Lumber is obtained by cutting logs (blanks). In essence, these are sawn products of a certain size with two plane-parallel sides (layers). Sawing can be both radial and tangential.

In fig. 1 presented different kinds lumber - from plate to edged board.

Figure 1. Types of lumber: a - plate; b - dvuhkatny bar; в - not edged board; g - quarter; d - four-edged timber with wane; e - half-edged board with wane; g - clean-cut timber; h - croaker; and - edged board; k - planed grooved boards; 1- face; 2 - edge; 3 - rib; 4 - butt end; 5 - wane

The following elements are distinguished in lumber: layer, edges, ribs, ends. The seam is the longitudinal wide side of the lumber, as well as either side of the square lumber. The best face of the lumber has the least amount of defects, the best quality of processing. The layer of lumber facing the heartwood is called the inner layer, and the layer facing the sapwood is called the outer layer. The edge is the longitudinal narrow side of the lumber. Rib - the line of intersection of two adjacent sides of lumber. The butt is the end transverse side of the sawn timber. Shedding is not an obligatory element of sawn timber, it is, so to speak, an element of scrap of edged boards due to the non-conditionality of the source material (logs or billets).

Lumber is manufactured in accordance with GOST 8486-86E:

1) from coniferous wood - pine, spruce, larch, cedar and fir;

2) from hardwood - beech, birch, alder, linden, aspen and poplar.

Used: boards with a thickness of 100 mm or less with a width to thickness ratio of 2 or less; beams with a thickness of more than 100 mm (four-edged and two-edged).

The length of sawn timber: coniferous species no more than 6.5 m, deciduous - no more than 5 m. For special structures, sawn timber up to 9 m long, made on special order, can be used. The thickness and width of sawn timber are determined by the assortment (table 1, 2, 3).

Table 1. The norm of the output of edged sawn timber for 1 m 3 of logs

Note:

1) With an increase in the variety round wood before the 1st, the standard for the output of sawn timber increases by 3%.

2) With a decrease in the grade of round timber to the 3rd, the standard for the output of sawn timber is reduced by 2%, to the 4th grade - by 7%.

3) With a mixed supply of large and medium-sized logs, the standard for sawn timber output is taken as the arithmetic mean between medium and large logs.

Table 2. Thickness and width of sawn softwood in mm

Table 3. Thickness and width of sawn hardwood in mm

The ends of lumber and rough workpieces must be sawn at right angles to the longitudinal axis. Cane beams (with a partial absence of a cut in the edge) with a section of 120 x 120 mm or more must have a cut at the thin end of at least one third of the side of the beam.

The highest permissible moisture content of sawn timber for load-bearing structures- 25%, for glued structures - 15%.

The use of hardwood lumber is allowed for rafter parts, internal stairs, interior cladding walls and partitions, filing ceilings, rolls, gables, interior architectural details, joinery and clean floors.

The use of birch, linden and poplar wood for rafters is not allowed; linden, alder, aspen and poplar for treads wooden stairs; linden and poplar for clean floors.

To obtain a high percentage of lumber from round logs at the output, several different technologies, including certain cycles of actions. The time of sawing round timber and the labor input of the process are different, depending on the selected processing method, place of work, season. So, some enterprises build workshops for the primary processing of raw materials near the place of timber harvesting and save on this.

Not only trunks are processed, but also large branches. Roundwoods are sorted by size and bark. The trunks that have not passed the sorting are used in the future for rough work (manufacturing scaffolding and etc.). When accepting raw materials from the supplier, not only the cubic capacity is checked, but also the presence of damage, rot, knots - such materials do not correspond technical specifications... Defects in wood reduce the percentage of finished products at the output, and knots can damage equipment.

Before sawing, trunks are often debarked (bark removal on a special machine) - this process is optional, but considered economical:

• due to the absence of stuck pebbles and sand in the bark, the saw is protected from premature wear;
• the quality of the chip material increases;
• some enterprises do not accept slabs from unbarked logs for processing;
• the inaccuracy of the results when sorting timber with the help of electronics is reduced.

