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 standards volume fraction consumption:
- 14 – from 45 to 50%;
- 20 – about 52%;
- 25 – on average up to 57%;
- 34 – this is the diameter of timber timber, 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. At the same time, it is worth taking into account that a round forest of coniferous and deciduous trees will produce different yields of lumber from non-coniferous edged boards in m3.
Note! Coniferous wood species are considered the best option, due to the fact that they have a straight trunk and a 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. In this case, the remaining wood will not be immediately useful due to the fact that it requires additional process processing.
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.
Weight calculation cubic meter 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 cubic meters of timber you need to purchase if you know the required number of products, or, conversely, determine required quantity 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% edged.
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 the work, if the end result is planned to be 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 unedged 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 total number 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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When sawing wood, it is important to immediately calculate what the consumption will be, as this will affect the cost of lumber. Exit finished products may be different. It all depends on the quality of the wood used and whether measures are taken to optimize cutting. There are special measures to increase work efficiency, make the output better, and the quality of sawing higher. Before sawing, you need to pre-calculate everything. This is not as difficult as it might seem, but the consumption of round timber will be optimal and profitable to obtain an excellent result.
How to increase cutting efficiency
In order for the yield of lumber to be significant, it is necessary to use special measures to increase the efficiency of the process:
- The calculation should only be carried out when using special programs, manually it will have low efficiency, the percentage of defects will be high.
- The round timber must first be sorted so that processing is carried out correctly.
- For cutting you need to use equipment High Quality. Otherwise, the amount of waste will be large, and the quality of the resulting lumber will be low.
- It is best to cut wide lumber first; narrow lumber takes longer to process.
- It is not recommended to take long logs.
- Before work, you should set up the equipment.
The yield of finished lumber may vary. It must be remembered that at the first stage boards are obtained, then they are sorted. As a result, the percentage decreases even more; for example, for deciduous trees it can be only 10-20%.
How to optimize cutting
To increase the yield of lumber, the cutting process must be optimized. This applies primarily to those workpieces that have significant curvature. To cut a crooked round timber, you need to perform a number of steps:
- First, only suitable wood is selected for work. If the remaining logs have rot, sprouts, or cracks at the ends, then it is necessary to trim off some areas.
- If a rotten core is discovered during work, you can carefully remove it, and then saw the remaining part. This will allow you to avoid large losses and obtain boards with a length of 1 m or more with the required quality.
- It is recommended to use logs with a larger diameter so that the yield percentage is higher. The coefficient can be 1.48-2.1, but it all depends on the diameter, quality of the round timber, sorting, and equipment. For frame shops this coefficient will be 1.48-1.6, and for lines with milling equipment– 1.6 for large forest. With a round log diameter of 12 cm or more, the coefficient can exceed 2.1.
Volume of waste after sawing
To finished board came out with a high percentage, it is necessary to prepare everything correctly, the work must be carried out only in accordance with the technology. Roundwood of coniferous and deciduous species produces different yields. In the latter case, the volume is smaller, even if special additional equipment is used. Needles are considered more convenient for sawing, since their trunk is straight and the log has a larger diameter. Coniferous forest is not so susceptible to rotting, so there is less waste. For hardwood, 2 cutting technologies are usually used:
- using a band sawmill on Z75, Z63;
- into collapse, when a half-beam is cut out in the core of the material and passed through a multi-saw machine.
The volume of a band sawmill is 40-50%. When using technology for collapse, the yield is different, it can be increased up to 70%, but the costs of such work are higher. If you cut round timber, the length of which is 3 m, you can see that the percentage of scrap is quite large, and the remaining material requires processing. This applies to the bulk with boards 22x105(110, 115)x3000 mm. There are many options for such a marriage. For example, it could be a wormhole, which is no longer suitable for most jobs.
After sorting, the volume of hardwood material, which belongs to grade 0-2, will be only 20-30% of the amount obtained after sawing. This means that of the total mass of harvested round timber, the yield of normal boards will be only 10-20%. The remaining materials are mainly used for firewood. For coniferous round timber, the yield will be different, but attention must be paid to what average values of the resulting volume are observed.
Lumber output
In order for the yield of lumber to be optimal, numerous conditions must be taken into account. To calculate correctly, you can consider the example of round timber yield. The data was obtained from the real experience of specialists and from the performance of sawmills. This makes it possible to compare percentages and calculate optimal average numbers.
For conifers, the following solution is possible:
- For unedged boards and other unedged materials during sawing, the yield will be 70%. This is the amount of material obtained during processing, the amount of waste will be equal to 30%.
- For edged material, when using sawmills of 63, 65, 75, there will be a lower yield of lumber, only around 45%. For band sawmills, the yield is usually up to 55-60% of the finished material. If you use means to increase efficiency, you can reach 70%, although this requires extensive experience.
- From a circular sawmill you can get lumber in the amount of 70-75%, although using methods to increase efficiency it may well be 80-75%. But work experience is required.
