Before sawing round timber, it is necessary to calculate how much volume will be left for further use, and how much material will be spent on processing. This is important because it affects the final cost of the product. The amount of untrimmed wood you get will depend entirely on what type of wood is used. At the same time, there are certain measures to increase the yield of lumber after cutting.
What is the yield percentage and its dependence on the diameter of lumber
To understand this, it is necessary to unpack the concept itself. Percentage of lumber yield from round timber- this is all useful tree after cutting. The rest is waste that is sent for further processing to produce materials such as MDF, fiberboard, chipboard. It is worth understanding that the volume that will be obtained as a result of cutting wood is calculated for each individual diameter and selected cutting option.
It is worth understanding the question of why the parameter under consideration depends on the diameter of the forest. Everything here is extremely simple: the fewer cuts there are on the tree, the higher the volume value will be. 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 small species of wood, and thick boards and beams are made from large timber. It is also worth considering the average diameters with approximate rates of volumetric flow rate:
- 14 – from 45 to 50%;
- 20 – about 52%;
- 25 – on average up to 57%;
- 34 – this is the diameter of lumber, which has the highest volume fraction of 66%;
- if the forest has a diameter of more than 40 cm, then there is a sharp decrease in the materials obtained.
Volume of waste 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 technology. It should be taken into account that the round forest of coniferous and deciduous trees will give a different yield of lumber from non- edged boards in m3.
Note! Coniferous wood species are considered the best option, due to the fact that they have a straight trunk and are relatively larger diameter. In addition, such wood is not as susceptible to decay, which leads to less waste.
When working with hardwood, 2 processing methods are used:
- Using a 375 or 363 band sawmill.
- In ruins. This technology involves cutting out a half-beam, which is subsequently passed through a multi-saw device.
In this case, the first method allows you to get approximately 40-50% of 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 timber 3 m long, you can notice quite a high level marriage. However, the remaining wood will not be immediately useful due to the fact that it requires an additional processing process.
Repair and construction work often involves the use of lumber. But shops and timber trading centers often sell them not in pieces, but in cubes.
The number of edged boards in 1 cubic meter.
Everything is very simple and fast.
Method for calculating edged lumber
- a caliper, tape measure or folding m; if the length parameters of wood products are known, you can limit yourself to a regular ruler;
- calculator - suitable mobile phone, smartphone, if problems may arise with mental arithmetic;
- a piece of paper and a pencil - to record the results of calculations, how many boards are in a cube.
- Volume = Length × Height (product thickness) × Width.
To prevent confusion when converting cubic centimeters to cubic meters, it is more convenient to immediately record the measurement results in meters.
Calculation of the weight of a cubic meter of wood.
For example, 0.132 cu. m = 6 m × 0.022 m (2.2 cm) × 0.10 m (10 cm).
Now, to determine the number of planks in a cube, you need 1 cubic meter. m divided by 0.132. The result obtained (7, 5757) when purchasing timber must be rounded to 8 pieces.
This method of calculating cubic capacity is also suitable for timber. This way you can determine how many cubes of timber you need to purchase if you know the required number of products, or, conversely, determine the required number of cubes.
To determine the required volume of timber, the easiest way is to carry out calculations similar to the above method. Only the final result needs to be multiplied by 1.2 - a correction factor. From unedged boards you can get no more than 70-80% of edged ones.
The width and thickness of each product are measured taking into account its further processing. The technique will help determine the number of cubes wooden products, necessary for work, if the final result is planned for their further processing - pruning.
When purchasing, the widest and thinnest boards are measured to obtain an average width. If the width of the lumber at the butt is wider than at the top, the arithmetic mean of their dimensions is used without taking into account the bast layer or bark, rounded to 10 mm. In this case, fractions from 5 mm are rounded to the full 10 mm, and fractions up to 5 mm are not taken into account. The length and thickness of the lumber are measured in the usual way. The volume of timber is determined according to the usual scheme:
Scheme for calculating the cubic capacity of a log.
- the volume of one product is calculated;
- the total cubic capacity of purchased timber is determined; according to GOST, correction factors are used: 0.96 – for lumber from coniferous species, 0.95 – for lumber from deciduous wood.
In addition to the piecemeal method of determining volume, there is no edged lumber, the geometric method can be used.
