Sawing oak. Development of technology for cutting oak wood. Oak drying methods: chamber and tubeless methods

Oak is a very popular material that is widely used:

• Construction.
• Finishing work.
• Furniture creation.
• Manufacturing of art objects and souvenirs.

Naturally, not just cut and sawn wood is used, but also processed and high-quality dried material. This is a prerequisite in order to avoid cracking, changes in the shape and dimensions of the product in the future. An oak that is used in construction or furniture must have certain physical and mechanical properties.

Therefore, when the sawing is completed, the question arises: “ How to dry oak properly". We will give the answer to it in this article.

Features of oak wood: what should be the result of drying

Oak lumber is quite capricious, it is difficult to dry naturally. It is not enough just to leave the stack under a canopy or in the open sun in order to get the desired result after a certain time.

Before how to dry oak boards, it is necessary to understand the features of the material:

• Oak wood is susceptible to dryness. This means that when the moisture level falls below the critical mark, internal and external cracks can form.
• The most difficult thing to dry is freshly sawn oak, the moisture content of which exceeds 25%.
• Temperatures above 55 degrees are unacceptable at the initial stages of drying. This leads to the collapse of the woody capillaries, that is, to the appearance of multiple internal cracks.
• It is not recommended to send freshly sawn material with a moisture content of more than 40% for drying.
• Proper drying of oak requires maintaining a certain level of temperature and humidity.

Features of drying oak wood are such that in order to obtain a high-quality material without defects with a certain percentage of moisture, it is necessary to draw up a preliminary plan for this procedure, use special means.
There are several tasks for drying oak:

• Shrinkage with prevention of changes in linear dimensions. Here the humidity is reduced by up to 30%.
• Drying to transport moisture content of 20-22%.
• Full volume dryer for direct use. The humidity level should be 6-12%.

Oak drying methods: chamber and tubeless methods

From the foregoing, it is obvious that obtaining wood from a freshly felled oak that meets all the necessary parameters is a laborious and time-consuming process.

There are many ways to reduce the moisture content of boards, logs and beams, but they can all be divided into two broad categories:

• Tubeless (atmospheric) drying.
• Chamber drying.

Atmospheric drying is ideally the most affordable and natural way to reduce moisture levels. The technique has been used in sawmills and woodworking industries for centuries. It is believed that naturally dried wood is of the highest quality, it can be used for decades without changing its original qualities. But the method has one significant drawback - the length of time.

Since modern life is very dynamic, buyers are interested in purchasing material as quickly as possible. Logging enterprises, in turn, prefer to sell wood in the shortest possible time. Therefore, in the XIX-XX centuries, many techniques were invented using electrical energy. Chamber drying is carried out in convection chambers, the condensation method and vacuum drying are also used.

All work is carried out in an industrial environment, as a rule, are divided into the following stages:

• Warming up.
• Drying directly.
• Cooling, obtaining a given humidity threshold.

Chamber drying is similar to multiply accelerated atmospheric drying, the required result is achieved many times faster. But the disadvantage is the high cost of the procedure. It is necessary to use expensive equipment, most often this is possible only in an industrial environment.

Fortunately, infrared dryers have appeared not so long ago, which make it possible to shorten the time of atmospheric drying, to obtain the required result in terms comparable to the chamber treatment. At the same time, all features of drying oak wood, the material does not undergo aggressive effects that destroy the structure. At the end of the process, the humidity reaches the required level.

Infrared drying of oak: the advantages of a modern way

Competent drying of oak now it has become possible even at home. Infrared dryers manufactured under the FlexiHIT brand have a cassette form factor, are easily positioned inside stacks, and can also be used for drying small pieces of material. In this case, the volume of wood does not matter, it is enough to use the required number of dryers and position them correctly. The result is achieved in 3-7 days.

The properties of infrared-dried oak correspond to those of atmospheric-dried wood:

• The material has a given moisture content.
• Fibers do not warp, cracks and stressed areas do not form.
• The appearance matches that of naturally dried oak.

It is noteworthy that everyone can use IR dryers; you do not need to have special skills to get the result. The equipment operates on a conventional electrical network, while consuming very little. Drying one cubic meter of wood requires no more than 200-400 kW.

To check the humidity, it is enough to use a moisture meter, when the required indicator is reached, the infrared dryers are turned off. The oak can be used immediately for its intended purpose.

Oak wood is quite capricious when drying, in order to obtain an optimal result in the shortest possible time, it is better to prefer tubeless drying in combination with IR dryers.

DEVELOPMENT OF OAK WOOD SLITTING TECHNOLOGY

Toropov A.S. , Sharapov E.S., Krasnova V.F., Toropov S.A.

(MarSTU, Yoshkar-Ola, RF)

Results of researches new technology of sawing up oak wood with ring defeats are presented.