According to GOST 8486-86, for grade 0-3, the yield percentage, not taking into account sorting, is approximately 70%.
Another 30% can be left for rejecting the finished material. The rejected material is not thrown away; it is used for the manufacture of other types of lumber, which allow for the presence of certain defects.
For deciduous roundwood, a different yield percentage is observed:
- For unedged material – 60%.
- For edged wood - up to 35-40%, since the curvature of the original deciduous wood is usually large.
The output can be increased; additional equipment is used for this. This can be a special multi-sawing machine, an edge trimming machine, or a slab machine. In this case, the yield of lumber will increase by about 20%. The given percentage is given based on data on obtaining boards of grade 0-4. When sorting grades 0-1, the percentage of lumber obtained is 10%. To get a cube of finished edged hardwood material, you need to cut 10 cubes of the original round wood.
The yield of lumber from roundwood may vary. It all depends on the original type of wood used by the sawmill. Special measures to increase efficiency allow you to get a larger percentage than is possible, but for this you must have some experience.
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 preserves 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 new.
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Dependence of volumetric output of trimming
lumber from the method of sawing logs
Ulasovets V.G. (USFTU. Yekaterinburg, RF)
The influence of the ways of log-sawing the volume outcome of edged boards was examined in this paper.
In sawmilling practice, the main method is to saw logs parallel to their longitudinal axis. The use of band saws and circular saws makes it possible to saw logs parallel to the generatrix, i.e. on the run. With the same location relative to the top end of the log, unedged boards of the same thickness, cut in different ways, will have different shape and volume. At the same time, the yield of edged rectangular lumber from them will also be different.
If the unedged board under study and the rectangular edged board obtained from it have the same thickness and length, then the volumes can be compared based on the ratio of their widths
where is the volumetric yield of edged boards from unedged ones, %;
b o- width of the edged rectangular board;
b n.o.- average width of the original unedged board.
We study the dependence of changes in volumetric output edged lumber from unedged logs from methods of sawing parallel to the longitudinal axis and parallel to the generatrix.
IN general view width of edged rectangular board b o for both cutting methods are calculated using the formula
,
(2)
Where r - radius of the log at the top;
e vn.v.- the distance from the center of the top end of the log to the inner surface of the board under study;
N= (A + u a)/2r- the thickness of the sawn board with an allowance for shrinkage in fractions of the top diameter of the log.
The average width of the original unedged board when sawing parallel to the longitudinal axis of the log (first method) is calculated using the following formulas:
Where TO– log run-off coefficient.
Let us draw some conclusions about the volumetric yield of edged lumber from unedged timber obtained in the first sawing method:
At constant e vn.v./r with an increase in the thickness of the unedged board, the width of the edged board decreases and the volume of the slats increases, so the volumetric yield of edged lumber decreases. For example, when e vn.v/r= 0.45 and log run-off coefficient TO=1.15 with a change in board thickness from 0.05 d up to 0.2 d the volumetric yield of the studied boards cut from logs with a truncated paraboloid trunk shape will decrease from 87.5 to 61.3%, and the corresponding volumetric yield of edged boards with a log trunk shape of a truncated cone will decrease from 87.8 to 61.5%;
With increase e vn.v /r the run-off coefficient of unedged boards increases and the volume of slats during trimming increases, so the volumetric output of edged lumber decreases. For example, when sawing a log with a run-out coefficient TO= 1.3 for boards thickness 0.15 d when changing value e vn.v /r=0.05to e vn.v /r=0.45 run-off coefficients of unedged boards vary accordingly from K d. 1 = 1.304 to K d. 1 =1.397, while the volumetric output (truncated paraboloid) will decrease from 82.0 to 66.6%, and the volumetric output (truncated cone) will decrease from 82.7 to 67.4%;
With an increase in the run-off coefficient of the original log, the run-off coefficient of the unedged board increases, and the volumetric yield of edged lumber decreases. For example, when cutting unedged boards with a thickness of 0.25 d at e vn.v/r=0.25 with an increase in the coefficients of logs running away from TO=1.05to TO=1.45 runoff coefficients of the corresponding unedged boards vary from K d.1 =1.058to K d.1 =1.511, and the volumetric yield of edged lumber (truncated paraboloid) decreases from 73.8 to 58.0%; volumetric yield (truncated cone) decreases from 73.9 to 59.1%;
As the diameter of the log at the top increases, the ratio of the thickness of the board to it decreases and the relative volume of the slats decreases, so the yield of edged lumber increases. For example, when cutting boards 32 mm thick at e vn.v/r= 0.3 from logs with run-off coefficient TO= 1.35 when the log diameters change from 20 to 50 cm, the ratio of the board thickness to the log diameter changes from 0.16 to 0.064, and the studied volumetric yield of edged lumber increases accordingly from 71.6 to 79.9%; the volumetric yield of edged lumber increases from 72.6 to 80.9%.