Types of forest cutting

First of all, you need to decide on the type of cut - there are several of them. Tangential - the cut goes tangentially to the annual rings, the surface is obtained with patterns in the form of rings, arches. Boards obtained in this way are cheaper, but have high percentages of shrinkage and swelling.

Radial - cut along the radius, perpendicular to the growth rings, the pattern is uniform, the output of the board is small, but it is of higher quality and greater strength.

Rustic - carried out at any angle, defects, knots, sapwood, etc. are visible.

Cutting methods

The cutting method is selected for each specific case.

Vrazval is the most economical, with almost no waste, a high percentage of finished timber. At the exit, unedged boards and two slabs are obtained.

With a bar - first, a two-edged bar, unedged boards, two slabs are obtained. Then the timber is sawn perpendicular to the saw cut into edged boards, at the edges two unedged boards and two slabs are obtained.

Sector - first, the log is cut into 4–8 sectors, and then each of them into radial or tangential materials. Sometimes in the center, a few not edged boards.

Breakup-segment - with such a cut, two or more unedged boards are cut out in the center of the trunk, and edged one-sided boards are sawn from the sides - from the segments.

Lumber-segment - similar to the breakup-segment, only in the middle of the log a two-edged timber is cut, which is then sawn into edged boards. The percentage of sawn timber output is large.

Circular - after sawing off one or several unedged boards, the log turns 90 0 and the following boards are sawn off. This method is used when a large log is affected by heart rot in the center. It separates healthy wood from low-quality wood.

Aggregate - using milling tools and circular saws, simultaneously with high-quality sawn timber, technological chips are obtained at the output (instead of slabs and slats). Such complex timber processing allows the rational use of raw materials and labor costs. The result is a waste-free production of finished lumber.

Required tool

The choice of tools depends on the amount of planned finished products, their quality and the size of the products. Most often, the sawing is performed circular saw... At certain stages of production, the use of special machines is required.

The circular saw makes precise cuts in all directions, handles all log sizes perfectly, is suitable for the professional and home use.

It is used for home use, when it is necessary to prepare not a large number of lumber. It's easier to do more difficult work with a chainsaw than buying expensive equipment. You will only need to special nozzle, trunk fixer and saw guides.

Bark stripping machines. They are quite expensive, but with regular use in an enterprise where large volumes of work are performed, they quickly pay off. It is not necessary to use them, but it is desirable because they can obtain a number of economic advantages and convenience in the production process.

And you will also need:

• Disc machine - for obtaining unedged materials from the forest at the exit.
• The band sawmill produces high-quality sawn timber and a low percentage of waste.
• Frame sawmill - does not need a foundation and can be installed directly in the field of logging.
• Universal machines are capable of producing high-quality material even from low-grade wood.

At enterprises with mass production, in order to obtain ultra-precise and high-quality products, whole complexes are installed modern equipment, and timber cutting is carried out of any complexity.

Cutting flow chart

To calculate the optimal percentage of obtaining finished sawn timber from a log, a forest sawing map is drawn up. You can do these calculations yourself or use a special computer program... Such information can still be obtained in the usual reference book, which contains information on the conduct of sawmilling operations.

The cutting plan allows you to determine how much will be at the output finished products what percentage of waste will be recycled. Based on these data, you can determine the final cost of production. The result can largely depend on the type of forest. There are some measures to increase the percentage of lumber yield.

The percentage of lumber on the way out is ready-to-use, useful wood. Waste is a raw material for obtaining MDF boards, Chipboard, fiberboard. These volumes will depend on the diameter of the tree, the types of solid wood products made, and the sawing option.

Percentage of round timber

Accurate calculation of each cubic meter of wood, an expensive natural raw material, is important at every woodworking enterprise. Cubic meters of round wood are calculated in several ways.

By the volume of transport. For each type of transport, its own timber volume is calculated and established. For example, the carriage holds 70.5 cubic meters of round timber. Then in three cars it will be 22.5 cubic meters. This method of counting speeds up the acceptance of raw materials, this is especially important when there is a large amount of incoming cargo. But at the same time, there is a large error in the results of calculations in this way.