Among the valuable tree species growing on the European territory of Russia, the English oak ( Quercus robur L .). Its valuable timber is in unlimited demand.

According to the research results of P.M. Verkhunova and I.P. Kurnenkova, the oak forests of the Chuvash Republic are characterized by a large faulty forest stands. In particular, the defect in the structure of wood is very common - the internal sapwood of oak. Internal sapwood is caused by frost damage to the sapwood layers. Internal sapwood differs from the kernel in its lower resistance to decay. At the same time, annular large-pit rot develops in it later (45.1 - 75.0% of forest stands are affected by sulfur-yellow tinder fungus Laetiporus sulphureus L .), then turning into pink - brown prismatic rot, excluding the possibility of using raw materials. Quite often, several areas of annular lesions are found in oak wood (Fig. 1).

Figure 1 - Cross-section of an oak affected by sulfur-yellow tinder fungus

For this reason, oak wood growing on the territory of the Republic of Chuvashia, as a result of sanitary selective felling, is transferred to the category of illiquid. Manufacturers prefer to use expensive imported raw materials from the southern regions of our country, which increases the cost of transport costs, and this entails a significant increase in the cost of finished products.

The technology developed by us allows the rational use of illiquid oak wood with an increase in the quality of the output sawn timber. According to the new cutting method (fig. 2) To Round timber 1, having circular lesions of wood 2, is fixed for a healthy peripheral zone, the shape and parameters of the affected area are determined and subdivided according to the program, thus obtaining sectors 3 with an affected area 2 (division of timber into sectors in the longitudinal direction).

Figure 2 - Method of cutting round timber with circular lesions of wood

Further, the resulting sectors 3 are based on one of the processing surfaces and the affected part is separated in the longitudinal direction along the boundaries of the affected layers parallel to the tangent at the intersection of the generatrix of the timber and the bisector of the sector angle, as a result, the peripheral segment 5, the affected part 4 and the core part 6. The affected parts 4 are unfolded relative to each other by 180 0 in the vertical plane and fastened together, and the core parts 6 are also unfolded by 90 0 in the vertical plane and fastened together. Next, the peripheral segment 5 is cut to obtain high-quality sawn timber. After the workpieces have dried, they can be glued to each other along the edge. In order to increase the strength of the joint in the workpieces, the elements of the joinery are made. In order to obtain sawn timber of various sizes in terms of thickness and quality, the workpieces are sorted according to geometric parameters and quality characteristics.

The use of a new technology for cutting oak wood with ring lesions will make it possible to rationally use the resources of low-quality wood.

Literature

1. Verkhunov, P.M. Variety-forming vices and commodity structure of oak forests in the Middle Volga region [Text] / P.М. Verkhunov, I.P. Kurnenkova // Forest inventory and forest management: Interuniversity. Sat. scientific. tr. - Yoshkar-Ola .: MarSTU, 1997.- S. 72-78.

2. Vakin, A.T. Wood flaws [Text] / А.Т. Vakin, O. I. Poluboyarinov, V.A. Soloviev. - M .: Lesn. prom-st, 1980 .-- 112 p.

3. Alekseev, I.A. Forest commodity science with the basics of wood science [Text] / I.А. Alekseev, O. I. Poluboyarinov. - Yoshkar-Ola .: MarSTU, 2006 .-- 457 p.

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Lumber - wood materials (beams, boards and bars) obtained by sawmilling. Distinguish between radial, tangential and mixed sawn timber. Lumber with sawn edges is called edged, with uncut - unedged.

Large high-quality logs (these are logs from the lower, butt part of the tree) provide the most valuable lumber. When cutting such logs, it is necessary to determine the thickness of the resulting boards in order to maximize the volume and cost of the material obtained. Since the price of lumber depends on its thickness, and in addition, less sawdust is produced when sawing into thick cant, this decision has a serious impact on income. However, if the quality of the thick material is lower, even if the best edge is almost clean, then it will not be easy to sell it for a good price. The sawman should try to reduce the size of the material to be cut when he sees that the quality of the wood begins to decline.

If the log is good, it is at least unwise to produce large lumber and railroad ties from the center of the log. Because the price of a timber is always less than the price of a board.

For tall logs, circular sawing is recommended. In fact, tapering sawing with the log tilted so that the sawing is parallel to the bark is recommended for all “good” edges. The result will be clean wood along its entire length, more valuable pieces of lumber, and this will avoid the need to saw clean wood afterwards into short pieces. When you get to the low-grade part of the log, go to the shape of the log and minimize the trimming operation on the sides.

Sturdy but substandard logs should be cut as quickly as possible. There is little use from these logs - the profit is very small, or none at all, which means that these logs need to be removed from the machine the faster the better. Any sawing method works here. Most often they are sawed into a bar, or they are simply sawed through. In this case, it is generally better to reduce the overturns of the log to absolute zero.

