For many centuries, humanity has been using wood as a building material and, despite the constant emergence of new ones, modern materials, popularity natural wood does not decrease at all.
How to choose the right lumber from a huge assortment? What causes the differences in price and quality?
Quality finished materials made from wood depends on many parameters - the type of wood and the quality of the original timber, the professionalism of the machine operators, compliance with the technology of drying lumber and the production of finished products. Another factor that has a significant impact on the quality and appearance lumber, as well as their mechanical properties, is the method of cutting wood that determines the texture of the board.
There are several types of wood cutting - tangential, radial, rustic and transverse, of which the first two are most widespread. To understand the difference between types of cuts, you need to have a good knowledge of the structure of wood and understand the technology of sawing wood.
In cross-cutting, wood is cut across the grain. The method is used in production artistic parquet. A rustic cut is any cut made at an acute angle to the direction of the grain. The method is used in the production of lumber for rustic flooring - the most heterogeneous and original in pattern and shade.
With a tangential cut, the cut plane runs tangentially to the annual layers of the tree at some distance from the core. Since wood fibers, as a rule, do not have a single direction, they create natural patterns on the surface of the board in the form of fancy “arches”, “curls”, “rings”. The texture of the resulting tangential cut board is uneven and may contain wood pores. Some of the dry boards may develop delaminations on the surface after finishing planing. After tangential sawing, boards are characterized by higher coefficients of shrinkage and swelling; moreover, such a log sawing scheme allows you to increase the coefficient useful output, which in turn leads to a reduction in the cost of the board.
For radial cutting of wood, the cutting plane is located perpendicular to the annual rings. With this method, the texture of the board is quite uniform with minimum distance between annual layers. This not only creates beautiful drawing, but also helps to increase the strength of lumber.
Radial cut boards have good resistance to external influences, have greater resistance to deformation and wear resistance than tangential cut boards.
The shrinkage and swelling coefficients of radially cut lumber are 0.18% and 0.2%, respectively, which is almost two times better than that of tangentially cut lumber. The reason for this phenomenon is that for radial cut boards, shrinkage and swelling occur along the thickness of the material, in contrast to tangential cut boards, in which dimensional changes occur along the width of the board. This explains the fact that in finished products (parquet boards, floor boards, block houses, imitation timber, lining) made from radially cut lumber, there are almost no gaps on the front surface, which is not excluded in products made from tangentially cut lumber. To obtain laminated veneer lumber by splicing wood without knots, blanks and boards of radial and semi-radial cuts are used, since the mechanical and geometric characteristics of the timber depend on the resistance of the fibers, which increases when gluing layers with multidirectional annual rings with an inclination angle of up to 45°.
The average useful yield of radial cut boards is only 10-15%. This explains their high cost. Radial cutting includes lamellas in which the angle between the annual rings and the blade is 60-90°. If the specified angle is in the range of 45-60°, such boards are classified as semi-radial cut. The best performance qualities has lumber in which the angle between the annual layers and the cutting plane is 80-90 degrees. Taking into account semi-radial cut boards, the useful yield coefficient can reach 30%.
Usually, when radial sawing The log is initially sawn into quarters, and then boards are sawn off from each quarter, alternately from two layers. For sawing logs in a radial way, for example, UP-700 longitudinal sawing machines can be used. Important has a microprocessor control and optimization system UP-700, which is used by technologists to determine the percentage of yield of radial cut boards based on the criteria for optimizing the maximum yield finished products, as well as the conditions of radial and semi-radial cutting.
Comparing radial and tangential types of cuts, several conclusions can be drawn:
- Radial lumber has best properties shrinkage and swelling.
- Radial cut boards have the best mechanical characteristics and stability of geometric dimensions.
- The wood of radial cut boards has a uniform shade and uniform texture, which gives special decorative value finished products made of wood.
- Due to their characteristics, radial boards are more widely used, although they have a higher price.