Requirements for a package of unedged timber:
- lumber is laid tightly, without overlaps, in horizontal rows;
- on one side the ends of the boards are aligned;
- all sides of the package are strictly vertical: according to GOST, the displacement of individual products outward and inward should not exceed 0.10 m;
- The package of lumber must be the same width along its entire length.
Then the volume of the package is calculated, the resulting result is multiplied by the coefficient:
- 0.67 – the number of ends in the unaligned side of the package is more than 50% of the total number of boards;
- 0.50 – if there are only 50% ends;
- 0.33 – the number of ends is less than 50% of the total amount of timber.
Piece or geometric methods for determining cubic capacity will help you navigate when purchasing unedged timber. If you have problems with payments, you can seek help from a sales consultant, manager, or warehouse employee.
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Sawn timber yield rates from roundwood
In the report of the UN European Commission/FAO Timber Committee ECE/TIM/DP/49 on timber conversion factors different types forest products, in particular, the yield coefficients of sawn timber from round timber are given. These data, based on the experience of 16 countries, may well serve as guidelines for woodworking enterprises as world standards.Lumber covers a significant portion of solid wood lumber products. They include a wide range of products from unedged, fresh sawn to edged, dry, sized and planed lumber. The type of products produced has a significant impact on the yield of final sawn products from round timber. So from one cubic meter round wood you can get 0.8 m3 of unedged lumber and only 0.4 m3 of dry edged, sorted and planed lumber. That's why various countries was asked to provide their yield ratios for various categories of lumber products to understand why national lumber yield ratios differ so widely from each other.
For example, in Germany, 1.67 m3 of roundwood is required to produce 1 m3 of softwood lumber, while in the USA it is 2.04 m3. At first glance, it may seem that sawmilling in the United States is less efficient compared to Germany (the given coefficient indicates that the production of the same volume of lumber in the United States requires 22% more roundwood). But when taking a closer look at the production of the same types of lumber, such as rough lumber and dry lumber, it turns out that lumber yield rates in these countries are similar. This means that the differences in lumber yield ratios lie in the output various types finished products. Obviously, Germany produces more rough-cut lumber, while the USA produces more dry and planed lumber.
Some countries note that lumber production in their countries is recorded in the fresh sawn form to avoid double measurement of volumes for dry and planed lumber. This is in contrast to other countries, especially the Scandinavian region and North America, where the volume of lumber is most often given taking into account its final processing. This, for example, could result in a rough green lumber yield ratio of 1.57 (64%) or 1.75 (57%) for dry lumber or 2.27 (44%) for planed and finished lumber, as shown in the diagram below.
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Edged board is one of the most common lumber in construction. It is used for outdoor work, during construction wooden houses, interior decoration, manufacturing wooden fences. The board is sawn from logs and additionally sawed along the edges. This gives the lumber not only a marketable appearance, but also protects it from various pests. As a rule, the width of an edged board is twice its thickness.
The greatest demand in construction is for boards made from coniferous wood - spruce and pine, Siberian larch. For the production of furniture, more expensive and durable types of wood are used - oak, alder, ash.
The quality and cost of lumber depends on many characteristics: the type of wood, its moisture content, processing and sawing technology. Therefore, it is important to correctly calculate the yield of edged lumber in production.
depends on many factors: the specification, the grade of the board, the diameter of the saw log.
For example, from a coniferous round forest the yield of edged lumber is band sawmills usually 55 - 60%. On disk sawmills this percentage increases to 70-75%.
The yield of edged boards from round deciduous wood (aspen, birch, linden) is always very low for all types of sawmills. Approximately 35-40%. This is due to the curvature of hardwood logs. It is possible to increase the percentage output only by installing additional equipment - multi-rip, edge trimming and slab machines. The yield, in this case, will increase by about 20%.
Generally? prices for lumber fluctuate greatly, and many lumber companies provide edged boards at a price significantly lower than the market price. However, before you buy lumber from such sellers, you need to think about what pitfalls may be hidden here. Often the cost of boards is reduced due to the low quality of lumber. Thus, it is most appropriate to purchase edged boards from those companies for which selling wood is not a new thing.
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OKSTU 5330; 5309
Introduction period from 01/01/88
Failure to comply with the standard is punishable by law
This standard applies to unedged boards of coniferous and hardwood and establishes methods for measuring volume.