Loose logs provide such a marginal profit and such a huge risk of breaking the product that it is better not to deal with them at all.

Logs of average quality can produce a significant amount of good lumber, and here a lot depends on the sawman, how he turns the log. Here the decision to rotate the log is critical to profit.

First you need to choose the worst part of the log and cut it without taking into account the escape. But you can't cut too much from this side. For small logs, in general, you need to cut one layer, that is, cut once along the entire length of the log, or a layer and a short board, and then turn the log to the opposite side.

Another way is to choose the best side of the log and start sawing taking into account the taper of the log. Then this part is sawn for a long time before the log is turned over.

The lumber is cut from one side until the sawman expects the next board on that side of the log to be as good as the boards that can be cut from the other side. There is an exception: if you start sawing from the worst edge of the log, you have to saw until you get a perfectly smooth cutting surface in order to flip the log onto it. In other words, the good side of the log needs to be cut deeply, and from the bad side, a layer or layer and one board are simply removed.

If we take a log with a diameter of 60 cm, although this is true for all logs of any size, when sawing with a 180 ° turn, we get 8 boards, which need to be additionally cut on the sides, and using a less efficient method, always turning to an adjacent edge, we get 13 such boards. This circumstance alone can already be a significant argument in favor of a 180 ° log turn, especially for small businesses. In addition, this method of sawing produces more wide planks, which are usually more valuable. When flipping to an adjacent edge, 8 tangentially cut boards are obtained, which are subject to strong warping during drying. Further, if it is a walnut or red oak with a narrow sapwood part, then with a 180-degree turnover of the log we get 10 boards with sapwood, with another method of turning over - 13 boards. Sapwood causes drying problems. And with a 180-degree turnover of the log, the internal stress of the wood is relieved, which, as a result, allows you to avoid cracks and cracks.

Turning over to an adjacent edge may be easier, but from an economic point of view and from a sawing safety point of view, it is more beneficial to rotate the log 180 °.

After the two opposite edges of the log have been sawn, you need to move on to the third and fourth. As usual, the worst of these edges is cut first, disregarding the taper of the log. However, a good quality edge should always be cut parallel to the bark to maximize the yield of good lumber from the log.

The width of the first layer when sawing from all four sides of the log is critical.

If the edge is of good quality, that is, the first sawn board can be classified as a good grade, then the minimum width of the sawn timber should be 15-1 cm. Of course, this depends on the size of the log itself. To take into account further processing of the board, planing or even trimming on the sides, 15-1 cm is recommended, and not 15 cm.

If the edge is of poor quality, then it makes sense to saw boards with a width of at least 10-1 cm. The length of such boards should be at least 1.2 m. It is generally necessary to produce boards of no less length on your sawmill.

When it comes to logs of obviously poor quality, it makes sense to saw them from the "belly" or from the "ears", rather than looking for a good edge. The "ears" are usually removed in 1 or 2 saw passes, revealing a smooth surface inside the log. Cutting from the "belly" requires more manipulations, and as a result you get a few short, but clean boards.

The timber has a number of advantages over thin boards. The timber often has a beautiful wood pattern that customers love. When dried, it dries out half as much as boards (3% versus 6% for boards). Less cracking during drying. When the ambient humidity changes, the timber is more stable. When the floor is covered with it, it hardly wears out.

Also, when sawing a bar, the yield of a useful product from a log is 20% lower. Its production rate is much lower. It requires 15% more drying time. The timber dries out in thickness 2 times more than narrow boards. Sharp branches that remain in the timber, in contrast to round branches in boards, greatly reduce the strength of the material.

Radial a cut in which the plane of the cut passes through the core of the trunk. The wood of such boards is quite uniform in color and texture, the inter-ring dimensions are minimal. Radial cut boards are resistant to external influences, practically do not deform and have high wear resistance. A radial cut board has a shrinkage factor of 0.19% and a swelling factor of 0.2%. These figures for radial sawn timber are twice as good as for tangential sawn boards. For a radial cut board, the process of shrinkage and swelling goes along the width of the fibers - the thickness of the board, and for a tangential cut along the width of the board, since the fibers at the "tangent" are located in width. Accordingly, the floorboard, parquet board, imitation of a bar, block house, lining of radial sawing have practically no slots in comparison with similar products of tangential sawing. Since the output of radial cut boards is 10-15% of the total volume, their cost is quite high.

Radial sawing of wood is a method of sawing a log, in which all the fibers in the board go along the direction of the annual rings. With radial sawing, the lumber has the best physical and mechanical properties. The strength and hardness of wood with a radial cut is higher than with a tangential one.

The output of a radial cut board is usually small (no more than 30%). On UP-700 rip saws, the radial board yield reaches 60%. Such a high figure is achieved thanks to the cutting optimization system. Choosing among the optimization criteria the maximum output of the radial board, the conditions of the radial and semi-radial cutting, the technologist determines the percentage of the output of the radial board.