You probably noticed that parquet boards have different pattern on a cut: in even strips or randomly, with a large number of lines and circles.
Radial cutting of wood - elite boards for select parquet
To get that same “striped” pattern, the log is sawn strictly along the radius. But radial cutting produces a lot of waste, so ready-made boards rise in price. In addition, the wood is less porous and therefore more wear-resistant, which also affects the cost. That's why radial cutting is considered elite.
Tangential cutting of wood - ordinary parquet boards
In production regular board the cutting plane runs at a distance from the center tangentially to the growth rings. This way you get more boards from one log, but the pattern will be unpredictable, with a lot of curls, lines, spots and rings. Wood looks more natural. Unlike radial cut boards, in this case the wood is more porous and less resistant to wear. Therefore, tangential cut parquet belongs to the economy class.
Thanks to modern technologies production, as well as special compounds for impregnation of parquet, the durability of tangentially cut wood increases.
Wood defects- These are natural deficiencies of individual sections of wood, reducing its quality and limiting its use.
Defects are the defects of wood of mechanical origin that arise in it during the process of harvesting, transportation, sorting, stacking and mechanical processing.
One of the wood defects is fiber inclination- used to be called cross-layer. As is already clear from the name, this defect consists in the deviation of the fibers from the longitudinal axis of the trunk. The inclination of the fibers can be either tangential or radial.
Traction wood characterized by a change in structure in the extended zone of trunks and branches, manifested in a sharp increase in the width of the annual layers. Under the influence of light, such areas of wood are colored Brown color. As a rule, traction wood is typical for hardwood trees.
Curlyness- tortuous or random arrangement of wood fibers. Occurs in everyone tree species, more often in deciduous trees.
Curl- local curvature of annual layers near knots or shoots. It can be one-sided or through, reducing the strength of wood. The same " side effects"They also give ocelli - traces of dormant buds that have not developed into shoots. Their diameter does not exceed 5 mm. The ocelli are scattered and grouped, light and dark.
Pocket- density within or between annual layers, filled with resin or gums.
Core- a narrow central part of the trunk, consisting of loose tissue of brown or lighter color than the surrounding wood. At the ends of the assortment there are spots of about 5mm various shapes, on the radial surface - in the form of a narrow strip.
Displaced core- eccentric location of the core, accompanied by curliness.
Double core- the presence in the assortment of 2 or more cores with independent systems annual layers surrounded on the periphery by one common system.
Dry-sidedness- a section of the trunk surface that has become dead during the growth of the tree as a result of damage.
Sprouting- a healing or overgrown wound.
Cancer- a depression or swelling on the surface of a growing tree as a result of the activity of fungi or bacteria.
False core- a dark, unevenly colored zone, the border of which does not coincide with the annual layers, separated from the sapwood by a dark border.
Wood spotting- coloring of sapwood of deciduous trees in the form of spots and stripes, close in color to the color of the core.
Internal sapwood- adjacent annual layers located in the core zone, their color and properties are close to the color and properties of sapwood.
Water layer are called areas of core or mature wood with a high water content.
The hardness of wood primarily depends on the type of wood, and also to a large extent on the growth conditions of the tree, humidity, etc. Within one type, the spread of values can be quite significant. Averages are usually indicated relative indicators Brinell hardness as a percentage relative to oak, the relative hardness of oak is taken as 100%.
Strength is the ability of wood to resist destruction under mechanical loads. It depends on the direction effective load, wood species, density, humidity, presence of defects and is characterized by tensile strength - the stress at which the sample is destroyed.
There are main types of forces: tension, compression, bending, shearing.
Thus, when choosing materials and wood products, you should take into account the above characteristics and not purchase products with defects and defects in wood. As a rule, low-quality wood is not used for the production of products, but only your vigilance will help you avoid purchasing low-quality products that do not meet norms and standards.