Calculation based on the volume of one barrel. If the entire logging consists of timber of the same size, then having calculated the volume of one, you can count them all and multiply by the cubic capacity of one. This method is more accurate, but requires a lot of time and involvement. more workers for receiving cargo.

Automated systems with measuring frames. These measurements give higher percentages of accuracy than those taken by humans. When the logs pass through the measuring frame, all the thickening and curvature of the trunk and even knots are taken into account. In this case, you can immediately sort the trunks.

The method of calculation is by multiplying the volume by a factor. The height, width, length of the stack are measured and multiplied by a factor. This calculation is fast, but with a low percentage of accuracy. It is used when it is urgently necessary to determine the amount of cubic meters.

Dependence of the final percentage of output on the sawing technology

To increase the yield of finished lumber, it is necessary to optimize the sawing process itself. This is especially true when working with workpieces that have curvature, damage or other flaws:

• First, you need to select and start production only high-quality timber.
• Then select trunks with damage at the ends (rot, cracks) and rip off these places.
• With a section of the trunk with a rotten core, it is necessary to remove it, and cut the remaining wood into lumber. They will be shorter, but of better quality.
• And also for obtaining a high quality board, the circular sawing method is suitable.
• Higher yield when sawing large diameter timber.

The yield also depends on the quality of the log, the type of wood, the equipment used. New high-quality, well-tuned equipment makes it possible to handle trunks with almost no losses.

The efficiency of forest cutting can be increased if special measures are taken in advance. To do this, you need to make accurate calculations using digital programs. If you do it manually, then the percentage of rejects at the output will be higher. It should be taken into account in advance that a greater percentage of the output of sawn timber is obtained from coniferous forest species. Because their trunks are even, large, less prone to decay and therefore almost without marriage. A large volume of deciduous trees is often discarded.

For the rational use of wood, it is better to take short logs. But in domestic production, they usually take trunks with a length of 4 m or more for sawing. Due to their curvature, a large percentage of scrap is obtained at the output.

Sawing lumber- the fundamental process in wood processing. First, you need to recall a few terms that are used in the woodworking industry and which are defined by GOST 18288-87 sawmill production terms and definitions:

Lumber. Materials that have one or more flat sides. Depending on the ratio of length to width and the number of parallel sides, timber, bars, boards, obapol and sleepers are distinguished.

• Bars- thickness less than 100 mm, width does not exceed double thickness. Slats also belong to this category, only their linear dimensions are much smaller.
• Beams- thickness over 100 mm, width does not exceed double thickness.
• Planks- the width exceeds two thicknesses, can be trimmed (all four sides are cut off) or unedged (the sides are not cut off).
• Sleepers- this is a timber with strictly defined dimensions, used during construction railways, is rarely used now.
• Lagging- the more familiar name "croaker", outer side whip, has only one smooth surface. Most often it is used for further processing into chips.

Sawing methods of wood

This is very important factor, the overall output of lumber and their quality largely depends on the chosen method. Depending on the direction of the cut to the annual rings, there are two ways:

• Radial. The highest quality lumber, has an excellent structure and high rates in terms of physical strength. The saw moves perpendicular to the annual rings.
• Tangential. It gives a significantly higher output of sawn timber, but their quality is somewhat lower. The saw moves parallel to the annual rings or in a tangential direction.

The choice of a particular sawing method depends on the end use of the lumber and the condition of the whip. On the Internet, you can find "strange articles" about sawing in a circle and so on. In fact, the vast majority of logs are in one position during sawing, as a result, part of the sawn timber has a tangential cut (approximately 2/3 of the total amount), and the rest of the sawn timber has a radial cut. The top and bottom of the log are sawn tangentially, only the middle of the log is sawn radially.

At the request of the customer or taking into account own production the whip can be sawed from the sides, then tilted by 90 °, sawing is performed again. As a result, a part of the boards is not edged with a tangential cut, and the rest of the boards will be edged with a radial cut. Once again, we repeat that cutting methods are selected in each specific case separately, taking into account the above factors. There are currently three types of sawmills, each with its own advantages and disadvantages. Let's talk about them in more detail.

