Cross section of a log: the meaning of the elements

Every person who works with wood knows how important it is to always have accurate information about the material.

A detailed examination of the cut of a log can reveal its positive and negative sides.

To do this, all you need is a cross-section of a log, which can show the situation in full light better than any advertising.

Content and meaning

There are 2 types of cut criteria - full and reduced. For semi-professional work (making furniture at home or small handicrafts), a shortened list is quite sufficient, while for professional work (factory production, assessing the quality of wood for import-export, etc.) you need to know all 8 elements.

The abbreviated version looks like this (Figure 1):

(Picture 1). Abbreviated criterion for evaluating a log cut.

Bark (divided into internal and external dead bark).
Cambium (wood).
Lub.
Sapwood (young rings located close to the bark).
The core (in coniferous trees it is called the core, in deciduous trees it is called mature wood). Some tree species lack it, for example, yew, and instead have a cavity.
Tree rings.

A more complete version includes only 2 points more (Figure 2):

Core rays.
Core (several circles around the core, which have the highest strength values, and at the same time the lowest moisture turnover, which helps protect against rotting processes).

(Figure 2). Complete criterion for evaluating a wood cut.

A detailed examination of wood can reveal positive and negative aspects that affect its assessment, and at the same time the possibility of further use. The higher quality and harder the material, the higher it is valued by craftsmen, but everything without exception is used, because... There are very different areas of industry. Depending on the results of the cross-section, the trunk is cut into boards using a tangential or radial method.

Cutting equipment and features of its use

An example of wood processing with group circular saws. For longitudinal cutting of logs, the following categories of equipment are used:

Single band saws or circular saws are a traditional solution that has been used for a long time.
The group of frame saws is a more progressive solution that can significantly increase the productivity of raw material processing without compromising the quality of the finished product.

Let us consider in more detail the features of the application of the listed categories of equipment.

Custom sawing is a method that uses single saws. In this case, only one cut can be obtained in one saw pass. Therefore, the entire tree trunk can be cut in several passes.

Important: The advantage of individual cutting is the independence of each subsequent cut from the previous one. That is, sawing can be carried out in different planes. As a result, it becomes possible to more rationally use certain properties of different parts of the log.
None At the same time, this method is low-productivity and therefore not suitable for use in large woodworking enterprises.

Group sawing is a technological process in which a group of frame saws is used.
The advantage of this method is that the log is completely cut in one pass. This saves time and, as a result, reduces the cost of production. But you need to remember that group sawing is performed in one plane. Today, the following categories of equipment for group sawing are most widespread:

narrow-clearance vertical frames, machines with circular saws, milling saws (diameter of processed raw materials from 14 to 22 cm).
medium-clearance vertical frames (diameter from 24 to 48 cm)
wide-clearance vertical frames, double and quadruple bandsaw-type units (diameter of processed raw materials over 50 cm).

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Summarizing

Wood is actually a natural polymer, and its cells have a specific tubular shape, and are directed along the trunk. It is this factor that gives it a number of unique properties - low weight, high strength, low density, high elasticity, resistance to all kinds of aggressive chemical influences, etc.

The full cross-section of a log is formed only over time, because Initially, the core of the seedling is almost always not formed, the bark is completely homogeneous, and natural protection is almost completely absent. During the growth process, the core changes, becoming harder and not susceptible to rotting.

By making a section of a log, you can see in detail all its main characteristics, after which you can accurately assign each part of it to a specific industry. But often this factor remains unattended, which is why very good wood is cut into edged boards.

Features of wood processing

Cutting chart for automated wood processing

The instructions for processing raw materials and obtaining lumber products consist of a number of technological operations, including longitudinal cutting of logs, trimming lumber and cutting to width, sorting by standard sizes, sorting by quality of workmanship, drying and storage.

Each of the listed stages is important from the point of view of the quality of the finished product. But cutting is the most labor-intensive and critical stage, during which the main characteristics of the finished lumber are formed.

Slicing diagram for common lumber products

Drawing up a plan for cutting logs into lumber (choosing a suitable processing method) depends on the type of wood, the size of the raw material, the degree of humidity, the density and hardness and many other factors. Of course, the method of processing raw materials is determined to a large extent based on the level of technical equipment of the enterprise.

Let's consider what equipment is used for industrial sawing of wood and what methods are relevant for each category of this equipment.

Cutting equipment and features of its use

An example of wood processing with group circular saws

The following categories of equipment are used for longitudinal cutting of logs:

Single band saws or circular saws are a traditional solution that has been used for a long time.
The group of frame saws is a more progressive solution that can significantly increase the productivity of raw material processing without compromising the quality of the finished product.