Sawing lumber- a fundamental process in wood processing. First, we need to recall a few terms that are used in the woodworking industry and which are defined by GOST 18288-87 sawmill terms and definitions:
Lumber. Materials that have one or more straight sides. Depending on the ratio of length to width and the number of parallel sides, timber, beams, boards, obapol and sleepers are distinguished.
- Bruschi- thickness less than 100 mm, width does not exceed double thickness. This category also includes slats, only linear dimensions there are significantly fewer of them.
- timber- thickness more than 100 mm, width does not exceed double thickness.
- Boards- the width exceeds two thicknesses, they can be trimmed (all four sides are trimmed) or unedged (the sides are not trimmed).
- Sleepers- this is a timber with strictly certain sizes, applied during construction railways, is rarely used nowadays.
- Lagging- the more common name is “croaker”, outer side the whip has only one flat surface. Most often used for further processing into wood chips.
Wood sawing methods
This is very important factor, the overall yield of lumber and its quality largely depend on the chosen method. Depending on the direction of cutting to the annual rings, there are two methods:
- Radial. The highest quality lumber has an excellent structure and high levels of physical strength. The saw moves perpendicular to the annual rings.
- Tangential. It produces a significantly higher yield of lumber, but its quality is somewhat lower. The saw moves parallel to the annual rings or in a tangential direction.
The choice of a specific cutting method depends on the end use of the lumber and the condition of the log. On the Internet you can find “strange articles” about circular sawing and so on. In fact, the vast majority of the logs are in one position during sawing; as a result, some of the lumber has a tangential cut (about 2/3 of the total), and the rest of the lumber has a radial cut. The top and bottom of the log are sawn tangentially, only its middle is sawn radially.
According to customer's request or taking into account own production the whip can be sawed from the sides, then turned 90°, and sawing is done again. As a result, some of the boards are unedged, tangentially cut, and the rest of the boards will be edged with a radial cut. Let us repeat once again that cutting methods are selected in each specific case separately, taking into account the above factors. Currently, there are three types of sawmills, each of them has its own advantages and disadvantages. Let's talk about them in more detail.
Frame sawmills
These were the first mechanisms that began to be used for mechanical sawing of wood. Today, in our opinion, they have undeservedly gone out of fashion. Let's take an objective look at their advantages and disadvantages.
To make it clearer, you need to learn about the principles of operation. On a frame sawmill, several saws are fixed in a vertical position (from ten or more, it all depends on the size of the frame), the distance between the saws is set once, sawing is carried out by the vertical movement of all saws with the simultaneous feeding of the blade.
pros.
- The entire process can be completely mechanized
- The sawmill is easy to set up and maintain
- Performance is at a very acceptable level
- Cuts the entire length of wood in one pass
- All received unedged boards can be trimmed simultaneously and also in one pass
- The edged board is obtained High Quality
- Save time
Minuses
- It is believed that these sawmills are converted into sawdust a large number of wood But this is only true for older models. Previously, saws were made from low-quality steel, the thickness of each saw was up to 3 mm, plus the spread of the teeth, the cut increased to 5 mm. Today, by reducing the thickness of the saw and the angle of the teeth, the thickness of the cut is significantly reduced. We will compare the thickness of the cut with the band sawmill below, you will find out what their manufacturers are silent about.
Band sawmills
They are considered the most advanced equipment, the most productive, the amount of sawdust is minimal. We will discuss this later, but first we will briefly describe their structure and principle of operation. The cutting is done with closed high-speed saws, the thickness of the saws is small, the width of the cut is reduced. The cutting occurs due to the forward/reverse movement of one saw along the blade. To be honest, we don’t notice any particular advantages (for the buyer), but there are disadvantages. In order not to be unfounded, we will talk about the intricacies of the cutting process.
Sawmills require a very careful attitude. Incorrect sharpening of the teeth, incorrect tension or selection of cutting speed (all of these parameters are selected taking into account the type of wood) lead to the fact that the lumber gets a wavy surface. The height of the waves can reach several centimeters. And such waviness of even one board negates all the “advantages of thin cutting.” A wave on lumber is a visible processing defect and reduces the grade of lumber. The classification of wood defects is described in detail in the article of the same name.