Frame sawmills

These are the first machines to be used for mechanical sawing of wood. Today, in our opinion, they are undeservedly “out of fashion”. Let's objectively consider their advantages and disadvantages.

To make it clearer, you need to learn about the principles of work. On a frame sawmill, several saws are fixed in a vertical position (from ten or more, it all depends on the size of the bed), the distance between the saws is set once, sawing is carried out by vertical movement of all saws with simultaneous feeding of the whip.

pros.

• The whole process can be fully mechanized
• The sawmill is easy to design and maintain
• Performance is quite acceptable
• Saws the entire whip in one pass
• All obtained unedged boards can be made edged at the same time and also in one pass.
• The edged board is of high quality
• Save time

Minuses

• These sawmills are believed to convert large amounts of wood into sawdust. But this is only true for outdated models. Previously, saws were made of not very high-quality steels, the thickness of each saw was up to 3 mm, plus the set of teeth, the cut increased to 5 mm. Today, by reducing the thickness of the saw and the angle of the set of teeth, the thickness of the cut is significantly reduced. We will compare the cutting thickness with the band sawmill below, you will find out what their manufacturers are silent about.

Band sawmills

Considered the most perfect 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. Cutting is performed with closed high-speed saws, the thickness of the saws is small, the cutting width is reduced. Cutting occurs due to the forward / reverse movement of one saw along the whip. To be honest, we do not notice any special advantages (for the buyer), but there are disadvantages. In order not to be unfounded, let's talk about the intricacies of the cutting process.

Sawmills require a very careful attitude towards themselves. Incorrect sharpening of the teeth, incorrect tension or the choice of cutting speed (all these parameters are selected taking into account the type of wood) lead to the fact that the lumber receives a wavy surface. The height of the waves can reach several centimeters. And such waviness of even one board negates all the "advantages of a thin cut". Wave on the lumber is a visible processing defect and reduces the grade of the lumber. The classification of wood defects is described in detail in the article of the same name.

These sawmills have a rather low productivity, they require a lot of manual labor. For example, if your whip has a diameter of 100 cm, then count how many roundtrip passes you need to make to cut it into 2 cm thick boards, 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 a separate place. In this case, after each cut, you have to set the level of the saw again. Very high operational hazard. The risks of injury while working on such a sawmill increase in geometric progression- this is the breakage of the saw at high speeds, and the presence metal objects in the body of a tree (and this happens not so rarely). Problems with cleaning sawdust. They scatter along the entire length of the sawmill, and it is long and difficult to remove them.

Of course, manufacturers of band sawmills “shyly” keep silent about such "subtleties". When choosing a sawmill, we advise you to take into account the maximum number of factors: the required volume of sawn timber, the availability of qualified personnel, the features of sawn timber and the requirements for their quality. After all, professional workers at the band sawmill produce sawn timber of the 1st grade in accordance with GOST.

pros.

• Relatively inexpensive
• Sawing both horizontally and vertically
• Large whip thickness, up to 400 mm
• Low percentage of waste
• Saw cleanliness

Minuses

• Poor performance
• Increased degree of danger
• Complex customization
• Highly qualified staff
• Compulsory "rest time" from 8 to 10 hours
• Cleaning

Disk sawmills

Circular saws differ from band and frame (multi-saw) sawmills in the quality of the edges and parallelism of the face. Lumber produced on circular sawmill rightfully considered the best, but only from the point of view of the consumer. The main fact that makes lumber produced on a circular sawmill not available for consumption is the high price. The high price does not allow you to compete in the market building materials, despite the excellent quality of the boards and beams produced by this method. This circumstance is connected with three facts affecting the increase in the cost of sawn timber from a circular sawmill:

Summarize: when choosing edged lumber, it is necessary to take into account not only the method of sawing the lumber, but also the qualifications of the personnel serving this equipment. Buy lumber good quality You can contact a trusted supplier, having familiarized yourself with the products according to the proposed photos on the manufacturer's website or by arriving at the finished product warehouse. The Elka-Palka company is ready to offer its services in accordance with the price lists indicated on our website. We sell only high-quality products of our own production or purchased from trusted suppliers. Mandatory quality control.