1. GENERAL PROVISIONS
1.1. The volume of unedged boards is recorded in dense cubic meters with an accuracy of 0.001 m³ based on the board dimensions (thickness, width and length) established for wood with a moisture content of 20% (relative to the mass of absolutely dry wood). The volume of individual boards is determined according to GOST 5306-83.
1.2. Three methods are established for accounting for the volume of unedged boards: batch, piece and sampling method.
1.2.1. The batch method of accounting consists in determining the volume of a package of boards and is used as the main one for accounting for the volume of any batches of unedged boards of softwood and hardwood, placed in packages, except for special assortments (aviation, resonance, deck, boat, barge construction) and boards of valuable species (oak , beech, ash, elm, maple and hornbeam).
The formation of the package should be carried out in accordance with the requirements of GOST 19041-85E, and in addition, the following rules must be observed:
a) on one side, the ends of the boards in the package must be aligned;
b) boards in horizontal rows of the package must be laid close to each other, but without overlapping one board over another;
c) the package must have the same width along its entire length, the sides of the package must be vertical. It is allowed to shift individual outer boards from the vertical side, both inward and outward, up to half the width of the board, but not more than 100 mm;
1.2.2. The piecemeal method of accounting consists in determining the volume of each board, summing these volumes and is used to account for the volume of any batches of unedged boards of special assortments, boards of valuable species and in case of disagreement, as well as to account for batches of unedged boards of all types and sizes with a volume of no more than 10 m².
1.2.3. The sampling method consists in determining the volume of production of boards or packages with the distribution of average results over the entire batch and is used to take into account the volume of any number of unedged boards of all species and sizes (except for special assortments and boards of valuable species), not packed into packages and in the case when the formation packages do not meet the requirements set out in clause 1.2.1.
1.3. The guarantee is considered to be the number of unedged boards or packages drawn up in one accompanying document.
1.4. In invoices-specifications for shipped unedged boards, the consignor is obliged to indicate which of the specified methods of volume accounting was used by him to determine the volume of a given batch.
The consignee must take into account the volume of unedged boards upon acceptance using one of the methods in which this batch was taken into account during shipment.
2. BATCH METHOD OF VOLUME ACCOUNTING
2.1. The batch method of accounting for the volume of unedged boards provides:
determination of dimensions (height, width and length of the package);
determining the folding volume of boards in a package;
determining the volume of the package in dense cubic meters;
2.1.1. Determining package sizes.
The height of the package should be determined from the side of the aligned end in the middle of its width by measuring without taking into account the spacers (Fig. 1) and found using the formula:
h = h 1 -nb
h- package height, m
h 1 - measured package height, m
n- number of spacers along the height of the package, pcs.
b- gasket thickness, actual
The width of the package should be determined by measuring from the side of the aligned end in the middle of its height between two conventionally drawn vertical lines limiting the sides of the package (Fig. 1).
Measurement of the width and height of the package must be carried out with an accuracy of 10 mm.
The length of the package (Fig. 2) should be determined as the sum of the lengths of the dense and loose parts of the package according to the formula:
l = l 1 - kl 2
l- package length is taken into account, m
l 1 - length of the dense part of the package, m
l 2 - length of the loose part of the package, m
To- coefficient taking into account the proportion of protruding ends in the loose part of the package.
The length of the dense and loose parts of the package must be determined by measuring with an accuracy corresponding to the gradation of lumber along the length according to GOST 24454-80 and GOST 2695-83.
The value of the coefficient “k” should be taken equal to:
2/3 - if the number of protruding ends is more than 50% of the number of boards of the entire package;
1/2 - if the number of protruding ends is equal to half the number of boards of the entire package;
1/3 - if the number of protruding ends is less than 50% of the number of boards of the entire package.
2.1.2. Determination of the folded volume of the package.
The folding volume of the package must be calculated by multiplying the height, width and length of the package, determined in accordance with clause 2.1.1.
2.1.3. Determination of the volume of the package in dense cubic meters (accounting volume).
The volume of boards in the package must be determined by multiplying the folded volume of the boards in the package by the stacking density coefficient given in table. 1.
