Determining the percentage of lumber yield when sawing timber, in particular round timber. How to optimize the yield of sawn timber from roundwood Yield percentage of finished log products

To obtain a high percentage of lumber from round logs, several different technologies, including certain cycles of actions. The time required for sawing round timber and the labor intensity of the process varies, depending on the chosen processing method, the location of the work, and the season. Thus, some enterprises build workshops for the primary processing of raw materials near the timber harvesting site and save on this.

Not only trunks, but also large branches are processed. Roundwood logs are sorted by size and presence of bark. The trunks that have not been sorted are subsequently used for rough work (making scaffolding, 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 meet the technical specifications. Defects in wood reduce the yield percentage finished products, and knots can damage the equipment.

Before sawing, trunks are often debarked (bark is removed using a special machine) - this process is optional, but is 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 improves;
• some enterprises do not accept slabs from unbarked logs for processing;
• the error in results when sorting wood using electronics is reduced.

Types of wood cutting

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

Radial - a cut along the radius, perpendicular to the growth rings, the pattern is uniform, the yield 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

For each specific case, a cutting method is selected.

Tumbling is the most economical, almost no waste, high percentage of finished timber. The output is unedged boards and two slabs.

With lumber - first you get a double-edged beam, unedged boards, and two slabs. Then the timber is sawn perpendicular to the cut into edged boards, along the edges two unedged boards and two slabs are obtained.

Sector - first, the log is sawn into 4–8 sectors, and then each of them into radial or tangential materials. Sometimes several unedged boards are cut in the center.

Break-up-segment - with this type of cutting, two or more unedged boards are cut in the center of the trunk, and edged one-sided boards are sawed from segments on the sides.

Beam-segment - similar to split-segment, only in the middle of the log a two-edged beam is cut, which is then sawn into edged boards. The yield of lumber is high.

Circular - after sawing off one or more unedged boards, the log is rotated 90 0 and the following boards are sawed off. This method is used when a large log is affected by heart rot in the center. With its help, healthy wood is separated from low-quality wood.

Aggregate - using milling tools and circular saws, along with high-quality lumber, the output is technological chips (instead of slabs and slats). Such complex forest processing allows for rational use of raw materials and labor costs. This results in waste-free production of finished lumber.

Necessary tool

The choice of tools depends on the quantity of planned finished products, their quality and product sizes. Most often, cutting is performed with a circular saw. At certain stages of production, the use of special machines is required.

A circular saw makes precise cuts in any direction, copes well with any size log, is suitable for professional and home use.

It is used for home use when it is necessary to prepare a small amount of lumber. It's easier to do more difficult jobs with a chainsaw than to buy expensive equipment. All you need for it is a special attachment, a barrel fastener and cutting guides.

Machines for removing bark. They are quite expensive, but with regular use in an enterprise where large volumes of work are performed, they quickly pay for themselves. They are not required to be used, but are desirable because they can provide a number of economic advantages and conveniences in the production process.

You will also need:

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

At enterprises with mass production, to obtain ultra-precise and high-quality products, entire complexes of modern equipment are installed, and sawing of wood is carried out of any complexity.

Sawing technological map

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

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

The percentage of lumber at the output is ready-to-use, useful wood. Waste is the raw material for producing MDF, chipboard, and fiberboard. These volumes will depend on the diameter of the tree, the types of solid wood products being manufactured, and the sawing option.

Percentage of round timber

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

By volume of transport. Each type of transport has its own forest cubic capacity calculated and determined. For example, a carriage holds 70.5 cubic meters of round wood. Then there will be 22.5 cubic meters of it in three cars. This method of calculation speeds up the acceptance of raw materials, this is especially important when large quantities received cargo. But there is a large error in the calculation results in this way.

Calculation based on the volume of one trunk. If the entire logging consists of timber of the same size, then by counting 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 the involvement of more workers to accept the cargo.

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

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

Dependence of the final yield percentage on 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 put into production only high-quality wood.
• Then select trunks with damage at the ends (rot, cracks) and trim these places.
• If there is a section of trunk with a rotten core, it must be removed and the remaining wood cut into lumber. They will be shorter, but of better quality.
• The circular cutting method is also suitable for obtaining high-quality boards.
• The yield percentage is higher when sawing timber with a larger diameter.