These sawmills have rather low productivity and require a lot physical labor. For example, if your log has a diameter of 100 cm, then calculate how many passes back and forth you need to make to cut it into boards 2 cm thick, and the frame sawmill will cut it in one pass. In addition, each sawn board must be manually removed from the sawmill and stored in separate place. In this case, after each cut you have to set the saw level again. Very high degree of danger during operation. The risk of injury while working at such a sawmill increases in geometric progression- this is both the saw breaking at high speeds and the presence metal objects in the body of the tree (and this happens not so rarely). Problems with sawdust removal. They scatter along the entire length of the sawmill, removing them is long and difficult.
Of course, manufacturers of band sawmills are “bashfully” silent about such “subtleties”. We advise you to take into account when choosing a sawmill maximum amount factors: the required volume of lumber, the availability of qualified personnel, the characteristics of lumber and requirements for their quality. After all, professional workers band sawmill produce 1st grade lumber in accordance with GOST.
pros.
- Relatively inexpensive
- Sawing in both horizontal and vertical directions
- Large whip thickness, up to 400 mm
- Low waste percentage
- Clean saw
Minuses
- Poor performance
- Increased danger
- Complex setup
- Highly qualified personnel
- Mandatory "rest time" from 8 to 10 hours
- Cleaning
Disc sawmills
Circular saws differ from band and frame (multi-saw) sawmills in the quality of edges and parallelism of the face. Lumber produced at disk sawmill is rightfully considered the best, but only from the consumer’s point of view. The main fact that makes lumber produced on a circular sawmill unavailable for consumption is its high price. High price does not allow you to compete in the market building materials, despite the excellent quality of boards and timber produced by this method. This circumstance is connected with three facts that influence the increase in the cost of lumber from a circular sawmill:
Summarize: when choosing edged lumber It is necessary to take into account not only the method of sawing lumber, but also the qualifications of the personnel servicing this equipment. You can buy good quality lumber from a trusted supplier by looking at the products using the photos offered on the manufacturer’s website or by visiting the finished product warehouse. The Elka-Palka company is ready to offer its services in accordance with the price lists listed on our website. We sell only high-quality products of our own production or purchased from trusted suppliers. Mandatory quality control.
Lumber - wood materials (beams, boards and whetstones) obtained by sawmilling. There are lumber of radial, tangential and mixed sawing. Lumber with sawn edges is called edged, while lumber with unsawed edges is called unedged.
Large, high-quality logs (these are logs from the bottom, butt part of the tree) provide the most valuable lumber. When sawing such logs, you need to decide on the thickness of the resulting boards in order to maximize the volume and cost of the resulting material. Since prices for lumber depend on its thickness, and in addition, when sawing at thick timber less sawdust is produced, this decision seriously affects income. However, if the quality of the thick material is lower, even if the best edge is almost pure, then sell it for good price It won't be easy. The sawyer should try to reduce the size of the material being cut when he sees that the quality of the wood begins to decline.
If the log is good, producing large lumber and railroad ties from the central part of the log is, to say the least, unwise. Because the price of timber is always less than the price of boards.
For high grade logs, circular sawing is recommended. In fact, cutting to the taper of the log and angling the log so that the cut is parallel to the bark is recommended for all "good" edges. The result will be clean wood along the entire length, more valuable pieces of lumber, and this will avoid the need to saw the clean wood later into short pieces. When you reach the low-grade part of the log, move on to the shape of the beam and minimize the operation of cutting the beam on the sides.
Durable but low-quality logs should be cut as quickly as possible. These logs are of little use - 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 is suitable here. Most often they are sawed onto timber, or simply sawed right through. Turning logs into in this case In general, it is better to reduce it to absolute zero.
Fragile logs provide such an insignificant profit and such a huge risk of breaking the product that it is better not to deal with them at all.