Radial sawing can be done with other equipment. But the percentage of radial board yield on other equipment depends on how the operator cut the log. Usually this figure is significantly less than 50%. Due to the microprocessor control system and the optimization system on the UP-700, it is possible to obtain the maximum possible number of radial cut boards.

Saw texture: 1 - tangential cut; 2 - radial cut; 3 - semi-radial cut.

Tangential is called a cut, in which the plane of the cut passes at a distance from the core, tangentially to the annual layer of the trunk. Such boards have a pronounced texture and a rich wavy pattern of annual rings. Tangential sawn boards have higher shrinkage and swelling rates, but are more affordable.

Sawing hardwood

The sawing operation includes decisions about board thickness, log flipping and log taper compensation. It depends on many factors: on the type of wood, the quality of the log, its size, the design of the machine and the grade of lumber that needs to be obtained. There are 3 standard cutting patterns:

Simple sawing

The log is sawn until its core is exposed, and then flipped 180 ° and finished to the end. This is the quickest and easiest sawing method, yet this method requires each piece of lumber to be cut off the sides. The lumber cut in this way is somewhat wider and heavier, of lower quality and has a lot of waste. It is extremely prone to warping during drying. Therefore, simple sawing or sawing through is justified only in the case of logs of very low quality, when all the above disadvantages are no longer particularly important.

Circular sawing

When sawing in a circle, a cut is made first, and the log is turned over to a new edge, sawed, and turned over again, until at least 5 turns occur. From a financial point of view, this is the best way for medium to high quality logs, although at the same time it is difficult to carry out such a turn of a log on some sawmills, and the daily productivity will be low. Of course, a hydraulic machine solves this problem.

Sawing timber

Sawing cant maximizes the sawmill's productivity (number of boards per day) and is typically used in the industry for medium to large sized logs. In this case, the log is first sawn as when sawing in a circle, but the central part of the log, which can have dimensions of 18x23 or 25x25, and so on, is either transferred to another machine for processing along the processing line, or is sold as a large and heavy bar. Basically, in this way, logs of medium and low quality are cut, when it is impossible to get valuable lumber from the central part of the log. This saves time and effort in producing a product that is not very high quality and therefore not very expensive.

Deciding which side of the log to start sawing, which cutting surface to open first, is the most important part of sawing. We divide the log into 4 faces, each of which extends along the entire length of the log and occupies a certain part of its circumference. The choice of the first face is determined by the position of all the others.

When sawing in a circle and sawing a bar, two basic rules apply:

The worst edge of the log is cut first without considering the taper of the log. Log tracking means raising or tilting the log so that the saw cuts parallel to the bark. Since this is the worst part of the log, this means that it will make short boards and a lot of slabs. Since we do not take into account the taper of the log, this gives us the opportunity to cut parallel to the bark from the opposite, better side of the log, without lifting or tilting the log. This means that more high quality boards will come out of this best part of the log, moreover, the same length as the length of the log.

Saw the best edge of the tree first, taking into account the taper of the log. This means that the log must be lifted or tilted so that the first cut is made parallel to the bark.

The end result of both methods will be roughly the same, but the second method has one advantage. In this case, it is easier for the sawman to rotate the log, because the open edge is the cleanest, there are no defects on it. In the case of the first rule, the best part of the tree is the part opposite to the open face. It is not visible, and it is impossible to precisely rotate the log. Usually, if the wood is of good quality, then both rules work in much the same way. But when faced with a worse log, it is better to use the second rule.

Sawing soft wood

Many of the methods used when sawing hardwood are also suitable for soft varieties. But there are also some differences. Of course, safety considerations must prevail over the desire to produce as much product as possible.

Position the log so that, when cutting, minor material defects are inside the lumber, of course, if these defects are not so serious as to affect the strength of the final product. If possible, cut so that all branches and defects are on one side of the lumber, while the other side is clean. However, in the case of building materials, the clean surface does not affect the final price of the product. But large branches or defects can affect the strength of the structure.

Choose the worst side of the log and start sawing from there, producing short lumber. The first lumber will be the worst and therefore must be short to be sold.

After the log has been cut from a bad edge along the entire length of the log, go to the opposite edge and cut parallel to the bark. With a good edge, the width of the board to be sawn should be at least 15 cm. On smaller logs, less than 30 cm in diameter, the first board should be 10 cm wide. Huge logs will have fewer defects inside and therefore do not need to be transferred to large building structures.

You should always flip the log from one side to the other if the lumber from the new side is of better quality than the one you just sawed.

Waste logs. It is necessary to cut the "ears" in one sawing pass, then turn the log over to the "belly", perhaps you can make at least a few short boards out of it.