The yield also depends on the quality of the log, the type of wood, and the equipment used. New high-quality, well-tuned equipment allows you to process trunks with almost no losses.

The efficiency of timber cutting can be increased if special measures are taken in advance. To do this you need to make exact calculations using digital programs. If you do this manually, the percentage of output defects will be higher. It should be taken into account in advance that coniferous forest species produce a higher percentage of lumber output. Because their trunks are smooth, large, less susceptible to rotting and therefore almost free of defects. Deciduous large volume often discarded.

For rational use For wood, it is better to take short logs. But in domestic production Typically, trunks with a length of 4 m or more are taken for sawing. Due to their curvature, the output results in a large percentage of rejects.

Forest sawing is a cycle of actions using a variety of technologies aimed at obtaining lumber from round timber suitable for further use in industry. The duration and labor intensity of the process depend on the chosen method of processing round timber, as well as the time of year.

Tools and equipment

Barrels and big size branches. All material is divided into groups according to thickness and presence of bark. Often, timber processing enterprises have workshops near the harvesting site, in which machines for the initial processing of wood are installed.

Manual debarking of wood

Not past stage debarked wood can be used on floors or as ridge beam in the appropriate interior, or as a supporting device during construction.

Industrial debarking of forests

If another option for using the wood is planned, then sawing is carried out, resulting in the following segments:

• unedged and semi-edged (rough material from which the bases of the floor, walls or ceiling are mounted);
• edged (intended for finishing flooring).

The cutting can be carried out by a mobile organization that has all the necessary tool.

Wood cutting map

Rational use of the material is ensured by compliance with the cutting map. This allows you to reduce costs due to waste, the percentage of which the card can significantly reduce. The tools and types of forest processing equipment used depend on the volume, desired quality and size of the finished lumber.

The most commonly used are a circular saw and various machines:

• circular due circular saw allows you to make precise cuts in various directions. Suitable for both professional and home use, it copes well with above-average round timber diameters;
• chainsaw;
• machines for clean bark removal;
• sawing on a band sawmill makes it possible to process dense logs; it is considered the most popular, since the output is high-quality material and a small amount of waste;
• disk machine: production of double-edged timber and unedged boards;
• a frame sawmill does not require a foundation, the technology using it allows you to install the equipment in close proximity to the felling site;
• fine meter processed universal machines, the output produces high-quality building materials even from low-grade logs;
• sawing of round timber at a large woodworking enterprise should be carried out with the largest amount of lumber, differing from the rest in its special quality and precise dimensions. For this purpose, special lines are installed for sawing.

At the sawmill, timber and edged boards are obtained by cutting logs up to 7 m long and 15-80 cm in diameter along the longitudinal line. A circular saw has one or more disks and processes wood of different diameters according to their number.

If you need to process a small amount of wood at home, you can use a regular chainsaw.

Cutting wood

Before choosing a tool, you need to decide on the type of cut, focusing on the annual rings of the log. There are several types:

• radial (along the radius);
• tangential (the cut is parallel to one radius and touches the annual rings);
• the fibers are located parallel to the cutting being performed.

Among the cutting methods, the one that is most suitable for a particular case is selected:

1. Waddle. Sawing wood in this way is carried out for deciduous trees with a small trunk thickness, and is considered the simplest processing. Output: unedged elements and slabs.
2. If you have another forest processing machine, then it is possible to cut up to 65% of the material to produce edged boards of equal width. First, the double-edged timber and boards on the sides are cut, and then a certain amount of edged lumber is obtained from the timber.
3. More specific methods are sector and segment sawing. The number of elements in the first method varies from 4 to 8, and depends on the thickness of the trunk. After dividing, elements are cut from each sector along a tangential or radial line. The second method begins with the timber coming out of the central part, and boards are cut from the side segments in a tangential direction.
4. For individual cutting of wood, the circular method is suitable. It is based on turning the log along the longitudinal line by 90° after each sawn board. This allows you to monitor the quality of the wood and promptly remove affected areas of the trunk.