Average quality logs can produce significant amount good lumber, and here a lot depends on the sawyer, on how he will turn the log over. Here the decision to rotate the log is critical to profit.
First, you need to select the worst part of the log and cut it without taking into account the runoff. But you can't cut too much on this side. For small logs, you generally 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 over to the opposite side.
Another way is to choose the best side of the log and start cutting taking into account the taper of the log. Then this particular part is sawed for a long time before the log is turned over.
Lumber is sawed from one side until the sawyer expects that the next board on that side of the log will be at least as good as the boards that can be obtained from the other side. There is an exception: if you start sawing from the worst edge of the log, you must saw until you get a completely smooth cut surface in order to turn the log over onto it. In other words, the good side of the log needs to be cut deeply, and the bad side is simply removed with a layer or layer and one board.
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 that need to be additionally trimmed on the sides, and using less effective method, always turning to the adjacent face, we get 13 such boards. This circumstance alone can already be a significant argument in favor of turning the log 180°, especially for small enterprises. In addition, this sawing method gives more wide boards, and they are usually more valuable. When flipped over to the adjacent edge, you get 8 tangentially cut boards, which are subject to severe warping when drying. Further, if it is walnut or red oak with a narrow sapwood part, then with a 180-degree turn of the log we will get 10 boards with sapwood, with another turning method - 13 boards. Sapwood causes problems during drying. And when the log is turned 180 degrees, the internal tension of the wood is relieved, which results in the avoidance of cracks and cracks.
Turning over to an adjacent edge may be easier, but from an economic and cutting safety point of view, rotating the log 180° is more beneficial.
After 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, without taking into account the taper of the log. However, a good quality edge should always be sawn parallel to the bark to increase yield. good lumber from a 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 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 cutting on the sides, 15-1 cm is recommended, and not 15 cm.
If the edge is of poor quality, then it makes sense to cut boards with a width of at least 10-1 cm. The length of such boards should be at least 1.2 m. In general, you need to produce boards of no less length at your sawmill.
When it comes to logs of frankly poor quality, it makes sense to cut them from the “belly” or from the “ears”, rather than looking for a good edge. The "ears" are usually removed in 1 or 2 passes of the saw, revealing smooth surface inside the log. Cutting from the belly requires more manipulation, and as a result you get several short, but clean boards.
Timber has a number of advantages compared to thin boards. The timber often has a beautiful wood pattern that buyers love. When dried, it dries out half as much as boards (3% versus 6% for boards). Less cracking during drying. When humidity changes environment the timber is more stable. When the floor is covered with it, it hardly wears out.
Also, when sawing timber, the exit useful product from logs is 20% lower. Its production speed 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 the boards, greatly reduce the strength of the material.
Radial called 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, are practically not subject to deformation and have high wear resistance. The radial cut board has a shrinkage coefficient = 0.19% and a swelling coefficient = 0.2%. These indicators for radially cut lumber are twice as good as for tangentially cut boards. For a radial cut board, the process of shrinkage and swelling occurs along the width of the fibers - the thickness of the board, and for a tangential cut along the width of the board because the fibers of the “tangent” are located along the width. Accordingly, at the floor board, parquet board, imitation timber, block house, lining of radial cut, there are practically no cracks compared to similar products of tangential cut. Since the yield of radial cut boards is 10 - 15% of the total volume, their cost is quite high.
Radial cutting of wood is a method of cutting a log in which all the fibers in the board run along the direction of the annual rings. When radially cut, lumber has the best physical and mechanical properties. The strength and hardness of wood with radial cutting is higher than with tangential cutting.
The yield of radial cut boards is usually small (does not exceed 30%). On the UP-700 longitudinal sawing machines, the yield of radial cut boards reaches 60%. This high rate is achieved thanks to the cutting optimization system. By choosing among the optimization criteria the maximum output of a radial cut board, the conditions of radial and semi-radial cutting, the technologist determines the percentage of output of the radial board.