The ratio of the volume of produced sawn timber V n to the volume of cut raw materials Vc percentage is called volumetric output R, %:

This is the main indicator of the rationality of the use of raw materials, because in the cost of sawn products, raw material costs account for 80% of all production costs. The volumetric yield is proportional to the diameter (for example, when sawing logs with a diameter of 16 cm and a length of 6.5 m, when sawing into collapse, it is about 55%, with a diameter of 32 cm - 61.5%, with a diameter of 40 cm - over 63%) and inversely proportional to its length (for example, for every 0.5 m decrease in the length of logs from 6.5 m, it increases on average by 0.65%). A log curvature of 1% reduces the yield by 8 ... 12%. When sawing with timber, the output is 2.5 % higher than the collapse. An increase in saw thickness by 0.2 mm in a 7-saw set leads to an increase in wood loss and to a decrease in product yield by 0.3 ... 0.5%. The volumetric output of sawn timber is influenced by the organization of work, the qualifications of workers and engineers, technical supervision of equipment, and technological discipline at all production sites.

The output of sawn timber by grade as a percentage of the volume of sawn raw materials is called by-class output:

The total yield of all varieties gives volumetric output sawn timber

Distribution of the yield by varieties and assortments in % total volume of sawn timber С, = 100 V ni - V n% - there is a variety composition of products. The qualitative composition of sawn timber is assessed grade factor Ks, depending on the type of wood, purpose and grade. As basic assortment (K c= 1) accepted edged coniferous sawn timber with a length of 2 ... 6.5 m 3 grades (GOST 8486-86 *), (for selected grade K c = 2). The percentage ratio of the volume of specification sawn timber to their total volume is called specification output:

In order to stimulate sawmills for the integrated rational use of raw materials, a "so-called coefficient of integrated utilization of raw materials- the ratio of the total volume of sawn timber ( V p), other sawn products (obapola, container boards - V DP), technological chips (V Щ), technological sawdust (Von), sold to the side of waste (V P) and waste used for the production of steam and energy ( Vn / e) to the volume of sawn raw materials:

In this regard, equipment for the aggregate processing of raw materials appeared. Indicators of the degree and rationality of the use of sawn timber R, Rs, Rep, Kisp, are divided into planned and reporting.

Postav

The scheme for cutting a log or a group of logs for sawn timber of the required dimensions, which establishes the order and place of cuts, the thickness, and sometimes the width of the resulting materials, is called delivery, (in contrast to the so-called "set of saws" - a set of saws installed in multi-saw machines at a certain distance from one another to obtain boards and beams of certain sizes from logs). Postavy are symmetrical and asymmetrical... (rarely used, for example, when cutting out sleepers), even and odd... In even symmetrical positions, the core falls into the center cut and ends up in the two center boards, in odd positions - into the core board. Breakup and lumber couplings given parameters are called settlement: the set that provides the highest volumetric output of sawn timber is called maximum, and the set, providing the highest output of lumber of a given specification - optimal... Recording of deliveries is carried out according to nominal dimensions lumber (without allowances for shrinkage, taken into account when calculating the delivery). An even symmetrical breakup set is recorded in different ways, for example,

19-25-50-50-25-19 or 50 / 2-25 / 2-19 / 2 or:

2 boards 50 mm

2 boards 25 mm

2 boards 19 mm.

The bar set is recorded in two passes, for example:

a) 1st pass - 16-16-175-16-16, 2nd pass - 16-16-50-50-50-16-16;

b) 1st pass - 175/2 - 16/2 - 16/2, 2nd pass - 50/1 - 50/2 - 16/2 - 16/2;

c) 1st pass - 1 bar 175 mm, 2nd pass - 1 board 50 mm

2 boards 16 mm 2 boards 50 mm

2 boards 16 mm, 2 boards 16 mm

2 boards 16 mm.