Manual work: using a chainsaw

For home cutting of several trunks, it is not advisable to purchase a tool whose cost is several times higher than the price of finished products. If you have the necessary skill, then it is more efficient and cheaper to do the whole necessary work a regular chainsaw, or chain equipment powered by electricity. Of course, such work requires much more physical effort and time, but the cost of the issue is significantly reduced.

Work for garden plot requires pruning fruit trees, and it also becomes possible to additionally produce material for outbuildings without resorting to the services of specialists, so any thrifty owner will prefer to buy a chainsaw. Most often, coniferous wood is harvested for the home, and this tool does an excellent job of cutting it. Thanks to straight trunks, it is easier to mark cutting lines, which increases the speed of work. Professionals, by the way, most often use a chainsaw, since it is more powerful than an electric one and can be used anywhere, regardless of whether there are power sources at the cutting or cutting site.

To use a chainsaw to cut logs, you will need a device such as a saw attachment, as well as cutting guides and base-trunk fasteners. The frame-shaped attachment is attached to the tool so that it remains possible to adjust the distance between the chain and the frame itself. This is done to make it possible to produce finished lumber of different thicknesses. For the role of a guide, you can take either a profile of the required length, or an even wooden plank with sufficient rigidity. A special chain is selected for the tool, designed to cut the trunk lengthwise. Its difference from the others lies in the teeth sharpened at a certain angle.

Before you start work, you need to not only prepare all the necessary tools. Regardless of whether a woodworking machine is intended for processing a trunk or hand tool, the first thing you need to do is familiarize yourself with the cutting map. This is done in order to minimize the percentage of waste and increase the yield of useful products.

The first thing you need to worry about when cutting longitudinally is the uniform density of the finished boards. To do this, a competent sawyer directs the tool from the east side of the log to the west, or in the opposite direction. This is explained by the higher density of round timber in its northern part than in the southern part.

Next, use a chainsaw to remove the slab from both sides so as to obtain a double-edged beam. It, in turn, is sawed in accordance with the cutting pattern chosen at the beginning of the work. The solution is an unedged board. If there is a certain percentage of defects in the trunk, then a circular cut is possible with the trunk turning at a right angle or 180°.

Quantity of finished material, cutting price

Exit useful material from coniferous and deciduous species differs in percentage. For lumber obtained from coniferous trees, the following indicators are characteristic:

• provided that the operation is carried out by a professional and a circular sawmill is used, the percentage of finished wood will be the highest (80-85%);
• the edged material produced by the machines averages 55-70%;
• When used with a chainsaw, an unedged board leaves up to 30% waste.

The figures are given without taking into account the finished culled timber, the amount of which can reach 30%. However, such material is used for products that allow certain defects.

Deciduous round timber produces 60% of the finished unedged timber and about 40% of the edged timber. This is explained by the initial curvature of the round timber. It is possible to increase the amount of products obtained: this will require forest processing machines of various types. A certain kind of device can increase the amount of lumber by 10-20%. For one cube of lumber you will need about 10 cubes of deciduous round timber. Installation price additional equipment will pay off the cost of the finished timber. Special lines provide greater volume, but their use is only advisable over a large area. The average price of sawing wood at a regular sawmill will be approximately 150-180 rubles per cubic meter of boards.

Sawing map

The sawing map is a calculation of the optimal amount of finished lumber from one log. You can calculate it yourself for each specific log diameter, or you can use a computer program that greatly facilitates the calculation, and the price of which is quite affordable.

Or the source could be a regular sawmill reference book. The result is a table that is used as a basis. The sawmill attachment should always be oriented to its data in order to obtain more lumber of any type of wood.

Lumber is obtained by cutting logs (blanks). In essence, this is lumber of a certain size with two plane-parallel sides (faces). Sawing can be either radial or tangential.

In Fig. 1 presented different kinds lumber - from plate to edged boards.