Radial cutting can also be done using other equipment. But the percentage yield of a radial cutting board on other equipment depends on how the operator cut the log. Typically this figure is significantly less than 50%. Due to the microprocessor control system and optimization system on the UP-700, you can obtain the maximum possible number of radial cut boards.
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| Cut texture: 1 - tangential cut; 2 - radial cut; 3 - semi-radial cut. | ||
Tangential 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 wave-like pattern of annual rings. Tangential cut boards have more high odds shrinkage and swelling, but are more affordable.
Sawing hardwood
The sawing operation involves decisions about board thickness, turning the log, and compensating for the log's taper. This depends on many factors: 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 schemes cut:
Simple sawing
The log is sawed until its core is exposed, and then turned 180° and sawed to the end. This is the fastest and easiest sawing method; however, with this method, each piece of lumber must be cut on the sides. Lumber sawn in this way is somewhat wider and heavier, of lower quality and has a lot of waste. It is extremely susceptible to warping during drying. Therefore, simple sawing or sawing through is justified only in the case of very low quality logs, when all of the above disadvantages are no longer particularly important.
Circular sawing
When sawing in a circle, a cut is first made, and the log is turned over to a new edge, sawed, and turned over again until at least 5 turns have occurred. From a financial point of view this is best way for logs of medium and high quality, although at the same time, at some sawmills it is difficult to carry out such a log turnover, and the daily productivity will be low. Of course, a machine with hydraulics solves this problem.
Sawing timber
Sawing timber maximizes productivity sawing machine(number of boards per day) and, as a rule, is used in industry when working with logs of medium and large sizes. In this case, the log is first sawn as in circular sawing, but the central part of the log, which can have dimensions of 18x23 or 25x25 and so on, is either transferred for processing to another machine along the production line, or sold as a large and heavy beam. Basically, logs of medium and low quality are sawn in this way, when it is impossible to obtain valuable lumber from the central part of the log. This saves time and effort in producing a product that is not of very high quality and therefore not of very high price.
Deciding which side of the log to start cutting on, which cut surface to open first, is the most important part of sawing. We divide the log into 4 sides, 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 timber, two basic rules apply:
The worst edge of the log is sawn first without any consideration for the taper of the log. Counting the slope of a log 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 produce 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 do the opposite, the best side The logs should be sawed parallel to the bark, without lifting or tilting the log. This means that from this best part of the log more boards of high quality will come out, which also match the length of the log.
Cut the best edge of the wood first, taking into account the taper of the log. This means that the log needs to be raised or tilted so that the first cut is made parallel to the bark.
The end result of both methods will be approximately the same, but the second method has one advantage. In this case, it is easier for the sawyer to rotate the log, because the open edge is the cleanest and has no defects. In the case of the first rule, the best part of the tree is the part opposite the open edge. It is not visible, and it is impossible to accurately rotate the log. Usually, if the wood is of good quality, then both rules work almost the same. But if you encounter a worse log, it is better to use the second rule.
Sawing soft wood
Many of the techniques used for sawing hardwood are also suitable for softwood. But there are also some differences. Of course, safety considerations must take precedence over the desire to produce as much product as possible.
Position the log so that when sawing, minor defects in the material appear inside the lumber, of course, if these defects are not so serious as to affect the strength of the final product. If possible, you should cut so that all knots and defects are located on one side of the lumber, while the other side remains clean. True, in the case of building materials, a clean surface does not affect the final price of the product. But large branches or defects can affect the strength of the structure.
Select 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 salable.
After the log has been sawn from the bad edge along the entire length of the log, you need to move to the opposite edge and cut parallel to the bark. From a good edge, the width of the board being cut 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 turn a log from one side to another if the lumber is made of new frontier will best quality than from the one that was just sawed.
Logs from waste. It is necessary to cut the “ears” in one pass of the saw, then turn the log over onto its “belly”, perhaps at least a few short boards can be made from it.