The average width of an unedged board when sawing parallel to the generatrix of a log (second method) is calculated using the following formulas:
For logs with a trunk shape in the form of a truncated paraboloid
For logs with a truncated cone shape
Let us draw some conclusions about the volumetric yield of edged lumber from unedged timber obtained in the second sawing method:
At a constant distance from the center of the apical end of the log to the inner face of the sawn board, with an increase in the thickness of the unedged board, the width of the edged and unedged boards decreases, the volume of the slats increases, and the volumetric yield of edged lumber decreases. For example, when e vn.v/r=0.45 and log run-off coefficient TO=1.15 with a change in board thickness from 0.05 d up to 0.2 d the volumetric output of edged boards (the shape of the log trunk is a truncated paraboloid) will decrease from 91.8 to 66.3%, and (the shape of the log trunk is a truncated cone) will decrease from 91.9 to 66.4%;
With increase e vn.v/r the runoff coefficient of the unedged board decreases, its width and volume, as well as the width and volume of the edged board, decrease, and the volumetric yield of edged lumber decreases. For example, when sawing a log with a runoff coefficient TO= 1.3 for boards 0.15 thick d when changing value e vn.v /r= 0.05to e vn.v /r= 0.45 runoff coefficients of unedged boards vary from K d. 2 = 1.238to K d.2 =1.18, and the volumetric yield of edged lumber (truncated paraboloid) will decrease from 85.0 to 75.5%, the volumetric yield of edged lumber (truncated cone) will decrease from 85.5 to 75.9%;
With an increase in the runoff coefficient of the original log, the runoff coefficient of the unedged board increases, and the volumetric yield of edged lumber decreases. For example, when sawing unedged boards with a thickness of 0.25 d at e vn.v /r=0.25 with an increase in the coefficients of logs running away from TO=1.05to TO= 1.45 runoff coefficients of the corresponding unedged boards vary from K d. 2 =1.036 up to K d. 2 = 1.286, and the volumetric yield of edged lumber produced from them decreases from 75.12 to 66.3%, respectively, the volumetric yield of lumber decreases from 75.13 to 67.0%;
With an increase in the diameter of the log, the ratio of the thickness of the board to the diameter of the log at the top decreases and the relative volume of the slats decreases, so the yield of edged lumber increases. For example, when cutting boards 32mm thick at e vn.v/r =0.3 from logs with run-off coefficient TO= 1.35 when the log diameters change from 20 to 50 cm, the volumetric yield of edged lumber increases from 78.8 to 85.9%, respectively, the volumetric yield increases from 79.4 to 86.6%.
Note that, just as when sawing a log parallel to the longitudinal axis, in the second sawing method the volumetric output of edged lumber from unedged timber obtained by cutting logs with a truncated cone shape of a trunk is slightly higher than when cutting logs with a trunk shape - a truncated paraboloid . This can be explained by the slightly larger volume of the rung zone of unedged boards cut from logs with a truncated paraboloid shape of the trunk, which turns into slats during the production of edged lumber.
It should be noted that in the second method, when sawing logs with a high runoff coefficient into boards with a thickness of no more than 0.1 d,with increase e vn.v/r There is an increase in the volumetric yield of edged lumber from unedged timber. For example, in the case of sawing a log having the shape of a trunk in the form of a truncated paraboloid, with a runoff coefficient TO= 1.5 per board thickness 0.05 d at values e vn.v=0, e vn.v/r= 0,1,e vn.v/r=0,2, e vn.v /r=0.3, the volumetric yield of edged lumber from unedged timber will correspondingly take values of 80.72, 81.52, 82.11, 82.48%, reaching a maximum at e vn.v/r = 0.38…0.387, respectively - 82.59%.
For logs with a trunk shape in the form of a truncated cone for the above conditions, the volumetric yield of edged lumber from unedged timber will correspondingly take values of 81.99, 82.73, 83.27, 83.58%, reaching a maximum at e vn.v/r= 0.36…0.37, respectively -83.64%.
The relative difference in the volumetric yield of edged lumber from the corresponding unedged timber obtained in both cutting methods is calculated by the formula
. (8)
Where V o . 2 - volume of edged board in the second method of sawing logs;
V o . 1 - volume of edged board in the first method of sawing logs.
When sawing logs using the compared methods, the relative difference in the volumetric yield of edged lumber from unedged lumber can be significant. For example, when sawing a log with a runoff coefficient TO= 1.25 for boards 0.1 thick d when the distance from the center of the top end of the log to the inner surface of the board changes e vn.v/r= 0...0.6, the relative difference in the volumetric yield of edged lumber from unedged timber changes: for logs with a truncated paraboloid trunk shape - from 1.7 to 15.9%; for logs with a truncated cone shape – from 1.6 to 15.1%.
The conducted studies indicate that it is economically profitable for enterprises producing long edged lumber, blanks and parts to cut logs parallel to the generatrix.