Other types of delivery recording are also possible.

The thickness of the inter-saw strip is equal to the sum of the values ​​of the nominal thickness of the board, allowance for shrinkage in its thickness and double-sided widening of the saw teeth by flattening or spreading.

When drawing up and calculating the delivery, it is necessary to know the consumption of the delivery width A, mm - the distance between the symmetrical outer faces of the outermost side boards in the set, which is the sum of the nominal thickness of the boards, allowances for shrinkage and the width of the cuts e(at NS boards in place):

Drawing up supplies for a given specification of lumber with a known diameter of the logs consists in determining the number of boards and in the sequential selection (fitting) of their thicknesses into a given diameter of the logs. First, the most favorable diameter of the logs is selected to obtain a beam of a certain size, and then the thicknesses of the boards are selected for the first and second passes. Rules for the preparation of deliveries the following:

a) for mass cutting of raw materials, the supplies must be symmetrical;

b) the preparation of the setups should start from the axis of the log;

c) the number of sections cut from the log should be minimal - no more than 1-2 thicknesses of thick sawn timber and two thicknesses of thin timber should be obtained from the log;

d) should not be included in the delivery of boards of adjacent thicknesses with a difference of less than 5 mm, because they are difficult to sort;

e) do not cut out the central boards from logs 36 ... 62 cm and more thick, and core boards not thinner than 40 ... 100 mm, and from logs with a diameter of 14 ... 34 cm central 16 ... 44 mm, and core 32 .. .50 mm;

f) avoid multi-saw "heavy" setups: for log diameters from 14 ... 16 to 30. ..32 the number of boards in a set should be taken from 4 ... 7 to 8 ... 12;

g) take the height of the timber within 0.6 ... 0.8 of the top diameter of the log (Fig. 3.17);

h) get side boards on the 1st in 2nd pass of the same thickness;

i) the width of the set must be equal to or close to the limiting coverage of the diameter of the log set, depending on the minimum width b min board length l min(taken 1.5 m), on the diameter and length of the log D and L:

j) when sawing logs into collapse, the maximum and optimal thicknesses of the boards are set according to the graphs (Fig. 3.18) or according to the formulas;

l) the thickness of the outer boards in order to avoid gaps is recommended to be taken depending on the diameters of the logs: 16 and 19 mm with a diameter of 14-18 cm; 19 and 22 mm at 20-24 cm; 19, 22 and 25 with a diameter of 26-36 cm; 22 and 25 with a diameter of 38-42 cm; 25 and 32 with a diameter of 34-56 cm; 32 mm at
diameter 58 cm and more.

Calculation of deliveries- this is the determination of the width, length of the boards to be cut, their volume, volumetric and graded output for each section of the boards and in general for the log. The length and width of the boards are found graphically or analytically. On a sheet of paper, the circumferences of the top and butt ends of the log are applied to a certain scale and, starting from the center, the required sections of lumber are entered, the width is measured and the length of the boards is determined taking into account the run of the log. Sometimes templates made of transparent plastic are used. A widespread method for calculating the setups using the quadrant graph (Fig. 3.19).

To determine the length and width of unedged and edged boards and the dimensions of the timber on the abscissa axis, the distance from the axis of the set-up to the considered face of the board is found. From the obtained point, a vertical line is drawn up to the intersection with the calculated diameter and the intersection point is taken down to the ordinate axis, where the calculated width of the board is found. The allowance for shrinkage in width is subtracted from it and the result is rounded to standard width boards. The diameter of the top section can be used as the calculated diameter of the log. d or the diameter of any section d x, spaced from the top end at a distance x. The diameter of a log in any section is determined by the formulas:

where b x - cross-sectional board width, cm; α - distance from the axis of the log to the board layer, cm;

S- run of a log, cm / m.

The length of the shortened board is determined by the formula

Drawing up and calculating supplies is a very important and crucial stage in planning the cutting of raw materials. It determines the rationality of using wood when cutting. After drawing up and calculating each set, it is necessary to immediately determine the amount of raw materials to be cut, as well as the output of sawn timber from it and enter them into the list of the cutting plan (form 3.1).