Figure 1. Types of lumber: a - plate; b - two-roll beam; c - not edged board; g- quarter; d - four-edged timber with wane; e - semi-edged board with wane; g - clean-edged timber; h - croaker; and - edged board; k - planed tongue and groove boards; 1- face; 2 - edge; 3 - rib; 4 - end; 5 - wane

The following elements are distinguished in lumber: layers, edges, ribs, ends. Face - the longitudinal wide side of the lumber, as well as any side of the lumber square section. The best face of lumber has the least amount of defects, best quality processing. The face of lumber facing the core is called the inner face, and the face facing the sapwood is called the outer face. Edge - the longitudinal narrow side of lumber. Edge - the line of intersection of two adjacent sides of lumber. End - the end transverse side of the lumber. Wane is not a mandatory element of lumber; it is, so to speak, an element of defective edged boards due to poor quality of the source material (log or workpiece).

Lumber is produced according to GOST 8486-86E:

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

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

The following are 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 double-edged).

Length of lumber: softwood no more than 6.5 m, hardwood no more than 5 m. For special structures, lumber up to 9 m long, made to special order, can be used. The thickness and width of lumber are determined by the assortment (Tables 1, 2, 3).

Table 1. Output standard edged lumber per 1 m 3 logs

Note:

1) When the grade of roundwood is increased to 1, the lumber yield standard increases by 3%.

2) When the grade of roundwood is reduced to grade 3, the lumber yield standard is reduced by 2%, to grade 4 - by 7%.

3) With a mixed supply of large and medium logs, the lumber yield standard is taken as the arithmetic mean between medium and large logs.

Table 2. Thickness and width of softwood lumber in mm

Table 3. Thickness and width of hardwood lumber in mm

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

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

The use of lumber from hardwood is allowed for rafter parts, internal stairs, interior wall and partition cladding, ceiling trim, soffits, gables, interior architectural details, millwork and finished 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.

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. Roundwood lumber yield is everything 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 timber timber, which differs in the most high value volume fraction equal to 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 is worth taking into account that a round forest of coniferous and deciduous trees will produce different yields of lumber from unedged 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:

1. Using band sawmill at 375 or 363.
2. 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.

TIMBER YIELD BASED ON FIR ROUND TIMBER VOLUME TABLES

Koptev Artem Sergeevich 1, Weiss Andrey Andreevich 2
1 Federal State Budgetary Educational Institution of Higher Education "Siberian State Technological University", Bachelor in Forestry
2 Federal State Budgetary Educational Institution of Higher Education "Siberian State Technological University", Doctor of Agricultural Sciences, Associate Professor of the Department of Forest Taxation, Forest Management and Geodesy

OUT OF LUMBER BASED ON THE TABLES OF VOLUMES OF ROUNDWOOD FIR

Koptev Artem Sergeevich 1, Weis Andrey Andreevich 2
1 Siberian state technological university, bachelor in "Forestry business"
2 Siberian state technological university, doctor of agricultural sciences, assistant professor of forest inventory, forest management and geodesy

Back in the second half of the twentieth century, in forest taxation it was considered advisable to determine volumes for practical purposes using special tables. From all the tables compiled greatest application In our country, we found A.A. Kründer’s tables, common for all breeds, without taking into account the location of the harvested assortments on the trunks. These tables were later recalculated by G.M. Tursky into the metric system, supplemented by N.P. Anuchin and approved as GOST 2708-44.

Other tables were also used in practice before. For example, Provatorov’s table, which was compiled without any basic taxation material, purely mathematically calculated the volumes of logs, assuming one constant run for logs of all species and categories.

Klimashevsky’s tables, as well as Provatorov’s tables, were characterized by the fact that the volumes of logs were calculated purely mathematically, assuming their division into five classes, respectively, with a run of 1/8, 1/4, 3/8, 1/3 and 5/ 8 tops by a fathom.

The tables of Tour, Arnold, Toursky, Rudzsky were characterized by the compilation of the volume of logs based on numerous observations of the run-off and volume of logs of different species, and the possibility of giving one general table for logs of all classes and species was recognized.

However, these tables had certain disadvantages. For example, the tables of Tour, Arnold, Tursky, Rudzki were not adapted to the normal taxation of logs separately and acceptable determined the volume only with joint taxation more logs when we should expect a smoothing out of the extremes in the average result.

