the board are placed on the supports), and the load is placed in the place of the future bend. Dried wood perfectly retains the minimum radius of curvature that was achieved during the bending process. Now we know how to bend a tree, we can dwell on this issue in more detail.
The reaction of wood to external influences
The fact is that wood reacts differently to bending. The convex part is under tension, the concave part is under compression. Moreover, the material also reacts differently to steaming. For example, the ability to compress increases by as much as a third, but to stretch - just a couple percent. That is why it is not worth thinking about how to bend a board more than two centimeters thick at home. It should also be taken into account that different types of wood react differently to bending. For example, such species as oak, larch, maple bend poorly, but beech, ash, walnut - well. So before you think about how to bend the board, decide on the type of wood from which it is made.
How to bend plywood, fiberboard, MDF
At home, plywood is bent by increasing its moisture content, then ironing (an iron is required), and fixing it in a template. Any frame element can serve as a template, and its shape does not have to be curvilinear at all. The product is attached to the template with adhesive tape. You can clamp bent plywood between two spacers, give it a bent shape due to ropes, tying them around the product in several places along the radius of curvature. Plywood can only be used after it has dried. It seems that we figured out how to bend plywood - we move on.
How to bend fiberboard? The technique is the same as in the previous case! How to bend MDF? In this case, you can go in two ways: either bend thin sheets (no more than 5 mm) and glue them together, or use flexible MDF. in which on one side there are transverse slots. The thickness of such sheets is usually 8 mm. When bent, they overlap each other with milled sides, after which they are glued together. That, in fact, is all!
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