Sort output of lumber C t,% of raw materials of various grades is determined according to the standards for the output of lumber of the determined grade R, R 2 Rz R 4,%, from logs of I, II, III, IV grades in volume (or in quantity), respectively Q 1, Q 2, Q 3, Q 4 m 3 (or pcs) and calculated by the formula

Determination of the volumetric output of lumber for each assortment and in general for delivery is carried out in cubic meters and percent of the volume of the log.

The cutting plan is drawn up for the entire volume of raw materials intended for processing within a month or for 1,000 m 3 (while maintaining the specific ratios of the sizes and quality of logs specified in the specification for a month) (form 3.3). On its basis, a schedule for sawing raw materials is drawn up, taking into account the possibility of its sorting and the timing of delivery of sawn products to consumers.

All operations for planning the cutting of raw materials can be performed on a computer.

Wood balance when cutting raw materials, this is the distribution of the entire volume of wood by types of products, waste and losses, reflecting the rationality of using wood and depending on the sawing methods, the size and quality of raw materials, the purpose of sawn timber, the used supplies, the thickness of the saws and other factors. Timber balance is planned (calculated) and reported (actual). For example, the balance of softwood sawn timber in the production of edged sawn timber in accordance with GOST 24454-80 * and 8486-86 contains: sawn timber 60%, process chips 18%, sawdust 14 %, waste (chip screening) 2%; shrinkage 6 %. (This does not include off-balance waste - bark 10 ... 12% and allowances for the length of logs 1%).

Table 3.3

Form 3.1. Cutting plan of raw materials for sawn timber

for a month 20 g.

Before sawing round timber, it is required to calculate how much volume will remain for further operation, and how much material will go for processing. This is important because it affects the final cost of the product. The amount of uncut obtained will depend entirely on what types of wood are used. At the same time, there are certain measures to increase the coefficient of output of sawn timber after cutting.

What is the percentage of yield and its dependence on the diameter of the sawn timber

To deal with this, it is necessary to reveal the concept itself. Roundwood lumber yield is everything useful tree after cutting. The rest is waste, which is sent for further processing to obtain materials such as MDF, fiberboard, chipboard. It should be understood that the volume that will be obtained as a result of cutting a tree is calculated for each individual diameter and the selected sawing option.

It is worth understanding the question of why the parameter under consideration depends on the diameter of the forest. Here everything is extremely simple: the fewer cuts on the tree, the higher the volume value. Of course, a lot will also depend on the cutting technology and on the sequence in which the cutting was carried out. The correct sequence will be shown in Fig. 2. It should be understood that small lumber is obtained from medium-sized wood species, and thick boards and beams are made from large woods. It is also worth considering the average diameters with the approximate rates of the volumetric flow rate:

• 14 - from 45 to 50%;
• 20 - about 52%;
• 25 - up to 57% on average;
• 34 - this diameter has squared timber, which has the highest volume fraction, equal to 66%;
• if the forest has a diameter of more than 40 cm, then there is a sharp decrease in the received materials.

Waste volume after sawing

In order for the finished product to have a large percentage, everything should be calculated and prepared correctly. And the work process itself must be carried out in full accordance with the technology. It should be borne in mind that the round wood of conifers and deciduous trees will give a different yield of lumber from unedged boards in m 3.

Note! Conifers are considered the best option, due to the fact that they have a straight barrel and relatively larger diameter... In addition, such a forest is not so susceptible to the process of decay, which leads to less waste.

When working with hardwoods, 2 processing methods are used:

1. Using band sawmill at 375 or 363.
2. Into the collapse. This technology provides for cutting a half-beam, which is subsequently passed through a multi-saw device.

In this case, the first method allows you to get about 40-50% at the output. But the collapse technique differs in a slightly larger volume - up to 70%. The disadvantage of this technology is that its costs are relatively high. When sawing round sawn timber with a length of 3 m, you can see enough high level marriage. In this case, the remaining wood will not be immediately useful due to the fact that it requires an additional processing process.