Also, the tables did not provide that the accuracy of estimating logs is influenced by the degree of granularity of thickness steps for log diameters and the total length of logs. When taking a very large step for log diameters of 4 cm, tables for single logs or for a small number of them should give large errors due to the rounding of diameters.

In modern forestry practice, the relationship between the characteristics of the entire forest stand and the parameters of individual trees in this tree stand is known. For example, according to research, the density of the grown tree stand affects the quality of the timber. To improve the quality of timber, a greater density of the tree stand is needed in the early phase of rotation to reduce the growth of branches in the lower part of the trunk, their accelerated death and self-cleaning of the trunks. In the late phase of cutting rotation, a relatively sparse tree stand is desirable to clear branches and accelerate the overgrowth of nodes. As is known, the greater the density, the smaller the runoff and vice versa, the lower the density, the greater the runoff, which in turn, as is already clear from the presented material, greatly influences the accuracy of determining the volume of assortments.

It is also necessary to take into account the influence of felling on the characteristics of the renewed subsequent forest stand. It is known that thinning contributed to a significant increase in trunk diameter at breast level, height growth, crown-to-trunk size ratio, crown width, but led to a decrease in trunk height to diameter at breast height. The trunk run-off also increased significantly, and therefore the determination of the wood supply turned out to be overestimated by 2-15%, especially for trees in thinned stands.

International trade in timber products is developing very dynamically. According to FAO, global roundwood exports have increased by 8 million m 3 over the past decade in quantitative terms. This was facilitated by the constant growth of global consumption of lumber in various sectors of the economy and the increasing importance of wood as a natural, environmentally friendly universal material. International trade in unprocessed wood today is developing in the context of growing volumes of its consumption. The leading exporters of round timber in the world are Russia, New Zealand, USA, and the main importers of unprocessed wood are China, Austria, and Germany. The main factor in volume growth international trade Currently, there is an increase in wood consumption in the world, and in the next few years this trend in the world market will continue.

Experimental studies. The research was carried out in the Biryusinsky district forestry of the educational and experimental forestry enterprise of Siberian State Technical University. Measurements of Siberian fir round timber were taken at the lower warehouse. Subsequently, the volumes of round timber were established different ways. The yield of cubic meters of lumber from a log was determined using Table 1 below.

Table 1 - Determination of lumber yield

Note: When the roundwood grade increases to 1, the lumber yield standard increases by 3%. When the grade of roundwood is reduced to grade 3, the lumber yield standard is reduced by 2%, to grade 4 – by 7%. With a mixed supply of large and medium logs, the lumber yield standard is taken as the arithmetic mean between medium and large logs.

As can be seen from the table, approximately 50% of the volume of the entire log is lumber. It is worth noting that coniferous trees have a higher lumber yield than deciduous ones.

Below is a table showing how many cubic meters of lumber, wood waste and sawdust come out when using the calculation results using the truncated cone formula and tabular data (Table 2), as well as using the median section formula (Table 3). The volumes were found for one log and for one hundred logs. The difference between the two lumber yields is also shown as a percentage. The yield of lumber obtained by calculation using the truncated cone formula for the first table and the median section formula for the second is taken as 100%.

Additionally, the cost of lumber obtained from 100 logs was calculated, the volume of which was determined from tabular data and the truncated cone formula (Table 3), as well as from tabular data and the formula for the median section (Table 4). In addition, the difference between the costs of lumber has been established.

Conclusions. A comparative analysis showed that standard values ​​in most cases underestimate the volume of logs by thickness level in comparison with the truncated cone formula (-33.2-+6.4%). In the thicker part of the logs, this difference stabilizes and is about 10%. At the same time, in relation to the formula for the median section, the tabulated values ​​of fir logs in most cases overestimate the actual volume of round timber. In value terms, for 100 logs the difference can be (36 cm step) up to 60,000 rubles.

Thus, the use of the truncated cone formula makes it possible to significantly reduce the error in determining the volume of fir logs in relation to the local East Sayan mountain taiga region.

Table 2 - Lumber output

Continuation of table 2

Table 3 - Lumber output

Table 4 - Cost of lumber

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