Let us consider in more detail the features of the application of the listed categories of equipment.

Custom sawing is a method that uses single saws. In this case, only one cut can be obtained in one saw pass. Therefore, the entire tree trunk can be cut in several passes.

Important: The advantage of individual cutting is the independence of each subsequent cut from the previous one. That is, sawing can be carried out in different planes. As a result, it becomes possible to more rationally use certain properties of different parts of the log.

At the same time, this method is low-productivity and therefore not suitable for use in large woodworking enterprises.

Group sawing is a technological process in which a group of frame saws is used. The advantage of this method is that the log is completely cut in one pass. This saves time and, as a result, reduces the cost of production. But you need to remember that group sawing is performed in one plane. Today, the following categories of equipment for group sawing are most widespread:

narrow-clearance vertical frames, machines with circular saws, milling saws (diameter of processed raw materials from 14 to 22 cm).
medium-clearance vertical frames (diameter from 24 to 48 cm)
wide-clearance vertical frames, double and quadruple bandsaw-type units (diameter of processed raw materials over 50 cm).

Basic methods of longitudinal sawing

This is what the log cutting table looks like on a band sawmill

So, now that we have examined the current methods of processing wood raw materials using special equipment, let’s consider the features of the implementation of these methods.

In the modern woodworking industry, the following cutting methods are used:

“Waddle” is a method of sawing logs in which the cutting planes are parallel to each other. In accordance with the arrangement of lumber in the log, the core board or timber is distinguished; central boards, one of the planes of which runs along the longitudinal axis of the log; side boards.

The photo shows a tree trunk installed in a slitting machine

Important: This method of processing wood raw materials is considered the simplest and least labor-intensive. But you need to take into account that the finished wooden boards are unedged, and therefore you will additionally have to make a cross-section of the log.

“With lumber” - this method allows you to get a lumber with two edges. The rest of the log is sawn into unedged side boards and flooring. That is, cutting is performed not in one, but in two passes. Moreover, the type of saws used for the first and second passes differs both in the number of cutting surfaces and in their direction.

Band saw cutting edge

The equipment on which the timber is made is called the first row machine, and the equipment by which the timber is cut into individual boards is called the second row machine.

The “sector” method, during which the log is cut into separate sectors, from which boards are subsequently made. Sawing using this method is performed in one pass, when the cutting tools are used sequentially or in several passes, when at the initial stage longitudinal sectors are obtained, and at subsequent stages these sectors are divided into lumber. The sector method is relevant for the production of lumber for radial and tangential sawing. In accordance with the diameter of the log and the required dimensions of the workpiece, sawing is performed only into quarters or into quarters, followed by cutting into smaller sectors. The disadvantages of this method include labor intensity, since the log cutting map is drawn up individually. In addition, when processing wood raw materials, a large amount of waste is generated.
The segment method involves sawing the trunk into longitudinal segments, which, in turn, are cut into boards of the required size.
The segment-breaker method involves the simultaneous production of segments and sawing them into lumber of the required size in one pass
The segment-beam method, in which the side segments are simultaneously sawed out, while a double-edged beam is obtained from the middle (central) part. The method involves cutting in two passes. During the first pass, the log is divided into beams and side segments. During the second pass, the segments are divided into smaller boards.
Circular sawing involves processing a log in which the boards are sawn off sequentially. During processing, the workpiece rotates around its axis after the next board is sawn off. Due to the labor intensity and individual approach, circular sawing is practically not used on an industrial scale.
The aggregate method involves preliminary milling of a wooden log, after which the resulting beam with a square cross-section is cut into the required number of boards. During milling, a large amount of technological chips is formed, which, in turn, is used for the production of particle boards or fibreboards.

Features of cross cutting

The most common configuration of cross-cutting machines

The cross section of a log is called trimming and is performed with special circular saws. Despite the fact that the price of lumber increases due to trimming, this stage is mandatory during industrial wood processing. Cross cutting is performed after the longitudinal sawing of the log is completed.

Lumber, upon completion of drying, often has simple, transverse and wavy curvatures. Such deformations are difficult to correct with your own hands. To reduce the degree of deformation of lumber, trimming is performed, during which part of the wood that has undergone curvature is simply cut off.