Table 1
DENSITY COEFFICIENTS FOR CONVERTING FOLDED VOLUME
UNEDGED BOARDS IN THE VOLUME OF SOLID WOOD
a) for coniferous species
| Board length, m |
Board thickness, mm | |||||||||
| 16 | 19 | 22 | 25 | 32 | 40 | 44 | 50 | 60 | 75-100 | |
| Coefficient f 1 | ||||||||||
| 2,00 - 6,50 | 0,59 | 0,60 | 0,60 | 0,61 | 0,63 | 0,65 | 0,66 | 0,67 | 0,70 | 0,75 |
| 1,00 - 1,75 | for all thicknesses 0.67 | |||||||||
| Coefficient f 1 | ||||||||||
| 2,00 - 6,50 | 0,64 | 0,65 | 0,65 | 0,66 | 0,68 | 0,71 | 0,72 | 0,73 | 0,75 | 0,79 |
| 1,00 - 1,75 | for all thicknesses 0.73 | |||||||||
b) for hardwood
| Board length, m |
Board thickness, mm | ||||||||
| 19 | 22 | 25 | 32 | 40 | 45 | 50 | 60 | 70-100 | |
| Coefficient f 1 , for boards with a moisture content of more than 20% (relative to the mass of absolutely dry wood) | |||||||||
| 2,00 - 6,50 | 0,52 | 0,53 | 0,54 | 0,57 | 0,60 | 0,62 | 0,64 | 0,68 | 0,74 |
| 1,00 - 1,75 | for all thicknesses 0.66 | ||||||||
| Coefficient f 1 for boards with a moisture content of 20% or less (relative to the mass of absolutely dry wood) | |||||||||
| 1,00 - 6,50 | 0,58 | 0,59 | 0,60 | 0,63 | 0,67 | 0,69 | 0,71 | 0,75 | 0,82 |
| 1,00 - 1,75 | for all thicknesses 0.73 | ||||||||
2.1.4. Determining the volume of a batch of boards.
The volume of a batch of unedged boards packed in packages should be determined by summing the accounting volumes of individual packages in the batch.
2.2. In the event of a disagreement between the supplier and the consumer when accounting for the volume of unedged boards in batches, the accounting volume must be determined by control piece measurement, established by agreement of the parties, but not less than 6% of the delivered lot.
Packages should be selected evenly from different places parties. The deviation of the accounting volume using the batch method from the results of the control check using the piecemeal method should not exceed 5%. If the difference is greater, the volume of the tested batch of boards must be taken equal to the volume of boards obtained during the control test.
Note.
The volume of unedged boards used as spacers in packages should be determined by the actual number of spacers measured by piece.
3. PIECES METHOD OF ACCOUNTING VOLUME
3.1. The piecemeal method of accounting for the volume of unedged boards provides for:
determining the size of boards;
determining the volume of each board;
determining the volume of a batch of boards.
3.1.1. Determining the dimensions of the boards.
The thickness of the boards should be measured in accordance with GOST 6564-84 and accepted as nominal according to the dimensions established by GOST 24454-80 and GOST 2695-83.
The width of unedged boards should be measured in accordance with GOST 6564-84. If there is a local narrowing on the face in the middle of the length of the board, the width must be measured at a distance of 150 mm from it.
The length of unedged boards should be measured in accordance with GOST 6564-84 and taking into account the gradations established by GOST 24454-80 and GOST 2695-83.
The moisture content of lumber must be determined in accordance with GOST 16588-79.
3.1.2. Determining the volume of boards.
Volume unedged boards with a moisture content of more than 20% (relative to the mass of absolutely dry wood) should be found as the product of the volume calculated from the dimensions of the thickness, width and length of the board, determined in accordance with paragraph 3.1.1. using a correction factor for the width of the board equal to: for coniferous species - 0.96, for deciduous species - 0.95.
When determining the volume of unedged boards with a moisture content of 20% and below (relative to the mass of absolutely dry wood), correction factors should not be applied.
3.1.3. Determining the volume of a batch of boards.
The volume of a batch of unedged boards should be determined by summing the volumes of individual boards.
4. SAMPLING METHODS FOR VOLUME ACCOUNTING
4.1. The method for accounting for the volume of unedged boards provides:
selection of samples from the batch;
determining the volume of sample boards or sample packages;
determining the average volume of a board or package;
determining the volume of a batch of boards.
4.1.1. Sample size.
Samples must be taken from different locations in the lot being taken into account.
Samples of boards should be selected by selecting any board from the lot (fifth, tenth, hundredth or any other).