Automated line for cutting lumber

To perform these works, a cross-cutting machine is used in the form of a frame with a bottom-mounted saw. During cross-cutting, technological waste is generated, which can be processed into chips and used for the production of particle boards. The location of the cut is determined in accordance with the type of assortment and taking into account the defects of the processed lumber.

Methods for performing cross cutting

Cross-cutting machine in an industrial workshop

Currently, domestic and foreign manufacturers produce a wide range of cross-cutting machines.

In accordance with the configuration of the equipment and the degree of its automation, several trimming options can be performed:

Trimming beams and boards in a stack at a given constant length. This option is used in the manufacture of various carpentry products (doors, windows, stairs, etc.), laminated veneer lumber and structural elements for wooden house construction.
Trimming boards of different lengths. During this technological process, the boards are fed to the working tool, where they are automatically measured. Next, the control unit selects the optimal combination of workpieces that can be cut in one pass in accordance with the given specification.
Trimming with removal of defects with variable length of finished products. This equipment configuration allows you to minimize the volume of knots, rot, pigment spots and mechanical deformations by cutting off problem areas from the end of the workpiece. This option is widely used in the manufacture of furniture facades, where it is possible to glue lamellas to obtain a solid slab. Choosing this trimming option allows you to reduce the volume of production waste to a minimum and thus reduce the cost of the finished product.
Trimming with removal of defects with fixed standard sizes of finished products. In this case, all workpieces are cut to the same length according to specification.

Taking into account the peculiarities of the technological process, it should be noted that the products obtained in this way are the most expensive, since a large amount of waste remains.

Basic methods of longitudinal sawing

None In the modern woodworking industry, the following cutting methods are used:

“Waddle” is a method of sawing logs in which the cutting planes are parallel to each other. In accordance with the arrangement of lumber in the log, the core board or timber is distinguished; central boards, one of the planes of which runs along the longitudinal axis of the log; side boards.

The photo shows a tree trunk installed in a slitting machine.

Important: This method of processing wood raw materials is considered the simplest and least labor-intensive. But you need to take into account that the finished wooden boards are unedged, and therefore you will additionally have to make a cross-section of the log.

“With lumber” - this method allows you to get a lumber with two edges. The rest of the log is sawn into unedged side boards and flooring. That is, cutting is performed not in one, but in two passes. Moreover, the type of saws used for the first and second passes differs both in the number of cutting surfaces and in their direction.

Band saw cutting edge The equipment on which the timber is made is called the first row machine, and the equipment by which the timber is cut into individual boards is called the second row machine.

The “sector” method, during which the log is cut into separate sectors, from which boards are subsequently made.
Sawing using this method is performed in one pass, when the cutting tools are used sequentially or in several passes, when at the initial stage longitudinal sectors are obtained, and at subsequent stages these sectors are divided into lumber. The sector method is relevant for the production of lumber for radial and tangential sawing. In accordance with the diameter of the log and the required dimensions of the workpiece, sawing is performed only into quarters or into quarters, followed by cutting into smaller sectors. The disadvantages of this method include labor intensity, since the log cutting map is drawn up individually. In addition, when processing wood raw materials, a large amount of waste is generated.
The segment method involves sawing the trunk into longitudinal segments, which, in turn, are cut into boards of the required size.
The segment-breaker method involves the simultaneous production of segments and sawing them into lumber of the required size in one pass
The segment-beam method, in which the side segments are simultaneously sawed out, while a double-edged beam is obtained from the middle (central) part. The method involves cutting in two passes. During the first pass, the log is divided into beams and side segments. During the second pass, the segments are divided into smaller boards.
Circular sawing involves processing a log in which the boards are sawn off sequentially. During processing, the workpiece rotates around its axis after the next board is sawn off. Due to the labor intensity and individual approach, circular sawing is practically not used on an industrial scale.
The aggregate method involves preliminary milling of a wooden log, after which the resulting beam with a square cross-section is cut into the required number of boards. During milling, a large amount of technological chips is formed, which, in turn, is used for the production of particle boards or fibreboards.

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Features of cross cutting

The most common configuration of cross-cutting machines. The cross-section of a log is called cross-cutting and is performed with special circular saws. Despite the fact that the price of lumber increases due to trimming, this stage is mandatory during industrial wood processing. Cross cutting is performed after the longitudinal sawing of the log is completed.

Automated line for cutting lumber To perform this work, a cross-cut machine is used in the form of a frame with a bottom-mounted saw. During cross-cutting, technological waste is generated, which can be processed into chips and used for the production of particle boards. The location of the cut is determined in accordance with the type of assortment and taking into account the defects of the processed lumber.

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