Samples of packages should be taken from a batch of packages of uniform dimensions containing boards of the same thickness.
The sample size must be set in accordance with table. 2.
table 2
|
Purpose of sampling |
Sample sizes |
||
|
Composition of the batch according to the length of the boards |
|||
|
Boards of the same length |
Boards of the same length mixed with up to 15% shorter ones |
Boards of no more than 4 adjacent lengths |
|
|
To determine the average volume |
Not less than 3% of the lot delivered, but not less than 60 boards |
Not less than 4% of the lot delivered, but not less than 80 boards |
Not less than 7% of the lot delivered, but not less than 120 boards |
|
To determine the average package volume |
At least 3 packages |
At least 4 packages |
At least 8 packages |
4.1.2. Determining the volume of sample boards and sample packages. The volume of sample boards should be determined by piecemeasurement in accordance with Section 3, sample packages - in batches in accordance with Section 2, while the boards in packages must be laid in accordance with the requirement of clause 1.2.1.
4.1.3. Determination of the average volume of sample boards or packages. The average volume of sample boards or packages must be determined as the arithmetic mean of the volumes of individual boards or packages.
4.1.4. Determining the volume of a batch of boards. The volume of a batch of unedged boards should be determined as the product of the average volume of a board or package by the corresponding number of boards or packages of the lot.
4.2. In case of disagreements between suppliers and consumers in the accounting of unedged boards using the sampling method, a repeated sample should be taken in double size. The resampling results should be taken to account for the entire batch of boards.
Examples of determining the volume of unedged boards are given in the appendix.
APPLICATION
Examples of determining the volume of unedged boards
for piece and batch measurement methods
Example 1. Find the volume of a raw unedged softwood board having a thickness of 25 mm (nominal), a width of 220 mm and a length of 5.25 m.
Using these board dimensions from the lumber volume table (GOST 5306-83), we find the board volume to be 0.0289 m³.
0.0289 x 0.96 = 0.0277 m³,
where 0.96 is the correction factor for the width for softwood boards.
Example 2. Find the volume of a raw unedged hardwood board having a thickness of 40 mm (nominal), a width of 180 mm and a length of 6 m.
Using these board dimensions from the lumber volume table (GOST 5306-83), we find the board volume to be 0.0432 m³.
The volume of the same board at a humidity of 20% (relative to the mass of absolutely dry wood) will be equal to:
0.0432 x 0.95 = 0.0410 m³,
where 0.95 is the correction factor for the width for hardwood boards.
To calculate the volume large quantity boards (using the specified method according to the tables of GOST 5306-83), you can not recalculate the volumes of individual boards into volumes in a dry state, but multiply the total volume of all wet boards by a correction factor for the width.
Example 3. Find the volume of raw unedged softwood boards 25 mm thick, folded into a package having a height of 980 mm, a width of 1030 mm and a length of 4.15 m.
0.98 x 1.03 x 4.14 = 4.189 m³.
From Table 1 we find the laying density coefficient for raw coniferous boards with a thickness of 25 mm - 0.61.
4.189 x 0.61 = 2.555 m³.
Example 4. Find the volume of dry unedged softwood boards with a moisture content of 20% (relative to the mass of absolutely dry wood), 50 mm thick, folded into a package having a height of 1250 mm, a width of 1150 mm and a length of 5.75 m.
The folding volume of a package of dry boards is equal to:
1.25 x 1.15 x 5.75 = 8.266 m³
From Table 1 we find the laying density coefficient for dry coniferous boards 50 mm thick - 0.73.
Then the volume of unedged boards in the package in dense cubic meters at a humidity of 20% (relative to the mass of absolutely dry wood) will be equal to:
8.266 x 0.73 = 6.034 m³
Example 5. Find the volume of raw unedged hardwood 32 mm thick, folded into a package having a height of 1100 mm, a width of 1000 mm and a length of 5 m.
The folding volume of a package of raw boards is equal to:
1.1 x 1 x 5 = 5.5 m³.
From Table 2 we find the laying density coefficient for raw hardwood boards with a thickness of 32 mm - 0.57.
Then the volume of dense wood of unedged boards in a package at a humidity of 20% (relative to the mass of absolutely dry wood) will be equal to:
5.5 x 0.57 = 3.135 m³.
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